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< !DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
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<chapter id= 'extendpoky' >
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<title > Common Tasks</title>
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<para >
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This chapter describes standard tasks such as adding new
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software packages, extending or customizing images, and porting work to
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new hardware (adding a new machine).
The chapter also describes how to combine multiple
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versions of library files into a single image, how to handle a package name alias, and
gives advice about how to make changes to the Yocto Project to achieve the best results.
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</para>
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<section id= "understanding-and-creating-layers" >
<title > Understanding and Creating Layers</title>
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<para >
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The OpenEmbedded build system supports organizing <link linkend= 'metadata' > metadata</link>
into multiple layers.
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Layers allow you to isolate different types of customizations from each other.
You might find it tempting to keep everything in one layer when working on a single project.
However, the more modular you organize your metadata, the easier it is to cope with future changes.
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</para>
<para >
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To illustrate how layers are used to keep things modular, consider machine customizations.
These types of customizations typically reside in a BSP Layer.
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Furthermore, the machine customizations should be isolated from recipes and metadata that support
a new GUI environment, for example.
This situation gives you a couple of layers: one for the machine configurations, and one for the
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GUI environment.
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It is important to understand, however, that the BSP layer can still make machine-specific
additions to recipes within the GUI environment layer without polluting the GUI layer itself
with those machine-specific changes.
You can accomplish this through a recipe that is a BitBake append
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(<filename > .bbappend</filename> ) file, which is described later in this section.
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</para>
<para >
</para>
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<section id= 'yocto-project-layers' >
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<title > Layers</title>
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<para >
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The Source Directory contains several layers right out of the
box.
You can easily identify layers that ship with a
Yocto Project release in the Source Directory by their
folder names.
Folders that are layers begin with the string
<filename > meta</filename> .
<note >
It is not a requirement that a layer begins with the
string <filename > meta</filename> .
</note>
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For example, when you set up the <link linkend= 'source-directory' > Source Directory</link>
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structure, you will see several layers: <filename > meta</filename> ,
<filename > meta-hob</filename> , <filename > meta-skeleton</filename> ,
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<filename > meta-yocto</filename> , and <filename > meta-yocto-bsp</filename> .
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Each of these folders is a layer.
</para>
<para >
Furthermore, if you set up a local copy of the <filename > meta-intel</filename> Git repository
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and then explore that folder, you will discover many BSP layers within the
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<filename > meta-intel</filename> layer.
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For more information on BSP layers, see the
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"<ulink url= '&YOCTO_DOCS_BSP_URL;#bsp-layers' > BSP Layers</ulink> "
section in the Yocto Project Board Support Package (BSP) Developer's Guide.
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</para>
</section>
<section id= 'creating-your-own-layer' >
<title > Creating Your Own Layer</title>
<para >
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It is very easy to create your own layer to use with the OpenEmbedded build system.
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Follow these general steps to create your layer:
<orderedlist >
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<listitem > <para > <emphasis > Check Existing Layers:</emphasis> Before creating a new layer,
you should be sure someone has not already created a layer containing the metadata
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you need.
You can see the
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<ulink url= '&OE_HOME_URL;/wiki/LayerIndex' > <filename > LayerIndex</filename> </ulink>
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for a list of layers from the OpenEmbedded community that can be used in the
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Yocto Project.</para> </listitem>
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<listitem > <para > <emphasis > Create a Directory:</emphasis>
Create the directory for your layer.
While not strictly required, prepend the name of the
folder with the string <filename > meta</filename> .
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For example:
<literallayout class= 'monospaced' >
meta-mylayer
meta-GUI_xyz
meta-mymachine
</literallayout> </para> </listitem>
<listitem > <para > <emphasis > Create a Layer Configuration File:</emphasis> Inside your new
layer folder, you need to create a <filename > conf/layer.conf</filename> file.
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It is easiest to take an existing layer configuration file and copy that to your
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layer's <filename > conf</filename> directory and then modify the file as needed.</para>
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<para > The <filename > meta-yocto-bsp/conf/layer.conf</filename> file demonstrates the
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required syntax:
<literallayout class= 'monospaced' >
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# We have a conf and classes directory, add to BBPATH
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BBPATH := "${BBPATH}:${LAYERDIR}"
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# We have a packages directory, add to BBFILES
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BBFILES := "${BBFILES} ${LAYERDIR}/recipes-*/*/*.bb \
${LAYERDIR}/recipes-*/*/*.bbappend"
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BBFILE_COLLECTIONS += "yoctobsp"
BBFILE_PATTERN_yoctobsp := "^${LAYERDIR}/"
BBFILE_PRIORITY_yoctobsp = "5"
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</literallayout> </para>
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<para > Here is an explanation of the example:
<itemizedlist >
<listitem > <para > The configuration and
classes directory is appended to
<ulink url= '&YOCTO_DOCS_REF_URL;#var-BBPATH' > <filename > BBPATH</filename> </ulink> .
<note >
All non-distro layers, which include all BSP
layers, are expected to append the layer
directory to the
<filename > BBPATH</filename> .
On the other hand, distro layers, such as
<filename > meta-yocto</filename> , can choose
to enforce their own precedence over
<filename > BBPATH</filename> .
For an example of that syntax, see the
<filename > layer.conf</filename> file for
the <filename > meta-yocto</filename> layer.
</note> </para> </listitem>
<listitem > <para > The recipes for the layers are
appended to
<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-BBFILES' > BBFILES</ulink> </filename> .
</para> </listitem>
<listitem > <para > The
<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-BBFILE_COLLECTIONS' > BBFILE_COLLECTIONS</ulink> </filename>
variable is then appended with the layer name.
</para> </listitem>
<listitem > <para > The
<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-BBFILE_PATTERN' > BBFILE_PATTERN</ulink> </filename>
variable is set to a regular expression and is
used to match files from
<filename > BBFILES</filename> into a particular
layer.
In this case, immediate expansion of
<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-LAYERDIR' > LAYERDIR</ulink> </filename>
sets <filename > BBFILE_PATTERN</filename> to the
layer's path.</para> </listitem>
<listitem > <para > The
<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-BBFILE_PRIORITY' > BBFILE_PRIORITY</ulink> </filename>
variable then assigns a priority to the layer.
Applying priorities is useful in situations
where the same package might appear in multiple
layers and allows you to choose what layer
should take precedence.</para> </listitem>
</itemizedlist> </para>
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<para > Note the use of the
<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-LAYERDIR' > LAYERDIR</ulink> </filename>
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variable with the immediate expansion operator.
The <filename > LAYERDIR</filename> variable expands to the directory of the current layer and
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requires the immediate expansion operator so that BitBake does not wait to expand the variable
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when it's parsing a different directory.</para>
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<para > Through the use of the <filename > BBPATH</filename> variable,
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BitBake locates <filename > .bbclass</filename> files, configuration
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files, and files that are included with <filename > include</filename>
and <filename > require</filename> statements.
For these cases, BitBake uses the first file with the matching name found in
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<filename > BBPATH</filename> .
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This is similar to the way the <filename > PATH</filename> variable is used for binaries.
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We recommend, therefore, that you use unique <filename > .bbclass</filename>
and configuration file names in your custom layer.</para> </listitem>
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<listitem > <para > <emphasis > Add Content:</emphasis> Depending on the type of layer,
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add the content.
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If the layer adds support for a machine, add the machine configuration in
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a <filename > conf/machine/</filename> file within the layer.
If the layer adds distro policy, add the distro configuration in a
<filename > conf/distro/</filename> file with the layer.
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If the layer introduces new recipes, put the recipes you need in
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<filename > recipes-*</filename> subdirectories within the layer.
<note > In order to be compliant with the Yocto Project, a layer must contain
a <ulink url= '&YOCTO_DOCS_BSP_URL;#bsp-filelayout-readme' > README file.</ulink>
</note> </para> </listitem>
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</orderedlist>
</para>
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<para >
To create layers that are easier to maintain, you should consider the following:
<itemizedlist >
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<listitem > <para > Avoid "overlaying" entire recipes from other layers in your
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configuration.
In other words, don't copy an entire recipe into your layer and then modify it.
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Use <filename > .bbappend</filename> files to override the parts of the
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recipe you need to modify.</para> </listitem>
<listitem > <para > Avoid duplicating include files.
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Use <filename > .bbappend</filename> files for each recipe that uses an include
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file.
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Or, if you are introducing a new recipe that requires the included file, use the
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path relative to the original layer directory to refer to the file.
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For example, use <filename > require recipes-core/somepackage/somefile.inc</filename>
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instead of <filename > require somefile.inc</filename> .
If you're finding you have to overlay the include file, it could indicate a
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deficiency in the include file in the layer to which it originally belongs.
If this is the case, you need to address that deficiency instead of overlaying
the include file.
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For example, consider how Qt 4 database support plug-ins are configured.
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The Source Directory does not have
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MySQL or PostgreSQL, however OpenEmbedded's
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layer <filename > meta-oe</filename> does.
Consequently, <filename > meta-oe</filename> uses <filename > .bbappend</filename>
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files to modify the <filename > QT_SQL_DRIVER_FLAGS</filename> variable to enable
the appropriate plugins.
This variable was added to the <filename > qt4.inc</filename> include file in
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the Source Directory specifically to allow the <filename > meta-oe</filename> layer
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to be able to control which plugins are built.</para> </listitem>
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</itemizedlist>
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</para>
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<para >
We also recommend the following:
<itemizedlist >
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<listitem > <para > Store custom layers in a Git repository that uses the
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<filename > meta-< layer_name> </filename> format.</para> </listitem>
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<listitem > <para > Clone the repository alongside other <filename > meta</filename>
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directories in the
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<link linkend= 'source-directory' > Source Directory</link> .</para> </listitem>
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</itemizedlist>
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Following these recommendations keeps your Source Directory and
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its configuration entirely inside the Yocto Project's core base.
</para>
</section>
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<section id= 'enabling-your-layer' >
<title > Enabling Your Layer</title>
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<para >
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Before the OpenEmbedded build system can use your new layer, you need to enable it.
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To enable your layer, simply add your layer's path to the
<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-BBLAYERS' > BBLAYERS</ulink> </filename>
variable in your <filename > conf/bblayers.conf</filename> file, which is found in the
<link linkend= 'build-directory' > Build Directory</link> .
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The following example shows how to enable a layer named <filename > meta-mylayer</filename> :
<literallayout class= 'monospaced' >
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LCONF_VERSION = "6"
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BBPATH = "${TOPDIR}"
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BBFILES ?= ""
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BBLAYERS ?= " \
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$HOME/poky/meta \
$HOME/poky/meta-yocto \
$HOME/poky/meta-yocto-bsp \
$HOME/poky/meta-mylayer \
"
BBLAYERS_NON_REMOVABLE ?= " \
$HOME/poky/meta \
$HOME/poky/meta-yocto \
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"
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</literallayout>
</para>
<para >
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BitBake parses each <filename > conf/layer.conf</filename> file as specified in the
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<filename > BBLAYERS</filename> variable within the <filename > conf/bblayers.conf</filename>
file.
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During the processing of each <filename > conf/layer.conf</filename> file, BitBake adds the
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recipes, classes and configurations contained within the particular layer to the source
directory.
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</para>
</section>
<section id= 'using-bbappend-files' >
<title > Using .bbappend Files</title>
<para >
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Recipes used to append metadata to other recipes are called BitBake append files.
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BitBake append files use the <filename > .bbappend</filename> file type suffix, while
the corresponding recipes to which metadata is being appended use the
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<filename > .bb</filename> file type suffix.
</para>
<para >
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A <filename > .bbappend</filename> file allows your layer to make additions or
changes to the content of another layer's recipe without having to copy the other
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recipe into your layer.
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Your <filename > .bbappend</filename> file resides in your layer, while the underlying
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<filename > .bb</filename> recipe file to which you are appending metadata
resides in a different layer.
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</para>
<para >
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Append files must have the same root name as the corresponding recipe.
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For example, the append file <filename > someapp_&DISTRO; .bbappend</filename> must
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apply to <filename > someapp_&DISTRO; .bb</filename> .
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This means the original recipe and append file names are version number-specific.
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If the corresponding recipe is renamed to update to a newer version, the
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underlying <filename > .bbappend</filename> file must be renamed as well.
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During the build process, BitBake displays an error on starting if it detects a
<filename > .bbappend</filename> file that does not have a corresponding recipe
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with a matching name.
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See the
<ulink url= '&YOCTO_DOCS_REF_URL;#var-BB_DANGLINGAPPENDS_WARNONLY' > <filename > BB_DANGLINGAPPENDS_WARNONLY</filename> </ulink>
variable for information on how to handle this error.
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</para>
<para >
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Being able to append information to an existing recipe not only avoids duplication,
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but also automatically applies recipe changes in a different layer to your layer.
If you were copying recipes, you would have to manually merge changes as they occur.
</para>
<para >
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As an example, consider the main formfactor recipe and a corresponding formfactor
append file both from the
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<link linkend= 'source-directory' > Source Directory</link> .
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Here is the main formfactor recipe, which is named <filename > formfactor_0.0.bb</filename> and
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located in the "meta" layer at <filename > meta/recipes-bsp/formfactor</filename> :
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<literallayout class= 'monospaced' >
DESCRIPTION = "Device formfactor information"
SECTION = "base"
LICENSE = "MIT"
LIC_FILES_CHKSUM = "file://${COREBASE}/LICENSE;md5=3f40d7994397109285ec7b81fdeb3b58 \
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file://${COREBASE}/meta/COPYING.MIT;md5=3da9cfbcb788c80a0384361b4de20420"
PR = "r20"
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SRC_URI = "file://config file://machconfig"
S = "${WORKDIR}"
PACKAGE_ARCH = "${MACHINE_ARCH}"
INHIBIT_DEFAULT_DEPS = "1"
do_install() {
# Only install file if it has a contents
install -d ${D}${sysconfdir}/formfactor/
install -m 0644 ${S}/config ${D}${sysconfdir}/formfactor/
if [ -s "${S}/machconfig" ]; then
install -m 0644 ${S}/machconfig ${D}${sysconfdir}/formfactor/
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fi
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}
</literallayout>
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Here is the append file, which is named <filename > formfactor_0.0.bbappend</filename> and is from the
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Crown Bay BSP Layer named <filename > meta-intel/meta-crownbay</filename> .
The file is in <filename > recipes-bsp/formfactor</filename> :
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<literallayout class= 'monospaced' >
FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
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PRINC := "${@int(PRINC) + 2}"
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</literallayout>
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This example adds or overrides files in
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<ulink url= '&YOCTO_DOCS_REF_URL;#var-SRC_URI' > <filename > SRC_URI</filename> </ulink>
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within a <filename > .bbappend</filename> by extending the path BitBake uses to search for files.
The most reliable way to do this is by prepending the
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<filename > FILESEXTRAPATHS</filename> variable.
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For example, if you have your files in a directory that is named the same as your package
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(<ulink url= '&YOCTO_DOCS_REF_URL;#var-PN' > <filename > PN</filename> </ulink> ),
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you can add this directory by adding the following to your <filename > .bbappend</filename> file:
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<literallayout class= 'monospaced' >
FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
</literallayout>
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Using the immediate expansion assignment operator <filename > :=</filename> is important because
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of the reference to <filename > THISDIR</filename> .
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The trailing colon character is important as it ensures that items in the list remain
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colon-separated.
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<note > <para > BitBake automatically defines the
<filename > THISDIR</filename> variable.
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You should never set this variable yourself.
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Using <filename > _prepend</filename> ensures your path will
be searched prior to other paths in the final list.</para>
<para > Also, not all append files add extra files.
Many append files simply exist to add build options
(e.g. <filename > systemd</filename> ).
For these cases, it is not necessary to use the
"_prepend" part of the statement.</para>
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</note>
</para>
</section>
<section id= 'prioritizing-your-layer' >
<title > Prioritizing Your Layer</title>
<para >
Each layer is assigned a priority value.
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Priority values control which layer takes precedence if there are recipe files with
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the same name in multiple layers.
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For these cases, the recipe file from the layer with a higher priority number takes precedence.
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Priority values also affect the order in which multiple <filename > .bbappend</filename> files
for the same recipe are applied.
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You can either specify the priority manually, or allow the build system to calculate it
based on the layer's dependencies.
</para>
<para >
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To specify the layer's priority manually, use the
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<ulink url= '&YOCTO_DOCS_REF_URL;#var-BBFILE_PRIORITY' > <filename > BBFILE_PRIORITY</filename> </ulink>
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variable.
For example:
<literallayout class= 'monospaced' >
BBFILE_PRIORITY := "1"
</literallayout>
</para>
<note >
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<para > It is possible for a recipe with a lower version number
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<ulink url= '&YOCTO_DOCS_REF_URL;#var-PV' > <filename > PV</filename> </ulink>
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in a layer that has a higher priority to take precedence.</para>
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<para > Also, the layer priority does not currently affect the precedence order of
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<filename > .conf</filename> or <filename > .bbclass</filename> files.
Future versions of BitBake might address this.</para>
</note>
</section>
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<section id= 'managing-layers' >
<title > Managing Layers</title>
<para >
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You can use the BitBake layer management tool to provide a view into the structure of
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recipes across a multi-layer project.
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Being able to generate output that reports on configured layers with their paths and
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priorities and on <filename > .bbappend</filename> files and their applicable recipes
can help to reveal potential problems.
</para>
<para >
Use the following form when running the layer management tool.
<literallayout class= 'monospaced' >
$ bitbake-layers < command> [arguments]
</literallayout>
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The following list describes the available commands:
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<itemizedlist >
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<listitem > <para > <filename > <emphasis > help:</emphasis> </filename>
Displays general help or help on a specified command.</para> </listitem>
<listitem > <para > <filename > <emphasis > show-layers:</emphasis> </filename>
Show the current configured layers.</para> </listitem>
<listitem > <para > <filename > <emphasis > show-recipes:</emphasis> </filename>
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Lists available recipes and the layers that provide them.
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</para> </listitem>
<listitem > <para > <filename > <emphasis > show-overlayed:</emphasis> </filename>
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Lists overlayed recipes.
A recipe is overlayed when a recipe with the same name exists in another layer
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that has a higher layer priority.
</para> </listitem>
<listitem > <para > <filename > <emphasis > show-appends:</emphasis> </filename>
Lists <filename > .bbappend</filename> files and the recipe files to which
they apply.</para> </listitem>
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<listitem > <para > <filename > <emphasis > flatten:</emphasis> </filename>
Flattens the layer configuration into a separate output directory.
Flattening your layer configuration builds a "flattened" directory that contains
the contents of all layers, with any overlayed recipes removed and any
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<filename > .bbappend</filename> files appended to the corresponding recipes.
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You might have to perform some manual cleanup of the flattened layer as follows:
<itemizedlist >
<listitem > <para > Non-recipe files (such as patches) are overwritten.
The flatten command shows a warning for these files.</para> </listitem>
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<listitem > <para > Anything beyond the normal layer setup has been added to
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the <filename > layer.conf</filename> file.
Only the lowest priority layer's <filename > layer.conf</filename> is used.
</para> </listitem>
<listitem > <para > Overridden and appended items from <filename > .bbappend</filename>
files need to be cleaned up.
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The contents of each <filename > .bbappend</filename> end up in the
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flattened recipe.
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However, if there are appended or changed variable values, you need to tidy
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these up yourself.
Consider the following example.
Here, the <filename > bitbake-layers</filename> command adds the line
<filename > #### bbappended ...</filename> so that you know where the following
lines originate:
<literallayout class= 'monospaced' >
...
DESCRIPTION = "A useful utility"
...
EXTRA_OECONF = "--enable-something"
...
#### bbappended from meta-anotherlayer ####
DESCRIPTION = "Customized utility"
EXTRA_OECONF += "--enable-somethingelse"
</literallayout>
Ideally, you would tidy up these utilities as follows:
<literallayout class= 'monospaced' >
...
DESCRIPTION = "Customized utility"
...
EXTRA_OECONF = "--enable-something --enable-somethingelse"
...
</literallayout> </para> </listitem>
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</itemizedlist> </para> </listitem>
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</itemizedlist>
</para>
</section>
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</section>
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<section id= 'usingpoky-extend-customimage' >
<title > Customizing Images</title>
<para >
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You can customize images to satisfy particular requirements.
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This section describes several methods and provides guidelines for each.
</para>
<section id= 'usingpoky-extend-customimage-custombb' >
<title > Customizing Images Using Custom .bb Files</title>
<para >
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One way to get additional software into an image is to create a custom image.
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The following example shows the form for the two lines you need:
<literallayout class= 'monospaced' >
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IMAGE_INSTALL = "packagegroup-core-x11-base package1 package2"
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inherit core-image
</literallayout>
</para>
<para >
By creating a custom image, a developer has total control
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over the contents of the image.
It is important to use the correct names of packages in the
<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-IMAGE_INSTALL' > IMAGE_INSTALL</ulink> </filename>
variable.
You must use the OpenEmbedded notation and not the Debian notation for the names
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(e.g. <filename > eglibc-dev</filename> instead of <filename > libc6-dev</filename> ).
</para>
<para >
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The other method for creating a custom image is to base it on an existing image.
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For example, if you want to create an image based on <filename > core-image-sato</filename>
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but add the additional package <filename > strace</filename> to the image,
copy the <filename > meta/recipes-sato/images/core-image-sato.bb</filename> to a
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new <filename > .bb</filename> and add the following line to the end of the copy:
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<literallayout class= 'monospaced' >
IMAGE_INSTALL += "strace"
</literallayout>
</para>
</section>
<section id= 'usingpoky-extend-customimage-customtasks' >
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<title > Customizing Images Using Custom Package Groups</title>
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<para >
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For complex custom images, the best approach is to create a custom package group recipe
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that is used to build the image or images.
A good example of a package group recipe is
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<filename > meta/recipes-core/packagegroups/packagegroup-core-boot.bb</filename> .
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The
<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-PACKAGES' > PACKAGES</ulink> </filename>
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variable lists the package group packages you wish to produce. <filename > inherit packagegroup</filename>
sets appropriate default values and automatically adds <filename > -dev</filename>
and <filename > -dbg</filename> complementary
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packages for every package specified in <filename > PACKAGES</filename> .
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Note that the inherit line should be towards
the top of the recipe, certainly before you set <filename > PACKAGES</filename> .
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For each package you specify in <filename > PACKAGES</filename> , you can use
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<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-RDEPENDS' > RDEPENDS</ulink> </filename>
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and
<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-RRECOMMENDS' > RRECOMMENDS</ulink> </filename>
entries to provide a list of packages the parent task package should contain.
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Following is an example:
<literallayout class= 'monospaced' >
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DESCRIPTION = "My Custom Package Groups"
inherit packagegroup
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PACKAGES = "\
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packagegroup-custom-apps \
packagegroup-custom-tools \
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"
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RDEPENDS_packagegroup-custom-apps = "\
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dropbear \
portmap \
psplash"
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RDEPENDS_packagegroup-custom-tools = "\
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oprofile \
oprofileui-server \
lttng-control \
lttng-viewer"
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RRECOMMENDS_packagegroup-custom-tools = "\
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kernel-module-oprofile"
</literallayout>
</para>
<para >
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In the previous example, two package group packages are created with their dependencies and their
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recommended package dependencies listed: <filename > packagegroup-custom-apps</filename> , and
<filename > packagegroup-custom-tools</filename> .
To build an image using these package group packages, you need to add
<filename > packagegroup-custom-apps</filename> and/or
<filename > packagegroup-custom-tools</filename> to
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<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-IMAGE_INSTALL' > IMAGE_INSTALL</ulink> </filename> .
For other forms of image dependencies see the other areas of this section.
</para>
</section>
<section id= 'usingpoky-extend-customimage-imagefeatures' >
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<title > Customizing Images Using Custom <filename > IMAGE_FEATURES</filename> and
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<filename > EXTRA_IMAGE_FEATURES</filename> </title>
<para >
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Ultimately users might want to add extra image features to the set by using the
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<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-IMAGE_FEATURES' > IMAGE_FEATURES</ulink> </filename>
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variable.
To create these features, the best reference is
<filename > meta/classes/core-image.bbclass</filename> , which shows how this is
achieved.
In summary, the file looks at the contents of the
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<filename > IMAGE_FEATURES</filename>
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variable and then maps that into a set of tasks or packages.
Based on this information, the
<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-IMAGE_INSTALL' > IMAGE_INSTALL</ulink> </filename>
variable is generated automatically.
Users can add extra features by extending the class or creating a custom class for use
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with specialized image <filename > .bb</filename> files.
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You can also add more features by configuring the
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<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-EXTRA_IMAGE_FEATURES' > EXTRA_IMAGE_FEATURES</ulink> </filename>
2012-10-22 16:59:12 +00:00
variable in the <filename > local.conf</filename> file found in the Source Directory
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located in the Build Directory.
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</para>
<para >
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The Yocto Project ships with two SSH servers you can use in your images:
Dropbear and OpenSSH.
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Dropbear is a minimal SSH server appropriate for resource-constrained environments,
while OpenSSH is a well-known standard SSH server implementation.
By default, the <filename > core-image-sato</filename> image is configured to use Dropbear.
The <filename > core-image-basic</filename> and <filename > core-image-lsb</filename>
images both include OpenSSH.
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The <filename > core-image-minimal</filename> image does not contain an SSH server.
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To change these defaults, edit the <filename > IMAGE_FEATURES</filename> variable
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so that it sets the image you are working with to include
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<filename > ssh-server-dropbear</filename> or <filename > ssh-server-openssh</filename> .
</para>
</section>
<section id= 'usingpoky-extend-customimage-localconf' >
<title > Customizing Images Using <filename > local.conf</filename> </title>
<para >
It is possible to customize image contents by using variables from your
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local configuration in your <filename > conf/local.conf</filename> file.
Because it is limited to local use, this method generally only allows you to
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add packages and is not as flexible as creating your own customized image.
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When you add packages using local variables this way, you need to realize that
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these variable changes affect all images at the same time and might not be
what you require.
</para>
2012-03-29 21:54:55 +00:00
<para >
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The simplest way to add extra packages to all images is by using the
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<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-IMAGE_INSTALL' > IMAGE_INSTALL</ulink> </filename>
variable with the <filename > _append</filename> operator:
<literallayout class= 'monospaced' >
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IMAGE_INSTALL_append = " strace"
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</literallayout>
Use of the syntax is important.
Specifically, the space between the quote and the package name, which is
<filename > strace</filename> in this example.
This space is required since the <filename > _append</filename>
operator does not add the space.
</para>
<para >
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Furthermore, you must use <filename > _append</filename> instead of the <filename > +=</filename>
operator if you want to avoid ordering issues.
The reason for this is because doing so unconditionally appends to the variable and
avoids ordering problems due to the variable being set in image recipes and
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<filename > .bbclass</filename> files with operators like <filename > ?=</filename> .
Using <filename > _append</filename> ensures the operation takes affect.
</para>
<para >
As shown in its simplest use, <filename > IMAGE_INSTALL_append</filename> affects
all images.
It is possible to extend the syntax so that the variable applies to a specific image only.
Here is an example:
<literallayout class= 'monospaced' >
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IMAGE_INSTALL_append_pn-core-image-minimal = " strace"
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</literallayout>
This example adds <filename > strace</filename> to <filename > core-image-minimal</filename>
only.
</para>
<para >
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You can add packages using a similar approach through the
<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-CORE_IMAGE_EXTRA_INSTALL' > CORE_IMAGE_EXTRA_INSTALL</ulink> </filename>
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variable.
If you use this variable, only <filename > core-image-*</filename> images are affected.
</para>
2012-03-29 19:31:41 +00:00
</section>
</section>
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<section id= 'usingpoky-extend-addpkg' >
<title > Adding a Package</title>
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2008-02-26 11:31:34 +00:00
<para >
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To add a package you need to write a recipe for it.
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Writing a recipe means creating a <filename > .bb</filename> file that sets some
variables.
For information on variables that are useful for recipes and for information about recipe naming
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issues, see the
"<ulink url= '&YOCTO_DOCS_REF_URL;#ref-varlocality-recipe-required' > Required</ulink> "
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section of the Yocto Project Reference Manual.
2008-02-26 11:31:34 +00:00
</para>
2011-08-18 22:26:48 +00:00
2008-02-26 11:31:34 +00:00
<para >
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Before writing a recipe from scratch, it is often useful to check
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whether someone else has written one already.
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OpenEmbedded is a good place to look as it has a wider scope and range of packages.
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Because the Yocto Project aims to be compatible with OpenEmbedded, most recipes
2012-07-02 16:59:11 +00:00
you find there should work for you.
2009-04-28 07:24:47 +00:00
</para>
2011-08-18 22:26:48 +00:00
2009-04-28 07:24:47 +00:00
<para >
For new packages, the simplest way to add a recipe is to base it on a similar
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pre-existing recipe.
The sections that follow provide some examples that show how to add standard
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types of packages.
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</para>
<section id= 'usingpoky-extend-addpkg-singlec' >
<title > Single .c File Package (Hello World!)</title>
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2008-02-26 11:31:34 +00:00
<para >
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Building an application from a single file that is stored locally (e.g. under
<filename > files/</filename> ) requires a recipe that has the file listed in
the
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<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-SRC_URI' > SRC_URI</ulink> </filename>
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variable.
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Additionally, you need to manually write the <filename > do_compile</filename> and
<filename > do_install</filename> tasks.
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The <filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-S' > S</ulink> </filename>
variable defines the
directory containing the source code, which is set to
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<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-WORKDIR' >
2012-02-06 17:39:17 +00:00
WORKDIR</ulink> </filename> in this case - the directory BitBake uses for the build.
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<literallayout class= 'monospaced' >
DESCRIPTION = "Simple helloworld application"
SECTION = "examples"
LICENSE = "MIT"
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LIC_FILES_CHKSUM = "file://${COMMON_LICENSE_DIR}/MIT;md5=0835ade698e0bcf8506ecda2f7b4f302"
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PR = "r0"
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SRC_URI = "file://helloworld.c"
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2011-08-18 22:26:48 +00:00
S = "${WORKDIR}"
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2011-08-18 22:26:48 +00:00
do_compile() {
${CC} helloworld.c -o helloworld
}
do_install() {
install -d ${D}${bindir}
install -m 0755 helloworld ${D}${bindir}
}
</literallayout>
</para>
2008-02-26 11:31:34 +00:00
<para >
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By default, the <filename > helloworld</filename> , <filename > helloworld-dbg</filename> ,
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and <filename > helloworld-dev</filename> packages are built.
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For information on how to customize the packaging process, see the
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"<link linkend= 'splitting-an-application-into-multiple-packages' > Splitting an Application
into Multiple Packages</link> " section.
2008-02-26 11:31:34 +00:00
</para>
</section>
<section id= 'usingpoky-extend-addpkg-autotools' >
<title > Autotooled Package</title>
<para >
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Applications that use Autotools such as <filename > autoconf</filename> and
<filename > automake</filename> require a recipe that has a source archive listed in
<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-SRC_URI' > SRC_URI</ulink> </filename> and
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also inherits Autotools, which instructs BitBake to use the
2010-11-11 21:40:30 +00:00
<filename > autotools.bbclass</filename> file, which contains the definitions of all the steps
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needed to build an Autotool-based application.
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The result of the build is automatically packaged.
And, if the application uses NLS for localization, packages with local information are
generated (one package per language).
2011-05-13 17:27:40 +00:00
Following is one example: (<filename > hello_2.3.bb</filename> )
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<literallayout class= 'monospaced' >
DESCRIPTION = "GNU Helloworld application"
SECTION = "examples"
LICENSE = "GPLv2+"
LIC_FILES_CHKSUM = "file://COPYING;md5=751419260aa954499f7abaabaa882bbe"
PR = "r0"
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SRC_URI = "${GNU_MIRROR}/hello/hello-${PV}.tar.gz"
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2011-08-18 22:26:48 +00:00
inherit autotools gettext
</literallayout>
2010-09-09 09:00:31 +00:00
</para>
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<para >
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The variable
<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-LIC_FILES_CHKSUM' > LIC_FILES_CHKSUM</ulink> </filename>
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is used to track source license changes as described in the
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"<ulink url= '&YOCTO_DOCS_REF_URL;#usingpoky-configuring-LIC_FILES_CHKSUM' > Track License Changes</ulink> " section.
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You can quickly create Autotool-based recipes in a manner similar to the previous example.
</para>
2008-02-26 11:31:34 +00:00
</section>
2010-11-04 21:12:46 +00:00
2008-02-26 11:31:34 +00:00
<section id= 'usingpoky-extend-addpkg-makefile' >
<title > Makefile-Based Package</title>
2011-08-18 22:26:48 +00:00
2008-02-26 11:31:34 +00:00
<para >
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Applications that use GNU <filename > make</filename> also require a recipe that has
2012-12-07 23:23:56 +00:00
the source archive listed in
<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-SRC_URI' > SRC_URI</ulink> </filename> .
You do not need to add a <filename > do_compile</filename> step since by default BitBake
starts the <filename > make</filename> command to compile the application.
If you need additional <filename > make</filename> options you should store them in the
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<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-EXTRA_OEMAKE' > EXTRA_OEMAKE</ulink> </filename>
variable.
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BitBake passes these options into the <filename > make</filename> GNU invocation.
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Note that a <filename > do_install</filename> task is still required.
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Otherwise, BitBake runs an empty <filename > do_install</filename> task by default.
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</para>
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2008-02-26 11:31:34 +00:00
<para >
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Some applications might require extra parameters to be passed to the compiler.
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For example, the application might need an additional header path.
You can accomplish this by adding to the
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<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-CFLAGS' > CFLAGS</ulink> </filename> variable.
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The following example shows this:
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<literallayout class= 'monospaced' >
CFLAGS_prepend = "-I ${S}/include "
</literallayout>
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</para>
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2010-09-09 09:00:31 +00:00
<para >
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In the following example, <filename > mtd-utils</filename> is a makefile-based package:
<literallayout class= 'monospaced' >
DESCRIPTION = "Tools for managing memory technology devices."
SECTION = "base"
DEPENDS = "zlib lzo e2fsprogs util-linux"
HOMEPAGE = "http://www.linux-mtd.infradead.org/"
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LICENSE = "GPLv2+"
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LIC_FILES_CHKSUM = "file://COPYING;md5=0636e73ff0215e8d672dc4c32c317bb3 \
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file://include/common.h;beginline=1;endline=17;md5=ba05b07912a44ea2bf81ce409380049c"
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SRC_URI = "git://git.infradead.org/mtd-utils.git;protocol=git;tag=995cfe51b0a3cf32f381c140bf72b21bf91cef1b \
file://add-exclusion-to-mkfs-jffs2-git-2.patch"
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S = "${WORKDIR}/git/"
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PR = "r1"
EXTRA_OEMAKE = "'CC=${CC}' 'RANLIB=${RANLIB}' 'AR=${AR}' \
'CFLAGS=${CFLAGS} -I${S}/include -DWITHOUT_XATTR' 'BUILDDIR=${S}'"
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do_install () {
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oe_runmake install DESTDIR=${D} SBINDIR=${sbindir} MANDIR=${mandir} \
INCLUDEDIR=${includedir}
install -d ${D}${includedir}/mtd/
for f in ${S}/include/mtd/*.h; do
install -m 0644 $f ${D}${includedir}/mtd/
done
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}
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PARALLEL_MAKE = ""
BBCLASSEXTEND = "native"
</literallayout>
</para>
<para >
If your sources are available as a tarball instead of a Git repository, you
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will need to provide the URL to the tarball as well as an
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<filename > md5</filename> or <filename > sha256</filename> sum of
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the download.
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Here is an example:
<literallayout class= 'monospaced' >
SRC_URI="ftp://ftp.infradead.org/pub/mtd-utils/mtd-utils-1.4.9.tar.bz2"
SRC_URI[md5sum]="82b8e714b90674896570968f70ca778b"
</literallayout>
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You can generate the <filename > md5</filename> or <filename > sha256</filename> sums
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by using the <filename > md5sum</filename> or <filename > sha256sum</filename> commands
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with the target file as the only argument.
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Here is an example:
<literallayout class= 'monospaced' >
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$ md5sum mtd-utils-1.4.9.tar.bz2
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82b8e714b90674896570968f70ca778b mtd-utils-1.4.9.tar.bz2
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</literallayout>
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</para>
</section>
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2011-09-26 17:13:56 +00:00
<section id= 'splitting-an-application-into-multiple-packages' >
<title > Splitting an Application into Multiple Packages</title>
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<para >
You can use the variables
<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-PACKAGES' > PACKAGES</ulink> </filename> and
<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-FILES' > FILES</ulink> </filename>
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to split an application into multiple packages.
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</para>
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2008-02-26 11:31:34 +00:00
<para >
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Following is an example that uses the <filename > libXpm</filename> recipe.
By default, this recipe generates a single package that contains the library along
with a few binaries.
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You can modify the recipe to split the binaries into separate packages:
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<literallayout class= 'monospaced' >
require xorg-lib-common.inc
DESCRIPTION = "X11 Pixmap library"
LICENSE = "X-BSD"
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LIC_FILES_CHKSUM = "file://COPYING;md5=3e07763d16963c3af12db271a31abaa5"
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DEPENDS += "libxext libsm libxt"
PR = "r3"
PE = "1"
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XORG_PN = "libXpm"
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PACKAGES =+ "sxpm cxpm"
FILES_cxpm = "${bindir}/cxpm"
FILES_sxpm = "${bindir}/sxpm"
</literallayout>
</para>
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<para >
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In the previous example, we want to ship the <filename > sxpm</filename>
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and <filename > cxpm</filename> binaries in separate packages.
Since <filename > bindir</filename> would be packaged into the main
<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-PN' > PN</ulink> </filename>
package by default, we prepend the
2012-03-09 19:40:39 +00:00
<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-PACKAGES' > PACKAGES</ulink>
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</filename> variable so additional package names are added to the start of list.
This results in the extra
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<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-FILES' > FILES</ulink> _*</filename>
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variables then containing information that define which files and
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directories go into which packages.
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Files included by earlier packages are skipped by latter packages.
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Thus, the main
<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-PN' > PN</ulink> </filename> package
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does not include the above listed files.
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</para>
</section>
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<section id= 'including-static-library-files' >
<title > Including Static Library Files</title>
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<para >
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If you are building a library and the library offers static linking, you can control
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which static library files (<filename > *.a</filename> files) get included in the
built library.
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</para>
<para >
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The <ulink url= '&YOCTO_DOCS_REF_URL;#var-PACKAGES' > <filename > PACKAGES</filename> </ulink>
and <ulink url= '&YOCTO_DOCS_REF_URL;#var-FILES' > <filename > FILES_*</filename> </ulink>
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variables in the
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<filename > meta/conf/bitbake.conf</filename> configuration file define how files installed
by the <filename > do_install</filename> task are packaged.
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By default, the <filename > PACKAGES</filename> variable contains
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<filename > ${PN}-staticdev</filename> , which includes all static library files.
<note >
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Previously released versions of the Yocto Project defined the static library files
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through <filename > ${PN}-dev</filename> .
</note>
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Following, is part of the BitBake configuration file.
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You can see where the static library files are defined:
<literallayout class= 'monospaced' >
PACKAGES = "${PN}-dbg ${PN} ${PN}-doc ${PN}-dev ${PN}-staticdev ${PN}-locale"
PACKAGES_DYNAMIC = "${PN}-locale-*"
FILES = ""
FILES_${PN} = "${bindir}/* ${sbindir}/* ${libexecdir}/* ${libdir}/lib*${SOLIBS} \
${sysconfdir} ${sharedstatedir} ${localstatedir} \
${base_bindir}/* ${base_sbindir}/* \
${base_libdir}/*${SOLIBS} \
${datadir}/${BPN} ${libdir}/${BPN}/* \
${datadir}/pixmaps ${datadir}/applications \
${datadir}/idl ${datadir}/omf ${datadir}/sounds \
${libdir}/bonobo/servers"
FILES_${PN}-doc = "${docdir} ${mandir} ${infodir} ${datadir}/gtk-doc \
${datadir}/gnome/help"
SECTION_${PN}-doc = "doc"
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FILES_${PN}-dev = "${includedir} ${libdir}/lib*${SOLIBSDEV} ${libdir}/*.la \
${libdir}/*.o ${libdir}/pkgconfig ${datadir}/pkgconfig \
${datadir}/aclocal ${base_libdir}/*.o"
SECTION_${PN}-dev = "devel"
ALLOW_EMPTY_${PN}-dev = "1"
RDEPENDS_${PN}-dev = "${PN} (= ${EXTENDPKGV})"
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FILES_${PN}-staticdev = "${libdir}/*.a ${base_libdir}/*.a"
SECTION_${PN}-staticdev = "devel"
RDEPENDS_${PN}-staticdev = "${PN}-dev (= ${EXTENDPKGV})"
</literallayout>
</para>
</section>
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<section id= 'usingpoky-extend-addpkg-postinstalls' >
<title > Post Install Scripts</title>
<para >
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To add a post-installation script to a package, add a <filename > pkg_postinst_PACKAGENAME()
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</filename> function to the <filename > .bb</filename> file and use
<filename > PACKAGENAME</filename> as the name of the package you want to attach to the
2010-10-28 21:29:17 +00:00
<filename > postinst</filename> script.
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Normally
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<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-PN' > PN</ulink> </filename>
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can be used, which automatically expands to <filename > PACKAGENAME</filename> .
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A post-installation function has the following structure:
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<literallayout class= 'monospaced' >
pkg_postinst_PACKAGENAME () {
#!/bin/sh -e
# Commands to carry out
}
</literallayout>
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</para>
2011-08-18 22:26:48 +00:00
2008-02-26 11:31:34 +00:00
<para >
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The script defined in the post-installation function is called when the
root filesystem is created.
If the script succeeds, the package is marked as installed.
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If the script fails, the package is marked as unpacked and the script is
executed when the image boots again.
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</para>
2011-08-18 22:26:48 +00:00
2008-02-26 11:31:34 +00:00
<para >
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Sometimes it is necessary for the execution of a post-installation
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script to be delayed until the first boot.
For example, the script might need to be executed on the device itself.
To delay script execution until boot time, use the following structure in the
2010-10-28 21:29:17 +00:00
post-installation script:
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<literallayout class= 'monospaced' >
pkg_postinst_PACKAGENAME () {
#!/bin/sh -e
if [ x"$D" = "x" ]; then
# Actions to carry out on the device go here
else
exit 1
fi
}
</literallayout>
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</para>
2011-08-18 22:26:48 +00:00
2008-02-26 11:31:34 +00:00
<para >
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The previous example delays execution until the image boots again because the
<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-D' > D</ulink> </filename>
2012-02-06 17:39:17 +00:00
variable points
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to the directory containing the image when the root filesystem is created at build time but
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is unset when executed on the first boot.
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</para>
</section>
</section>
2010-11-04 21:12:46 +00:00
<section id= "platdev-newmachine" >
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<title > Adding a New Machine</title>
2012-02-08 15:47:11 +00:00
2008-02-26 11:31:34 +00:00
<para >
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Adding a new machine to the Yocto Project is a straightforward process.
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This section provides information that gives you an idea of the changes you must make.
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The information covers adding machines similar to those the Yocto Project already supports.
Although well within the capabilities of the Yocto Project, adding a totally new architecture
might require
changes to <filename > gcc/eglibc</filename> and to the site information, which is
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beyond the scope of this manual.
2008-02-26 11:31:34 +00:00
</para>
2011-08-26 21:27:40 +00:00
<para >
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For a complete example that shows how to add a new machine,
see the
"<ulink url= '&YOCTO_DOCS_BSP_URL;#creating-a-new-bsp-layer-using-the-yocto-bsp-script' > Creating a New BSP Layer Using the yocto-bsp Script</ulink> "
2012-10-03 21:05:17 +00:00
in the Yocto Project Board Support Package (BSP) Developer's Guide.
2011-08-26 21:27:40 +00:00
</para>
2010-11-04 21:12:46 +00:00
<section id= "platdev-newmachine-conffile" >
<title > Adding the Machine Configuration File</title>
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2010-11-04 21:12:46 +00:00
<para >
To add a machine configuration you need to add a <filename > .conf</filename> file
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with details of the device being added to the <filename > conf/machine/</filename> file.
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The name of the file determines the name the OpenEmbedded build system
uses to reference the new machine.
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</para>
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2010-11-04 21:12:46 +00:00
<para >
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The most important variables to set in this file are as follows:
<itemizedlist >
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<listitem > <para > <filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-TARGET_ARCH' >
2012-02-06 17:39:17 +00:00
TARGET_ARCH</ulink> </filename> (e.g. "arm")</para> </listitem>
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<listitem > <para > <filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-PREFERRED_PROVIDER' >
2012-02-06 17:39:17 +00:00
PREFERRED_PROVIDER</ulink> </filename> _virtual/kernel (see below)</para> </listitem>
2012-03-09 19:40:39 +00:00
<listitem > <para > <filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-MACHINE_FEATURES' >
2012-04-23 19:22:37 +00:00
MACHINE_FEATURES</ulink> </filename> (e.g. "apm screen wifi")</para> </listitem>
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</itemizedlist>
</para>
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<para >
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You might also need these variables:
<itemizedlist >
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<listitem > <para > <filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-SERIAL_CONSOLE' >
2012-02-06 17:39:17 +00:00
SERIAL_CONSOLE</ulink> </filename> (e.g. "115200 ttyS0")</para> </listitem>
2012-03-09 19:40:39 +00:00
<listitem > <para > <filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-KERNEL_IMAGETYPE' >
2012-02-06 17:39:17 +00:00
KERNEL_IMAGETYPE</ulink> </filename> (e.g. "zImage")</para> </listitem>
2012-03-09 19:40:39 +00:00
<listitem > <para > <filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-IMAGE_FSTYPES' >
2012-02-06 17:39:17 +00:00
IMAGE_FSTYPES</ulink> </filename> (e.g. "tar.gz jffs2")</para> </listitem>
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</itemizedlist>
</para>
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<para >
You can find full details on these variables in the reference section.
You can leverage many existing machine <filename > .conf</filename> files from
2010-11-04 21:12:46 +00:00
<filename > meta/conf/machine/</filename> .
</para>
</section>
<section id= "platdev-newmachine-kernel" >
<title > Adding a Kernel for the Machine</title>
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2010-11-04 21:12:46 +00:00
<para >
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The OpenEmbedded build system needs to be able to build a kernel for the machine.
You need to either create a new kernel recipe for this machine, or extend an
existing recipe.
You can find several kernel examples in the
2012-10-22 16:59:12 +00:00
Source Directory at <filename > meta/recipes-kernel/linux</filename>
2012-07-02 16:59:11 +00:00
that you can use as references.
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</para>
2011-08-18 22:26:48 +00:00
2010-11-04 21:12:46 +00:00
<para >
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If you are creating a new recipe, normal recipe-writing rules apply for setting
up a
<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-SRC_URI' > SRC_URI</ulink> </filename> .
Thus, you need to specify any necessary patches and set
<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-S' > S</ulink> </filename> to point at the source code.
You need to create a <filename > configure</filename> task that configures the
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unpacked kernel with a defconfig.
You can do this by using a <filename > make defconfig</filename> command or,
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more commonly, by copying in a suitable <filename > defconfig</filename> file and and then running
<filename > make oldconfig</filename> .
By making use of <filename > inherit kernel</filename> and potentially some of the
<filename > linux-*.inc</filename> files, most other functionality is
2010-11-04 21:12:46 +00:00
centralized and the the defaults of the class normally work well.
</para>
2011-08-18 22:26:48 +00:00
2010-11-04 21:12:46 +00:00
<para >
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If you are extending an existing kernel, it is usually a matter of adding a
2011-08-18 22:26:48 +00:00
suitable defconfig file.
The file needs to be added into a location similar to defconfig files
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used for other machines in a given kernel.
A possible way to do this is by listing the file in the
<filename > SRC_URI</filename> and adding the machine to the expression in
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<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-COMPATIBLE_MACHINE' > COMPATIBLE_MACHINE</ulink> </filename> :
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<literallayout class= 'monospaced' >
COMPATIBLE_MACHINE = '(qemux86|qemumips)'
</literallayout>
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</para>
</section>
2008-02-26 11:31:34 +00:00
2010-11-04 21:12:46 +00:00
<section id= "platdev-newmachine-formfactor" >
<title > Adding a Formfactor Configuration File</title>
2011-08-18 22:26:48 +00:00
2010-11-04 21:12:46 +00:00
<para >
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A formfactor configuration file provides information about the
target hardware for which the image is being built and information that
the build system cannot obtain from other sources such as the kernel.
Some examples of information contained in a formfactor configuration file include
framebuffer orientation, whether or not the system has a keyboard,
the positioning of the keyboard in relation to the screen, and
2010-11-11 21:40:30 +00:00
the screen resolution.
2010-11-04 21:12:46 +00:00
</para>
2011-08-18 22:26:48 +00:00
2010-11-04 21:12:46 +00:00
<para >
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The build system uses reasonable defaults in most cases, but if customization is
necessary you need to create a <filename > machconfig</filename> file
2012-07-02 16:59:11 +00:00
in the <filename > meta/recipes-bsp/formfactor/files</filename>
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directory.
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This directory contains directories for specific machines such as
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<filename > qemuarm</filename> and <filename > qemux86</filename> .
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For information about the settings available and the defaults, see the
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<filename > meta/recipes-bsp/formfactor/files/config</filename> file found in the
2012-12-07 23:23:56 +00:00
same area.
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Following is an example for qemuarm:
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<literallayout class= 'monospaced' >
HAVE_TOUCHSCREEN=1
HAVE_KEYBOARD=1
DISPLAY_CAN_ROTATE=0
DISPLAY_ORIENTATION=0
#DISPLAY_WIDTH_PIXELS=640
#DISPLAY_HEIGHT_PIXELS=480
#DISPLAY_BPP=16
DISPLAY_DPI=150
DISPLAY_SUBPIXEL_ORDER=vrgb
</literallayout>
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</para>
</section>
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</section>
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<section id= "building-multiple-architecture-libraries-into-one-image" >
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<title > Combining Multiple Versions of Library Files into One Image</title>
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<para >
The build system offers the ability to build libraries with different
target optimizations or architecture formats and combine these together
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into one system image.
You can link different binaries in the image
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against the different libraries as needed for specific use cases.
This feature is called "Multilib."
</para>
<para >
An example would be where you have most of a system compiled in 32-bit
mode using 32-bit libraries, but you have something large, like a database
engine, that needs to be a 64-bit application and use 64-bit libraries.
Multilib allows you to get the best of both 32-bit and 64-bit libraries.
</para>
<para >
While the Multilib feature is most commonly used for 32 and 64-bit differences,
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the approach the build system uses facilitates different target optimizations.
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You could compile some binaries to use one set of libraries and other binaries
to use other different sets of libraries.
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The libraries could differ in architecture, compiler options, or other
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optimizations.
</para>
<para >
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This section overviews the Multilib process only.
For more details on how to implement Multilib, see the
<ulink url= '&YOCTO_WIKI_URL;/wiki/Multilib' > Multilib</ulink> wiki
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page.
</para>
<section id= 'preparing-to-use-multilib' >
<title > Preparing to use Multilib</title>
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<para >
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User-specific requirements drive the Multilib feature,
Consequently, there is no one "out-of-the-box" configuration that likely
exists to meet your needs.
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</para>
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2010-11-04 21:12:46 +00:00
<para >
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In order to enable Multilib, you first need to ensure your recipe is
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extended to support multiple libraries.
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Many standard recipes are already extended and support multiple libraries.
You can check in the <filename > meta/conf/multilib.conf</filename>
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configuration file in the Source Directory to see how this is
done using the
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<ulink url= '&YOCTO_DOCS_REF_URL;#var-BBCLASSEXTEND' > <filename > BBCLASSEXTEND</filename> </ulink>
variable.
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Eventually, all recipes will be covered and this list will be unneeded.
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</para>
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2010-06-08 16:18:29 +00:00
<para >
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For the most part, the Multilib class extension works automatically to
extend the package name from <filename > ${PN}</filename> to
<filename > ${MLPREFIX}${PN}</filename> , where <filename > MLPREFIX</filename>
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is the particular multilib (e.g. "lib32-" or "lib64-").
Standard variables such as
<ulink url= '&YOCTO_DOCS_REF_URL;#var-DEPENDS' > <filename > DEPENDS</filename> </ulink> ,
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<ulink url= '&YOCTO_DOCS_REF_URL;#var-RDEPENDS' > <filename > RDEPENDS</filename> </ulink> ,
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<filename > RPROVIDES</filename> ,
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<ulink url= '&YOCTO_DOCS_REF_URL;#var-RRECOMMENDS' > <filename > RRECOMMENDS</filename> </ulink> ,
<ulink url= '&YOCTO_DOCS_REF_URL;#var-PACKAGES' > <filename > PACKAGES</filename> </ulink> ,
and <filename > PACKAGES_DYNAMIC</filename> are automatically extended by the system.
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If you are extending any manual code in the recipe, you can use the
<filename > ${MLPREFIX}</filename> variable to ensure those names are extended
correctly.
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This automatic extension code resides in <filename > multilib.bbclass</filename> .
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</para>
</section>
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<section id= 'using-multilib' >
<title > Using Multilib</title>
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2010-11-04 21:12:46 +00:00
<para >
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After you have set up the recipes, you need to define the actual
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combination of multiple libraries you want to build.
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You accomplish this through your <filename > local.conf</filename>
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configuration file in the
<link linkend= 'build-directory' > Build Directory</link> .
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An example configuration would be as follows:
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<literallayout class= 'monospaced' >
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MACHINE = "qemux86-64"
require conf/multilib.conf
MULTILIBS = "multilib:lib32"
DEFAULTTUNE_virtclass-multilib-lib32 = "x86"
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IMAGE_INSTALL = "lib32-connman"
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</literallayout>
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This example enables an
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additional library named <filename > lib32</filename> alongside the
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normal target packages.
When combining these "lib32" alternatives, the example uses "x86" for tuning.
For information on this particular tuning, see
<filename > meta/conf/machine/include/ia32/arch-ia32.inc</filename> .
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</para>
2010-09-09 09:00:31 +00:00
2008-02-26 11:31:34 +00:00
<para >
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The example then includes <filename > lib32-connman</filename>
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in all the images, which illustrates one method of including a
multiple library dependency.
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You can use a normal image build to include this dependency,
for example:
<literallayout class= 'monospaced' >
$ bitbake core-image-sato
</literallayout>
You can also build Multilib packages specifically with a command like this:
<literallayout class= 'monospaced' >
$ bitbake lib32-connman
</literallayout>
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</para>
</section>
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<section id= 'additional-implementation-details' >
<title > Additional Implementation Details</title>
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2008-02-26 11:31:34 +00:00
<para >
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Different packaging systems have different levels of native Multilib
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support.
For the RPM Package Management System, the following implementation details
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exist:
<itemizedlist >
<listitem > <para > A unique architecture is defined for the Multilib packages,
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along with creating a unique deploy folder under
<filename > tmp/deploy/rpm</filename> in the
<link linkend= 'build-directory' > Build Directory</link> .
For example, consider <filename > lib32</filename> in a
<filename > qemux86-64</filename> image.
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The possible architectures in the system are "all", "qemux86_64",
"lib32_qemux86_64", and "lib32_x86".</para> </listitem>
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<listitem > <para > The <filename > ${MLPREFIX}</filename> variable is stripped from
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<filename > ${PN}</filename> during RPM packaging.
The naming for a normal RPM package and a Multilib RPM package in a
<filename > qemux86-64</filename> system resolves to something similar to
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<filename > bash-4.1-r2.x86_64.rpm</filename> and
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<filename > bash-4.1.r2.lib32_x86.rpm</filename> , respectively.
</para> </listitem>
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<listitem > <para > When installing a Multilib image, the RPM backend first
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installs the base image and then installs the Multilib libraries.
</para> </listitem>
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<listitem > <para > The build system relies on RPM to resolve the identical files in the
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two (or more) Multilib packages.</para> </listitem>
</itemizedlist>
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</para>
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2010-11-15 16:27:07 +00:00
<para >
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For the IPK Package Management System, the following implementation details exist:
<itemizedlist >
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<listitem > <para > The <filename > ${MLPREFIX}</filename> is not stripped from
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<filename > ${PN}</filename> during IPK packaging.
The naming for a normal RPM package and a Multilib IPK package in a
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<filename > qemux86-64</filename> system resolves to something like
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<filename > bash_4.1-r2.x86_64.ipk</filename> and
<filename > lib32-bash_4.1-rw_x86.ipk</filename> , respectively.
</para> </listitem>
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<listitem > <para > The IPK deploy folder is not modified with
<filename > ${MLPREFIX}</filename> because packages with and without
the Multilib feature can exist in the same folder due to the
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<filename > ${PN}</filename> differences.</para> </listitem>
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<listitem > <para > IPK defines a sanity check for Multilib installation
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using certain rules for file comparison, overridden, etc.
</para> </listitem>
</itemizedlist>
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</para>
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</section>
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</section>
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<section id= 'configuring-the-kernel' >
<title > Configuring the Kernel</title>
<para >
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Configuring the Yocto Project kernel consists of making sure the <filename > .config</filename>
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file has all the right information in it for the image you are building.
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You can use the <filename > menuconfig</filename> tool and configuration fragments to
make sure your <filename > .config</filename> file is just how you need it.
This section describes how to use <filename > menuconfig</filename> , create and use
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configuration fragments, and how to interactively tweak your <filename > .config</filename>
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file to create the leanest kernel configuration file possible.
</para>
<para >
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For more information on kernel configuration, see the
"<ulink url= '&YOCTO_DOCS_KERNEL_DEV_URL;#changing-the-configuration' > Changing the Configuration</ulink> "
section in the Yocto Project Linux Kernel Development Manual.
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</para>
<section id= 'using-menuconfig' >
<title > Using <filename > menuconfig</filename> </title>
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<para >
The easiest way to define kernel configurations is to set them through the
<filename > menuconfig</filename> tool.
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This tool provides an interactive method with which
to set kernel configurations.
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For general information on <filename > menuconfig</filename> , see
<ulink url= 'http://en.wikipedia.org/wiki/Menuconfig' > </ulink> .
</para>
<para >
To use the <filename > menuconfig</filename> tool in the Yocto Project development
environment, you must build the tool using BitBake.
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Thus, the environment must be set up using the <filename > &OE_INIT_FILE; </filename>
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script found in the
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<link linkend= 'build-directory' > Build Directory</link> .
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The following commands build and invoke <filename > menuconfig</filename> assuming the
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Source Directory top-level folder is <filename > ~/poky</filename> :
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<literallayout class= 'monospaced' >
$ cd ~/poky
$ source oe-init-build-env
$ bitbake linux-yocto -c menuconfig
</literallayout>
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Once <filename > menuconfig</filename> comes up, its standard interface allows you to
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interactively examine and configure all the kernel configuration parameters.
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After making your changes, simply exit the tool and save your changes to
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create an updated version of the <filename > .config</filename> configuration file.
</para>
<para >
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Consider an example that configures the <filename > linux-yocto-3.4</filename>
kernel.
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The OpenEmbedded build system recognizes this kernel as
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<filename > linux-yocto</filename> .
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Thus, the following commands from the shell in which you previously sourced the
environment initialization script cleans the shared state cache and the
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<ulink url= '&YOCTO_DOCS_REF_URL;#var-WORKDIR' > <filename > WORKDIR</filename> </ulink>
directory and then builds and launches <filename > menuconfig</filename> :
<literallayout class= 'monospaced' >
$ bitbake linux-yocto -c menuconfig
</literallayout>
</para>
<para >
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Once <filename > menuconfig</filename> launches, you use the interface
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to navigate through the selections to find the configuration settings in
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which you are interested.
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For example, consider the <filename > CONFIG_SMP</filename> configuration setting.
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You can find it at <filename > Processor Type and Features</filename> under
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the configuration selection <filename > Symmetric Multi-processing Support</filename> .
After highlighting the selection, you can use the arrow keys to select or deselect
the setting.
When you are finished with all your selections, exit out and save them.
</para>
<para >
Saving the selections updates the <filename > .config</filename> configuration file.
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This is the file that the OpenEmbedded build system uses to configure the
kernel during the build.
You can find and examine this file in the Build Directory in
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<filename > tmp/work/</filename> .
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The actual <filename > .config</filename> is located in the area where the
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specific kernel is built.
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For example, if you were building a Linux Yocto kernel based on the
Linux 3.4 kernel and you were building a QEMU image targeted for
<filename > x86</filename> architecture, the
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<filename > .config</filename> file would be located here:
<literallayout class= 'monospaced' >
~/poky/build/tmp/work/qemux86-poky-linux/linux-yocto-3.4.11+git1+84f...
...656ed30-r1/linux-qemux86-standard-build
</literallayout>
<note >
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The previous example directory is artificially split and many of the characters
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in the actual filename are omitted in order to make it more readable.
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Also, depending on the kernel you are using, the exact pathname
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for <filename > linux-yocto-3.4...</filename> might differ.
</note>
</para>
<para >
Within the <filename > .config</filename> file, you can see the kernel settings.
For example, the following entry shows that symmetric multi-processor support
is not set:
<literallayout class= 'monospaced' >
# CONFIG_SMP is not set
</literallayout>
</para>
<para >
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A good method to isolate changed configurations is to use a combination of the
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<filename > menuconfig</filename> tool and simple shell commands.
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Before changing configurations with <filename > menuconfig</filename> , copy the
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existing <filename > .config</filename> and rename it to something else,
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use <filename > menuconfig</filename> to make
as many changes an you want and save them, then compare the renamed configuration
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file against the newly created file.
You can use the resulting differences as your base to create configuration fragments
to permanently save in your kernel layer.
<note >
Be sure to make a copy of the <filename > .config</filename> and don't just
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rename it.
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The build system needs an existing <filename > .config</filename>
from which to work.
</note>
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</para>
</section>
<section id= 'creating-config-fragments' >
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<title > Creating Configuration Fragments</title>
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<para >
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Configuration fragments are simply kernel options that appear in a file
placed where the OpenEmbedded build system can find and apply them.
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Syntactically, the configuration statement is identical to what would appear
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in the <filename > .config</filename> file, which is in the
<link linkend= 'build-directory' > Build Directory</link> in
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<filename > tmp/work/< arch> -poky-linux/linux-yocto-< release-specific-string> /linux-< arch> -< build-type> </filename> .
</para>
<para >
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It is simple to create a configuration fragment.
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For example, issuing the following from the shell creates a configuration fragment
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file named <filename > my_smp.cfg</filename> that enables multi-processor support
within the kernel:
<literallayout class= 'monospaced' >
$ echo "CONFIG_SMP=y" >> my_smp.cfg
</literallayout>
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<note >
All configuration files must use the <filename > .cfg</filename> extension in order
for the OpenEmbedded build system to recognize them as a configuration fragment.
</note>
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</para>
<para >
Where do you put your configuration files?
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You can place these configuration files in the same area pointed to by
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<filename > SRC_URI</filename> .
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The OpenEmbedded build system will pick up the configuration and add it to the
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kernel's configuration.
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For example, suppose you had a set of configuration options in a file called
<filename > myconfig.cfg</filename> .
If you put that file inside a directory named <filename > /linux-yocto</filename>
that resides in the same directory as the kernel's append file and then add
a <filename > SRC_URI</filename> statement such as the following to the kernel's append file,
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those configuration options will be picked up and applied when the kernel is built.
<literallayout class= 'monospaced' >
SRC_URI += "file://myconfig.cfg"
</literallayout>
</para>
<para >
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As mentioned earlier, you can group related configurations into multiple files and
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name them all in the <filename > SRC_URI</filename> statement as well.
For example, you could group separate configurations specifically for Ethernet and graphics
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into their own files and add those by using a <filename > SRC_URI</filename> statement like the
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following in your append file:
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<literallayout class= 'monospaced' >
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SRC_URI += "file://myconfig.cfg \
file://eth.cfg \
file://gfx.cfg"
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</literallayout>
</para>
</section>
<section id= 'fine-tuning-the-kernel-configuration-file' >
<title > Fine-tuning the Kernel Configuration File</title>
<para >
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You can make sure the <filename > .config</filename> is as lean or efficient as
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possible by reading the output of the kernel configuration fragment audit,
noting any issues, making changes to correct the issues, and then repeating.
</para>
<para >
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As part of the kernel build process, the
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<filename > kernel_configcheck</filename> task runs.
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This task validates the kernel configuration by checking the final
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<filename > .config</filename> file against the input files.
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During the check, the task produces warning messages for the following
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issues:
<itemizedlist >
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<listitem > <para > Requested options that did not make the final
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<filename > .config</filename> file.</para> </listitem>
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<listitem > <para > Configuration items that appear twice in the same
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configuration fragment.</para> </listitem>
<listitem > <para > Configuration items tagged as 'required' were overridden.
</para> </listitem>
<listitem > <para > A board overrides a non-board specific option.</para> </listitem>
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<listitem > <para > Listed options not valid for the kernel being processed.
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In other words, the option does not appear anywhere.</para> </listitem>
</itemizedlist>
<note >
The <filename > kernel_configcheck</filename> task can also optionally report
if an option is overridden during processing.
</note>
</para>
<para >
For each output warning, a message points to the file
that contains a list of the options and a pointer to the config
fragment that defines them.
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Collectively, the files are the key to streamlining the configuration.
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</para>
<para >
To streamline the configuration, do the following:
<orderedlist >
<listitem > <para > Start with a full configuration that you know
works - it builds and boots successfully.
This configuration file will be your baseline.</para> </listitem>
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<listitem > <para > Separately run the <filename > configme</filename> and
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<filename > kernel_configcheck</filename> tasks.</para> </listitem>
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<listitem > <para > Take the resulting list of files from the
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<filename > kernel_configcheck</filename> task warnings and do the following:
<itemizedlist >
<listitem > <para > Drop values that are redefined in the fragment but do not
change the final <filename > .config</filename> file.</para> </listitem>
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<listitem > <para > Analyze and potentially drop values from the
<filename > .config</filename> file that override required
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configurations.</para> </listitem>
<listitem > <para > Analyze and potentially remove non-board specific options.
</para> </listitem>
<listitem > <para > Remove repeated and invalid options.</para> </listitem>
</itemizedlist> </para> </listitem>
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<listitem > <para > After you have worked through the output of the kernel configuration
audit, you can re-run the <filename > configme</filename>
and <filename > kernel_configcheck</filename> tasks to see the results of your
changes.
If you have more issues, you can deal with them as described in the
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previous step.</para> </listitem>
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</orderedlist>
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</para>
<para >
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Iteratively working through steps two through four eventually yields
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a minimal, streamlined configuration file.
Once you have the best <filename > .config</filename> , you can build the Linux
Yocto kernel.
</para>
</section>
</section>
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<section id= "patching-the-kernel" >
<title > Patching the Kernel</title>
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<para >
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Patching the kernel involves changing or adding configurations to an existing kernel,
changing or adding recipes to the kernel that are needed to support specific hardware features,
or even altering the source code itself.
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<note >
You can use the <filename > yocto-kernel</filename> script
found in the <link linkend= 'source-directory' > Source Directory</link>
under <filename > scripts</filename> to manage kernel patches and configuration.
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See the "<ulink url= '&YOCTO_DOCS_BSP_URL;#managing-kernel-patches-and-config-items-with-yocto-kernel' > Managing kernel Patches and Config Items with yocto-kernel</ulink> "
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section in the Yocto Project Board Support Packages (BSP) Developer's Guide for
more information.</note>
</para>
<para >
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This example creates a simple patch by adding some QEMU emulator console
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output at boot time through <filename > printk</filename> statements in the kernel's
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<filename > calibrate.c</filename> source code file.
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Applying the patch and booting the modified image causes the added
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messages to appear on the emulator's console.
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</para>
<para >
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The example assumes a clean build exists for the <filename > qemux86</filename>
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machine in a Source Directory named <filename > poky</filename> .
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Furthermore, the <link linkend= 'build-directory' > Build Directory</link> is
<filename > build</filename> and is located in <filename > poky</filename> and
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the kernel is based on the Linux 3.4 kernel.
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For general information on how to configure the most efficient build, see the
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"<ulink url= '&YOCTO_DOCS_QS_URL;#building-image' > Building an Image</ulink> " section
in the Yocto Project Quick Start.
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</para>
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2013-01-25 20:18:23 +00:00
<para >
Also, for more information on patching the kernel, see the
"<ulink url= '&YOCTO_DOCS_KERNEL_DEV_URL;#applying-patches' > Applying Patches</ulink> "
section in the Yocto Project Linux Kernel Development Manual.
</para>
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<section id= 'create-a-layer-for-your-changes' >
<title > Create a Layer for your Changes</title>
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<para >
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The first step is to create a layer so you can isolate your changes:
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<literallayout class= 'monospaced' >
$cd ~/poky
$mkdir meta-mylayer
</literallayout>
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Creating a directory that follows the Yocto Project layer naming
conventions sets up the layer for your changes.
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The layer is where you place your configuration files, append
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files, and patch files.
To learn more about creating a layer and filling it with the
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files you need, see the "<link linkend= 'understanding-and-creating-layers' > Understanding
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and Creating Layers</link> " section.
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</para>
</section>
<section id= 'finding-the-kernel-source-code' >
<title > Finding the Kernel Source Code</title>
<para >
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Each time you build a kernel image, the kernel source code is fetched
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and unpacked into the following directory:
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<literallayout class= 'monospaced' >
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${S}/linux
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</literallayout>
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See the "<link linkend= 'finding-the-temporary-source-code' > Finding the Temporary Source Code</link> "
section and the
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<ulink url= '&YOCTO_DOCS_REF_URL;#var-S' > <filename > S</filename> </ulink> variable
for more information about where source is kept during a build.
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</para>
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<para >
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For this example, we are going to patch the
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<filename > init/calibrate.c</filename> file
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by adding some simple console <filename > printk</filename> statements that we can
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see when we boot the image using QEMU.
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</para>
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</section>
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<section id= 'creating-the-patch' >
<title > Creating the Patch</title>
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<para >
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Two methods exist by which you can create the patch:
<link linkend= 'using-a-git-workflow' > Git workflow</link> and
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<link linkend= 'using-a-quilt-workflow' > Quilt workflow</link> .
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For kernel patches, the Git workflow is more appropriate.
This section assumes the Git workflow and shows the steps specific to
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this example.
<orderedlist >
<listitem > <para > <emphasis > Change the working directory</emphasis> :
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Change to where the kernel source code is before making
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your edits to the <filename > calibrate.c</filename> file:
<literallayout class= 'monospaced' >
$ cd ~/poky/build/tmp/work/qemux86-poky-linux/linux-yocto-${PV}-${PR}/linux
</literallayout>
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Because you are working in an established Git repository,
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you must be in this directory in order to commit your changes
and create the patch file.
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<note > The <ulink url= '&YOCTO_DOCS_REF_URL;#var-PV' > <filename > PV</filename> </ulink> and
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<ulink url= '&YOCTO_DOCS_REF_URL;#var-PR' > <filename > PR</filename> </ulink> variables
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represent the version and revision for the
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<filename > linux-yocto</filename> recipe.
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The <filename > PV</filename> variable includes the Git meta and machine
hashes, which make the directory name longer than you might
expect.
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</note> </para> </listitem>
<listitem > <para > <emphasis > Edit the source file</emphasis> :
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Edit the <filename > init/calibrate.c</filename> file to have the
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following changes:
<literallayout class= 'monospaced' >
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void __cpuinit calibrate_delay(void)
{
unsigned long lpj;
static bool printed;
int this_cpu = smp_processor_id();
printk("*************************************\n");
printk("* *\n");
printk("* HELLO YOCTO KERNEL *\n");
printk("* *\n");
printk("*************************************\n");
if (per_cpu(cpu_loops_per_jiffy, this_cpu)) {
.
.
.
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</literallayout> </para> </listitem>
<listitem > <para > <emphasis > Stage and commit your changes</emphasis> :
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These Git commands list out the changed file, stage it, and then
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commit the file:
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<literallayout class= 'monospaced' >
$ git status
$ git add init/calibrate.c
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$ git commit -m "calibrate: Add printk example"
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</literallayout> </para> </listitem>
<listitem > <para > <emphasis > Generate the patch file</emphasis> :
This Git command creates the a patch file named
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<filename > 0001-calibrate-Add-printk-example.patch</filename>
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in the current directory.
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<literallayout class= 'monospaced' >
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$ git format-patch -1
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</literallayout>
</para> </listitem>
</orderedlist>
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</para>
</section>
2012-10-08 17:14:58 +00:00
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<section id= 'get-your-layer-setup-for-the-build' >
<title > Get Your Layer Setup for the Build</title>
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<para > These steps get your layer set up for the build:
<orderedlist >
<listitem > <para > <emphasis > Create additional structure</emphasis> :
Create the additional layer structure:
<literallayout class= 'monospaced' >
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$ cd ~/poky/meta-mylayer
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$ mkdir conf
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$ mkdir recipes-kernel
$ mkdir recipes-kernel/linux
$ mkdir recipes-kernel/linux/linux-yocto
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</literallayout>
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The <filename > conf</filename> directory holds your configuration files, while the
<filename > recipes-kernel</filename> directory holds your append file and
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your patch file.</para> </listitem>
<listitem > <para > <emphasis > Create the layer configuration file</emphasis> :
Move to the <filename > meta-mylayer/conf</filename> directory and create
the <filename > layer.conf</filename> file as follows:
<literallayout class= 'monospaced' >
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# We have a conf and classes directory, add to BBPATH
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BBPATH := "${BBPATH}:${LAYERDIR}"
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# We have a packages directory, add to BBFILES
BBFILES := "${BBFILES} ${LAYERDIR}/recipes-*/*/*.bb \
${LAYERDIR}/recipes-*/*/*.bbappend"
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BBFILE_COLLECTIONS += "mylayer"
BBFILE_PATTERN_mylayer := "^${LAYERDIR}/"
BBFILE_PRIORITY_mylayer = "5"
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</literallayout>
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Notice <filename > mylayer</filename> as part of the last three
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statements.</para> </listitem>
<listitem > <para > <emphasis > Create the kernel recipe append file</emphasis> :
Move to the <filename > meta-mylayer/recipes-kernel/linux</filename> directory and create
the <filename > linux-yocto_3.4.bbappend</filename> file as follows:
<literallayout class= 'monospaced' >
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FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
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SRC_URI += "file://0001-calibrate-Add-printk-example.patch"
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PRINC := "${@int(PRINC) + 1}"
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</literallayout>
The <filename > FILESEXTRAPATHS</filename> and <filename > SRC_URI</filename>
statements enable the OpenEmbedded build system to find the patch file.
</para> </listitem>
<listitem > <para > <emphasis > Put the patch file in your layer</emphasis> :
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Move the <filename > 0001-calibrate-Add-printk-example.patch</filename> file to
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the <filename > meta-mylayer/recipes-kernel/linux/linux-yocto</filename>
directory.</para> </listitem>
</orderedlist>
</para>
</section>
<section id= 'set-up-for-the-build' >
<title > Set Up for the Build</title>
<para >
Do the following to make sure the build parameters are set up for the example.
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Once you set up these build parameters, they do not have to change unless you
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change the target architecture of the machine you are building:
<itemizedlist >
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<listitem > <para > <emphasis > Build for the Correct Target Architecture:</emphasis> Your
selected <ulink url= '&YOCTO_DOCS_REF_URL;#var-MACHINE' > <filename > MACHINE</filename> </ulink>
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definition within the <filename > local.conf</filename> file in the Build Directory
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specifies the target architecture used when building the Linux kernel.
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By default, <filename > MACHINE</filename> is set to
<filename > qemux86</filename> , which specifies a 32-bit
<trademark class= 'registered' > Intel</trademark> Architecture
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target machine suitable for the QEMU emulator.</para> </listitem>
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<listitem > <para > <emphasis > Identify Your <filename > meta-mylayer</filename>
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Layer:</emphasis> The <filename > BBLAYERS</filename> variable in the
<filename > bblayers.conf</filename> file found in the
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<filename > poky/build/conf</filename> directory needs to have the path to your local
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<filename > meta-mylayer</filename> layer.
By default, the <filename > BBLAYERS</filename> variable contains paths to
<filename > meta</filename> , <filename > meta-yocto</filename> , and
<filename > meta-yocto-bsp</filename> in the
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<filename > poky</filename> Git repository.
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Add the path to your <filename > meta-mylayer</filename> location:
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<literallayout class= 'monospaced' >
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BBLAYERS ?= " \
$HOME/poky/meta \
$HOME/poky/meta-yocto \
$HOME/poky/meta-yocto-bsp \
$HOME/poky/meta-mylayer \
"
BBLAYERS_NON_REMOVABLE ?= " \
$HOME/poky/meta \
$HOME/poky/meta-yocto \
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"
</literallayout> </para> </listitem>
</itemizedlist>
</para>
</section>
2012-10-08 17:14:58 +00:00
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<section id= 'build-and-booting-the-modified-qemu-kernel-image' >
<title > Build and Booting the Modified QEMU Kernel Image</title>
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<para >
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The following steps build and boot your modified kernel image:
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<orderedlist >
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<listitem > <para > <emphasis > Be sure your build environment is initialized</emphasis> :
Your environment should be set up since you previously sourced
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the <filename > &OE_INIT_FILE; </filename> script.
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If it is not, source the script again from <filename > poky</filename> .
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<literallayout class= 'monospaced' >
$ cd ~/poky
$ source &OE_INIT_FILE;
</literallayout>
</para> </listitem>
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<listitem > <para > <emphasis > Clean up</emphasis> :
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Be sure to clean the shared state out by running the
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<filename > cleansstate</filename> BitBake task as follows from your Build Directory:
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<literallayout class= 'monospaced' >
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$ bitbake -c cleansstate linux-yocto
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</literallayout> </para>
<para > <note > Never remove any files by hand from the <filename > tmp/deploy</filename>
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directory inside the Build Directory.
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Always use the various BitBake clean tasks to clear out previous
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build artifacts.
</note> </para> </listitem>
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<listitem > <para > <emphasis > Build the image</emphasis> :
Next, build the kernel image using this command:
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<literallayout class= 'monospaced' >
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$ bitbake -k linux-yocto
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</literallayout> </para> </listitem>
</orderedlist>
</para>
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</section>
2012-10-08 17:14:58 +00:00
2012-10-13 03:02:43 +00:00
<section id= 'verify-your-changes' >
<title > Verify Your Changes</title>
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<para >
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These steps boot the image and allow you to see the changes
<orderedlist >
<listitem > <para > <emphasis > Boot the image</emphasis> :
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Boot the modified image in the QEMU emulator
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using this command:
<literallayout class= 'monospaced' >
$ runqemu qemux86
</literallayout> </para> </listitem>
<listitem > <para > <emphasis > Verify the changes</emphasis> :
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Log into the machine using <filename > root</filename> with no password and then
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use the following shell command to scroll through the console's boot output.
<literallayout class= 'monospaced' >
# dmesg | less
</literallayout>
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You should see the results of your <filename > printk</filename> statements
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as part of the output.</para> </listitem>
</orderedlist>
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</para>
</section>
</section>
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<section id= "usingpoky-changes-updatingimages" >
<title > Updating Existing Images</title>
<para >
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Often, rather than re-flashing a new image, you might wish to install updated
packages into an existing running system.
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You can do this by first sharing the <filename > tmp/deploy/ipk/</filename> directory
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through a web server and then by changing <filename > /etc/opkg/base-feeds.conf</filename>
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to point at the shared server.
Following is an example:
<literallayout class= 'monospaced' >
$ src/gz all http://www.mysite.com/somedir/deploy/ipk/all
$ src/gz armv7a http://www.mysite.com/somedir/deploy/ipk/armv7a
$ src/gz beagleboard http://www.mysite.com/somedir/deploy/ipk/beagleboard
</literallayout>
</para>
</section>
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<section id= 'working-with-packages' >
<title > Working with Packages</title>
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<para >
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This section describes a few tasks that involve packages:
<itemizedlist >
<listitem > <para > Incrementing a package revision number
</para> </listitem>
<listitem > <para > Handling a package name alias
</para> </listitem>
<listitem > <para > Handling option module packaging
</para> </listitem>
</itemizedlist>
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</para>
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<section id= 'incrementing-a-package-revision-number' >
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<title > Incrementing a Package Revision Number</title>
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2012-11-12 19:35:06 +00:00
<para >
If a committed change results in changing the package output,
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then the value of the
2013-02-08 18:59:27 +00:00
<ulink url= '&YOCTO_DOCS_REF_URL;#var-PR' > <filename > PR</filename> </ulink>
variable needs to be increased (or "bumped").
Increasing <filename > PR</filename> occurs one of two ways:
<itemizedlist >
<listitem > <para > Automatically using a Package Revision
Service (PR Service).</para> </listitem>
<listitem > <para > Manually incrementing the
<filename > PR</filename> variable.</para> </listitem>
</itemizedlist>
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</para>
2012-03-05 19:09:31 +00:00
2012-11-12 19:35:06 +00:00
<para >
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Given that one of the challenges any build system and its
users face is how to maintain a package feed that is compatible
with existing package manager applications such as
RPM, APT, and OPKG, using an automated system is much
preferred over a manual system.
In either system, the main requirement is that version
numbering increases in a linear fashion and that a number of
version components exist that support that linear progression.
</para>
<para >
The following two sections provide information on the PR Service
and on manual <filename > PR</filename> bumping.
</para>
<section id= 'working-with-a-pr-service' >
<title > Working With a PR Service</title>
<para >
As mentioned, attempting to maintain revision numbers in the
<ulink url= '&YOCTO_DOCS_DEV_URL;#metadata' > Metadata</ulink>
is error prone, inaccurate and causes problems for people
submitting recipes.
Conversely, the PR Service automatically generates
increasing numbers, particularly the revision field,
which removes the human element.
<note >
For additional information on using a PR Service, you
can see the
<ulink url= '&YOCTO_WIKI_URL;/wiki/PR_Service' > PR Service</ulink>
wiki page.
</note>
</para>
<para >
The Yocto Project uses variables in order of
decreasing priority to facilitate revision numbering (i.e.
<ulink url= '&YOCTO_DOCS_REF_URL;#var-PE' > <filename > PE</filename> </ulink> ,
<ulink url= '&YOCTO_DOCS_REF_URL;#var-PV' > <filename > PV</filename> </ulink> , and
<ulink url= '&YOCTO_DOCS_REF_URL;#var-PR' > <filename > PR</filename> </ulink>
for epoch, version and revision, respectively).
The values are highly dependent on the policies and
procedures of a given distribution and package feed.
</para>
<para >
Because the OpenEmbedded build system uses "signatures",
which are unique to a given build, the build system
knows when to rebuild packages.
All the inputs into a given task are represented by a
signature, which can trigger a rebuild when different.
Thus, the build system itself does not rely on the
<filename > PR</filename> numbers to trigger a rebuild.
The signatures, however, can be used to generate
<filename > PR</filename> values.
</para>
<para >
The PR Service works with both
<filename > OEBasic</filename> and
<filename > OEBasicHash</filename> generators.
The value of <filename > PR</filename> bumps when the
checksum changes and the different generator mechanisms
change signatures under different circumstances.
</para>
<para >
As implemented, the build system includes values from
the PR Service into the <filename > PR</filename> field as
an addition using the form "<filename > .x</filename> " so
<filename > r0</filename> becomes <filename > r0.1</filename> ,
<filename > r0.2</filename> and so forth.
This scheme allows existing <filename > PR</filename> values
to be used for whatever reasons, which include manual
<filename > PR</filename> bumps should it be necessary.
</para>
<para >
By default, there is no server that runs the PR Service.
Thus, the packages generated are just "self consistent".
The build system adds and removes packages and
there are no guarantees about upgrade paths.
</para>
<para >
The simplest form for a PR Service is for it to exist
for a single host development system that builds the
package feed (building system).
For this scenario, you can enable the PR Service by adding
the following to your <filename > local.conf</filename>
file in the
<ulink url= '&YOCTO_DOCS_DEV_URL;#build-directory' > Build Directory</ulink> :
<literallayout class= 'monospaced' >
PRSERV_HOST = "localhost:0"
</literallayout>
Once the service is started, packages will automatically
get increasing <filename > PR</filename> values and
BitBake will take care of starting and stopping the server.
</para>
<para >
If you have a more complex setup where multiple host
development systems work against a common, shared package
feed, you have a single PR Service running and it is
connected to each building system.
For this scenario, you need to start the PR Service using
the <filename > bitbake-prserv</filename> command:
<literallayout class= 'monospaced' >
bitbake-prserve ‐ ‐ host < ip> ‐ ‐ port < port> ‐ ‐ start
</literallayout>
In addition to hand-starting the service, you need to
update the <filename > local.conf</filename> file of each
building system as described earlier so each system
points to the server and port.
</para>
<para >
It is also recommended you use build history, which adds
some sanity checks to package versions, in conjunction with
the server that is running the PR Service.
To enable build history, add the following to each building
system's <filename > local.conf</filename> file:
<literallayout class= 'monospaced' >
# It is recommended to activate "buildhistory" for testing the PR service
INHERIT += "buildhistory"
BUILDHISTORY_COMMIT = "1"
</literallayout>
For information on build history, see the
"<ulink url= '&YOCTO_DOCS_REF_URL;#maintaining-build-output-quality' > Maintaining Build Output Quality</ulink> "
section in the Yocto Project Reference Manual.
</para>
2008-02-26 11:31:34 +00:00
2013-02-08 18:59:27 +00:00
<note >
The OpenEmbedded build system does not maintain
<filename > PR</filename> information as part of the
shared state (sstate) packages.
If you maintain an sstate feed, its expected that either
all your building systems that contribute to the sstate
feed use a shared PR Service, or you do not run a PR
Service on any of your building systems.
Having some systems use a PR Service while others do
not leads to obvious problems.
</note>
</section>
<section id= 'manually-bumping-pr' >
<title > Manually Bumping PR</title>
<para >
If a committed change results in changing the package output,
then the value of the PR variable needs to be increased
(or "bumped") as part of that commit.
For new recipes you should add the <filename > PR</filename>
variable and set its initial value equal to "r0", which is the default.
Even though the default value is "r0", the practice of adding it to a new recipe makes
it harder to forget to bump the variable when you make changes
to the recipe in future.
</para>
<para >
If you are sharing a common <filename > .inc</filename> file with multiple recipes,
you can also use the
<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-INC_PR' > INC_PR</ulink> </filename>
variable to ensure that
the recipes sharing the <filename > .inc</filename> file are rebuilt when the
<filename > .inc</filename> file itself is changed.
The <filename > .inc</filename> file must set <filename > INC_PR</filename>
(initially to "r0"), and all recipes referring to it should set <filename > PR</filename>
to "$(INC_PR).0" initially, incrementing the last number when the recipe is changed.
If the <filename > .inc</filename> file is changed then its
<filename > INC_PR</filename> should be incremented.
</para>
<para >
When upgrading the version of a package, assuming the
<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-PV' > PV</ulink> </filename>
changes, the <filename > PR</filename> variable should be reset to "r0"
(or "$(INC_PR).0" if you are using <filename > INC_PR</filename> ).
</para>
<para >
Usually, version increases occur only to packages.
However, if for some reason <filename > PV</filename> changes but does not
increase, you can increase the
<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-PE' > PE</ulink> </filename>
variable (Package Epoch).
The <filename > PE</filename> variable defaults to "0".
</para>
<para >
Version numbering strives to follow the
<ulink url= 'http://www.debian.org/doc/debian-policy/ch-controlfields.html' >
Debian Version Field Policy Guidelines</ulink> .
These guidelines define how versions are compared and what "increasing" a version means.
</para>
<para >
There are two reasons for following the previously mentioned guidelines.
First, to ensure that when a developer updates and rebuilds, they get all the changes to
the repository and do not have to remember to rebuild any sections.
Second, to ensure that target users are able to upgrade their
devices using package manager commands such as <filename > opkg upgrade</filename>
(or similar commands for dpkg/apt or rpm-based systems).
</para>
<para >
The goal is to ensure the Yocto Project has packages that can be upgraded in all cases.
</para>
</section>
2012-11-12 19:35:06 +00:00
</section>
<section id= "usingpoky-configuring-DISTRO_PN_ALIAS" >
<title > Handling a Package Name Alias</title>
<para >
Sometimes a package name you are using might exist under an alias or as a similarly named
package in a different distribution.
The OpenEmbedded build system implements a <filename > distro_check</filename>
task that automatically connects to major distributions
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and checks for these situations.
If the package exists under a different name in a different distribution, you get a
<filename > distro_check</filename> mismatch.
You can resolve this problem by defining a per-distro recipe name alias using the
<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-DISTRO_PN_ALIAS' > DISTRO_PN_ALIAS</ulink> </filename>
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variable.
</para>
<para >
Following is an example that shows how you specify the <filename > DISTRO_PN_ALIAS</filename>
variable:
<literallayout class= 'monospaced' >
2011-12-08 21:22:23 +00:00
DISTRO_PN_ALIAS_pn-PACKAGENAME = "distro1=package_name_alias1 \
distro2=package_name_alias2 \
distro3=package_name_alias3 \
..."
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</literallayout>
</para>
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2012-11-12 19:35:06 +00:00
<para >
If you have more than one distribution alias, separate them with a space.
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Note that the build system currently automatically checks the
Fedora, OpenSuSE, Debian, Ubuntu,
and Mandriva distributions for source package recipes without having to specify them
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using the <filename > DISTRO_PN_ALIAS</filename> variable.
For example, the following command generates a report that lists the Linux distributions
that include the sources for each of the recipes.
<literallayout class= 'monospaced' >
2011-12-08 21:22:23 +00:00
$ bitbake world -f -c distro_check
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</literallayout>
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The results are stored in the <filename > build/tmp/log/distro_check-${DATETIME}.results</filename>
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file found in the Source Directory.
</para>
</section>
<section id= 'handling-optional-module-packaging' >
<title > Handling Optional Module Packaging</title>
<para >
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Many pieces of software split functionality into optional
modules (or plugins) and the plugins that are built
might depend on configuration options.
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To avoid having to duplicate the logic that determines what
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modules are available in your recipe or to avoid having
to package each module by hand, the OpenEmbedded build system
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provides functionality to handle module packaging dynamically.
</para>
<para >
To handle optional modual packaging, you need to do two things:
<itemizedlist >
<listitem > <para > Ensure the module packaging is actually
done</para> </listitem>
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<listitem > <para > Ensure that any dependencies on optional
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modules from other recipes are satisfied by your recipe
</para> </listitem>
</itemizedlist>
</para>
<section id= 'making-sure-the-packaging-is-done' >
<title > Making Sure the Packaging is Done</title>
<para >
To ensure the module packaging actually gets done, you use
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the <filename > do_split_packages</filename> function within
the <filename > populate_packages</filename> python function
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in your recipe.
The <filename > do_split_packages</filename> function
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searches for a pattern of files or directories under a
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specified path and creates a package for each one it finds
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by appending to the <filename > PACKAGES</filename> variable
and setting the appropriate values for
<filename > FILES_packagename</filename> ,
<filename > RDEPENDS_packagename</filename> ,
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<filename > DESCRIPTION_packagename</filename> , and so forth.
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Here is an example from the <filename > lighttpd</filename>
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recipe:
<literallayout class= 'monospaced' >
python populate_packages_prepend () {
lighttpd_libdir = d.expand('${libdir}')
do_split_packages(d, lighttpd_libdir, '^mod_(.*)\.so$',
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'lighttpd-module-%s', 'Lighttpd module for %s',
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extra_depends='')
}
</literallayout>
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The previous example specifies a number of things in the
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call to <filename > do_split_packages</filename> .
<itemizedlist >
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<listitem > <para > A directory within the files installed
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by your recipe through <filename > do_install</filename>
in which to search.</para> </listitem>
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<listitem > <para > A regular expression to match module
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files in that directory.
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In the example, note the parentheses () that mark
the part of the expression from which the module
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name should be derived.</para> </listitem>
<listitem > <para > A pattern to use for the package names.
</para> </listitem>
<listitem > <para > A description for each package.
</para> </listitem>
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<listitem > <para > An empty string for
<filename > extra_depends</filename> , which disables
the default dependency on the main
<filename > lighttpd</filename> package.
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Thus, if a file in <filename > ${libdir}</filename>
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called <filename > mod_alias.so</filename> is found,
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a package called <filename > lighttpd-module-alias</filename>
is created for it and the <filename > DESCRIPTION</filename>
is set to "Lighttpd module for alias".</para> </listitem>
</itemizedlist>
</para>
<para >
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Often, packaging modules is as simple as the previous
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example.
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However, more advanced options exist that you can employ
to <filename > do_split_packages</filename> to modify its
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behavior.
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And, if you need to, you can add more logic by specifying
a hook function that is called for each package.
It is also perfectly acceptable to call
<filename > do_split_packages</filename> multiple times if
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you have more than one set of modules to package.
</para>
<para >
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For more examples that show how to use
<filename > do_split_packages</filename> , see the
<filename > connman.inc</filename> file in the
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<filename > meta/recipes-connectivity/connman/</filename>
directory of the <filename > poky</filename> source repository.
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You can also find examples in
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<filename > meta/classes/kernel.bbclass</filename> .
</para>
<para >
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Following is a reference that shows
<filename > do_split_packages</filename> mandatory and
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optional arguments:
<literallayout class= 'monospaced' >
Mandatory arguments
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root
The path in which to search
file_regex
Regular expression to match searched files.
Use parentheses () to mark the part of this
expression that should be used to derive the
module name (to be substituted where %s is
used in other function arguments as noted below)
output_pattern
Pattern to use for the package names. Must
include %s.
description
Description to set for each package. Must
include %s.
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Optional arguments
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postinst
Postinstall script to use for all packages
(as a string)
recursive
True to perform a recursive search - default
False
hook
A hook function to be called for every match.
The function will be called with the following
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arguments (in the order listed):
f
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Full path to the file/directory match
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pkg
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The package name
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file_regex
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As above
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output_pattern
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As above
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modulename
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The module name derived using file_regex
extra_depends
Extra runtime dependencies (RDEPENDS) to be
set for all packages. The default value of None
causes a dependency on the main package
(${PN}) - if you do not want this, pass empty
string '' for this parameter.
aux_files_pattern
Extra item(s) to be added to FILES for each
package. Can be a single string item or a list
of strings for multiple items. Must include %s.
postrm
postrm script to use for all packages (as a
string)
allow_dirs
True to allow directories to be matched -
default False
prepend
If True, prepend created packages to PACKAGES
instead of the default False which appends them
match_path
match file_regex on the whole relative path to
the root rather than just the file name
aux_files_pattern_verbatim
Extra item(s) to be added to FILES for each
package, using the actual derived module name
rather than converting it to something legal
for a package name. Can be a single string item
or a list of strings for multiple items. Must
include %s.
allow_links
True to allow symlinks to be matched - default
False
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</literallayout>
</para>
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</section>
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<section id= 'satisfying-dependencies' >
<title > Satisfying Dependencies</title>
<para >
The second part for handling optional module packaging
is to ensure that any dependencies on optional modules
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from other recipes are satisfied by your recipe.
You can be sure these dependencies are satisfied by
using the
<ulink url= '&YOCTO_DOCS_REF_URL;#var-PACKAGES_DYNAMIC' > <filename > PACKAGES_DYNAMIC</filename> </ulink> variable.
Here is an example that continues with the
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<filename > lighttpd</filename> recipe shown earlier:
<literallayout class= 'monospaced' >
PACKAGES_DYNAMIC = "lighttpd-module-.*"
</literallayout>
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The name specified in the regular expression can of
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course be anything.
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In this example, it is <filename > lighttpd-module-</filename>
and is specified as the prefix to ensure that any
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<ulink url= '&YOCTO_DOCS_REF_URL;#var-RDEPENDS' > <filename > RDEPENDS</filename> </ulink>
and <ulink url= '&YOCTO_DOCS_REF_URL;#var-RRECOMMENDS' > <filename > RRECOMMENDS</filename> </ulink>
on a package name starting with the prefix are satisfied
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during build time.
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If you are using <filename > do_split_packages</filename>
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as described in the previous section, the value you put in
<filename > PACKAGES_DYNAMIC</filename> should correspond to
the name pattern specified in the call to
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<filename > do_split_packages</filename> .
</para>
</section>
</section>
2010-05-26 14:26:09 +00:00
</section>
2010-11-04 21:12:46 +00:00
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<section id= "building-software-from-an-external-source" >
<title > Building Software from an External Source</title>
<para >
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By default, the OpenEmbedded build system does its work from within the
<link linkend= 'build-directory' > Build Directory</link> .
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The build process involves fetching the source files, unpacking them, and then patching them
if necessary before the build takes place.
</para>
<para >
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Situations exist where you might want to build software from source files that are external to
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and thus outside of the <link linkend= 'source-directory' > Source Directory</link> .
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For example, suppose you have a project that includes a new BSP with a heavily customized
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kernel, a very minimal image, and some new user-space recipes.
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And, you want to minimize exposing the build system to the
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development team so that they can focus on their project and maintain everyone's workflow
as much as possible.
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In this case, you want a kernel source directory on the development machine where the
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development occurs.
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You want the recipe's
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<ulink url= '&YOCTO_DOCS_REF_URL;#var-SRC_URI' > <filename > SRC_URI</filename> </ulink>
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variable to point to the external directory and use it as is, not copy it.
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</para>
<para >
To build from software that comes from an external source, all you need to do is
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change your recipe so that it inherits the
<ulink url= '&YOCTO_DOCS_REF_URL;#ref-classes-externalsrc' > <filename > externalsrc.bbclass</filename> </ulink>
class and then sets the
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<ulink url= '&YOCTO_DOCS_REF_URL;#var-S' > <filename > S</filename> </ulink>
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variable to point to your external source code.
Here are the statements to put in your recipe:
<literallayout class= 'monospaced' >
inherit externalsrc
S = "/some/path/to/your/package/source"
</literallayout>
</para>
<para >
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It is important to know that the <filename > externalsrc.bbclass</filename> assumes that the
source directory <filename > S</filename> and the Build Directory
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<ulink url= '&YOCTO_DOCS_REF_URL;#var-B' > <filename > B</filename> </ulink>
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are different even though by default these directories are the same.
This assumption is important because it supports building different variants of the recipe
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by using the
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<ulink url= '&YOCTO_DOCS_REF_URL;#var-BBCLASSEXTEND' > <filename > BBCLASSEXTEND</filename> </ulink>
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variable.
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You could allow the Build Directory to be the same as the source directory but you would
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not be able to build more than one variant of the recipe.
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Consequently, if you are building multiple variants of the recipe, you need to establish a
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Build Directory that is different than the source directory.
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</para>
</section>
2012-03-29 21:54:55 +00:00
2012-03-30 14:33:09 +00:00
<section id= 'excluding-recipes-from-the-build' >
<title > Excluding Recipes From the Build</title>
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2012-03-29 22:07:23 +00:00
<para >
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You might find that there are groups of recipes or append files
that you want to filter out of the build process.
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For example, recipes you know you will never use or want should not
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be part of the build.
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Removing these files from parsing speeds up parts of the build.
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</para>
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<para >
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It is possible to filter or mask out <filename > .bb</filename> and
<filename > .bbappend</filename> files.
You can do this by providing an expression with the
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<ulink url= '&YOCTO_DOCS_REF_URL;#var-BBMASK' > <filename > BBMASK</filename> </ulink>
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variable.
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Here is an example:
<literallayout class= 'monospaced' >
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BBMASK = "/meta-mymachine/recipes-maybe/"
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</literallayout>
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Here, all <filename > .bb</filename> and
<filename > .bbappend</filename> files in the directory that matches
the expression are ignored during the build process.
See the glossary entry for the
<ulink url= '&YOCTO_DOCS_REF_URL;#var-BBMASK' > <filename > BBMASK</filename> </ulink>
variable for more information.
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</para>
2013-01-30 21:42:26 +00:00
<note >
The value you provide is passed to python's regular expression
compiler.
The expression is compared against the full paths to the files.
For complete syntax information, see python's documentation at
<ulink url= 'http://docs.python.org/release/2.3/lib/re-syntax.html' > </ulink> .
</note>
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</section>
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<section id= "platdev-appdev-srcrev" >
<title > Using an External SCM</title>
<para >
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If you're working on a recipe that pulls from an external Source Code Manager (SCM), it
is possible to have the OpenEmbedded build system notice new recipe changes added to the
SCM and then build the resulting package that depends on the new recipes by using the latest
versions.
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This only works for SCMs from which it is possible to get a sensible revision number for changes.
Currently, you can do this with Apache Subversion (SVN), Git, and Bazaar (BZR) repositories.
</para>
<para >
To enable this behavior, simply add the following to the <filename > local.conf</filename>
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configuration file found in the
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<ulink url= '&YOCTO_DOCS_DEV_URL;#build-directory' > Build Directory</ulink> :
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<literallayout class= 'monospaced' >
SRCREV_pn-< PN> = "${AUTOREV}"
</literallayout>
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where <ulink url= '&YOCTO_DOCS_REF_URL;#var-PN' > <filename > PN</filename> </ulink>
is the name of the recipe for which you want to enable automatic source
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revision updating.
</para>
</section>
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<section id= "platdev-gdb-remotedebug" >
<title > Debugging With the GNU Project Debugger (GDB) Remotely</title>
<para >
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GDB allows you to examine running programs, which in turn helps you to understand and fix problems.
It also allows you to perform post-mortem style analysis of program crashes.
GDB is available as a package within the Yocto Project and by default is
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installed in SDK images.
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See the "<ulink url= '&YOCTO_DOCS_REF_URL;#ref-images' > Images</ulink> " chapter
in the Yocto Project Reference Manual for a description of these images.
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You can find information on GDB at <ulink url= "http://sourceware.org/gdb/" /> .
</para>
<tip >
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For best results, install <filename > -dbg</filename> packages for the applications
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you are going to debug.
Doing so makes available extra debug symbols that give you more meaningful output.
</tip>
<para >
Sometimes, due to memory or disk space constraints, it is not possible
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to use GDB directly on the remote target to debug applications.
These constraints arise because GDB needs to load the debugging information and the
binaries of the process being debugged.
Additionally, GDB needs to perform many computations to locate information such as function
names, variable names and values, stack traces and so forth - even before starting the
debugging process.
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These extra computations place more load on the target system and can alter the
characteristics of the program being debugged.
</para>
<para >
To help get past the previously mentioned constraints, you can use Gdbserver.
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Gdbserver runs on the remote target and does not load any debugging information
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from the debugged process.
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Instead, a GDB instance processes the debugging information that is run on a
remote computer - the host GDB.
The host GDB then sends control commands to Gdbserver to make it stop or start the debugged
program, as well as read or write memory regions of that debugged program.
All the debugging information loaded and processed as well
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as all the heavy debugging is done by the host GDB.
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Offloading these processes gives the Gdbserver running on the target a chance to remain
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small and fast.
</para>
<para >
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Because the host GDB is responsible for loading the debugging information and
for doing the necessary processing to make actual debugging happen, the
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user has to make sure the host can access the unstripped binaries complete
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with their debugging information and also be sure the target is compiled with no optimizations.
The host GDB must also have local access to all the libraries used by the
debugged program.
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Because Gdbserver does not need any local debugging information, the binaries on
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the remote target can remain stripped.
However, the binaries must also be compiled without optimization
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so they match the host's binaries.
</para>
<para >
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To remain consistent with GDB documentation and terminology, the binary being debugged
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on the remote target machine is referred to as the "inferior" binary.
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For documentation on GDB see the
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<ulink url= "http://sourceware.org/gdb/documentation/" > GDB site</ulink> .
</para>
<section id= "platdev-gdb-remotedebug-launch-gdbserver" >
<title > Launching Gdbserver on the Target</title>
<para >
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First, make sure Gdbserver is installed on the target.
If it is not, install the package <filename > gdbserver</filename> , which needs the
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<filename > libthread-db1</filename> package.
</para>
<para >
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As an example, to launch Gdbserver on the target and make it ready to "debug" a
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program located at <filename > /path/to/inferior</filename> , connect
to the target and launch:
<literallayout class= 'monospaced' >
$ gdbserver localhost:2345 /path/to/inferior
</literallayout>
Gdbserver should now be listening on port 2345 for debugging
commands coming from a remote GDB process that is running on the host computer.
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Communication between Gdbserver and the host GDB are done using TCP.
To use other communication protocols, please refer to the
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<ulink url= 'http://www.gnu.org/software/gdb/' > Gdbserver documentation</ulink> .
</para>
</section>
<section id= "platdev-gdb-remotedebug-launch-gdb" >
<title > Launching GDB on the Host Computer</title>
<para >
Running GDB on the host computer takes a number of stages.
This section describes those stages.
</para>
<section id= "platdev-gdb-remotedebug-launch-gdb-buildcross" >
<title > Building the Cross-GDB Package</title>
<para >
A suitable GDB cross-binary is required that runs on your host computer but
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also knows about the the ABI of the remote target.
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You can get this binary from the meta-toolchain.
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Here is an example:
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<literallayout class= 'monospaced' >
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/usr/local/poky/eabi-glibc/arm/bin/arm-poky-linux-gnueabi-gdb
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</literallayout>
where <filename > arm</filename> is the target architecture and
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<filename > linux-gnueabi</filename> the target ABI.
</para>
<para >
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Alternatively, you can use BitBake to build the <filename > gdb-cross</filename> binary.
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Here is an example:
<literallayout class= 'monospaced' >
$ bitbake gdb-cross
</literallayout>
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Once the binary is built, you can find it here:
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<literallayout class= 'monospaced' >
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tmp/sysroots/< host-arch> /usr/bin/< target-abi> -gdb
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</literallayout>
</para>
</section>
<section id= "platdev-gdb-remotedebug-launch-gdb-inferiorbins" >
<title > Making the Inferior Binaries Available</title>
<para >
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The inferior binary (complete with all debugging symbols), as well as any
libraries (and their debugging symbols) on which the inferior binary depends,
needs to be available.
There are a number of ways you can make these items available.
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</para>
<para >
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Perhaps the easiest way is to have an SDK image that corresponds to the plain
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image installed on the device.
In the case of <filename > core-image-sato</filename> ,
<filename > core-image-sato-sdk</filename> would contain suitable symbols.
Because the SDK images already have the debugging symbols installed, it is just a
question of expanding the archive to some location and then informing GDB.
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</para>
<para >
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Alternatively, the OpenEmbedded build system can build a custom directory of files
for a specific
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debugging purpose by reusing its <filename > tmp/rootfs</filename> directory.
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This directory contains the contents of the last built image.
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This process assumes two things:
<itemizedlist >
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<listitem > <para > The image running on the target was the last image to
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be built.</para> </listitem>
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<listitem > <para > The package (<filename > foo</filename> in the following
example) that contains the inferior binary to be debugged has been built
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without optimization and has debugging information available.</para> </listitem>
</itemizedlist>
</para>
<para >
The following steps show how to build the custom directory of files:
<orderedlist >
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<listitem > <para > Install the package (<filename > foo</filename> in this case) to
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<filename > tmp/rootfs</filename> :
<literallayout class= 'monospaced' >
$ tmp/sysroots/i686-linux/usr/bin/opkg-cl -f \
tmp/work/< target-abi> /core-image-sato-1.0-r0/temp/opkg.conf -o \
tmp/rootfs/ update
</literallayout> </para> </listitem>
<listitem > <para > Install the debugging information:
<literallayout class= 'monospaced' >
$ tmp/sysroots/i686-linux/usr/bin/opkg-cl -f \
tmp/work/< target-abi> /core-image-sato-1.0-r0/temp/opkg.conf \
-o tmp/rootfs install foo
$ tmp/sysroots/i686-linux/usr/bin/opkg-cl -f \
tmp/work/< target-abi> /core-image-sato-1.0-r0/temp/opkg.conf \
-o tmp/rootfs install foo-dbg
</literallayout> </para> </listitem>
</orderedlist>
</para>
</section>
<section id= "platdev-gdb-remotedebug-launch-gdb-launchhost" >
<title > Launch the Host GDB</title>
<para >
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To launch the host GDB, you run the <filename > cross-gdb</filename> binary and provide
the inferior binary as part of the command line.
For example, the following command form continues with the example used in
the previous section.
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This command form loads the <filename > foo</filename> binary
as well as the debugging information:
<literallayout class= 'monospaced' >
$ < target-abi> -gdb rootfs/usr/bin/foo
</literallayout>
Once the GDB prompt appears, you must instruct GDB to load all the libraries
of the inferior binary from <filename > tmp/rootfs</filename> as follows:
<literallayout class= 'monospaced' >
$ set solib-absolute-prefix /path/to/tmp/rootfs
</literallayout>
The pathname <filename > /path/to/tmp/rootfs</filename> must either be
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the absolute path to <filename > tmp/rootfs</filename> or the location at which
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binaries with debugging information reside.
</para>
<para >
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At this point you can have GDB connect to the Gdbserver that is running
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on the remote target by using the following command form:
<literallayout class= 'monospaced' >
$ target remote remote-target-ip-address:2345
</literallayout>
The <filename > remote-target-ip-address</filename> is the IP address of the
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remote target where the Gdbserver is running.
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Port 2345 is the port on which the GDBSERVER is running.
</para>
</section>
<section id= "platdev-gdb-remotedebug-launch-gdb-using" >
<title > Using the Debugger</title>
<para >
You can now proceed with debugging as normal - as if you were debugging
on the local machine.
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For example, to instruct GDB to break in the "main" function and then
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continue with execution of the inferior binary use the following commands
from within GDB:
<literallayout class= 'monospaced' >
(gdb) break main
(gdb) continue
</literallayout>
</para>
<para >
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For more information about using GDB, see the project's online documentation at
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<ulink url= "http://sourceware.org/gdb/download/onlinedocs/" /> .
</para>
</section>
</section>
</section>
<section id= "platdev-oprofile" >
<title > Profiling with OProfile</title>
<para >
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<ulink url= "http://oprofile.sourceforge.net/" > OProfile</ulink> is a
statistical profiler well suited for finding performance
bottlenecks in both userspace software and in the kernel.
This profiler provides answers to questions like "Which functions does my application spend
the most time in when doing X?"
Because the OpenEmbedded build system is well integrated with OProfile, it makes profiling
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applications on target hardware straightforward.
2013-01-25 20:18:23 +00:00
<note >
For more information on how to set up and run OProfile, see the
"<ulink url= '&YOCTO_DOCS_PROF_URL;#profile-manual-oprofile' > OProfile</ulink> "
section in the Yocto Project Profiling and Tracing Manual.
</note>
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</para>
<para >
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To use OProfile, you need an image that has OProfile installed.
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The easiest way to do this is with <filename > tools-profile</filename> in the
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<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-IMAGE_FEATURES' > IMAGE_FEATURES</ulink> </filename> variable.
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You also need debugging symbols to be available on the system where the analysis
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takes place.
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You can gain access to the symbols by using <filename > dbg-pkgs</filename> in the
<filename > IMAGE_FEATURES</filename> variable or by
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installing the appropriate <filename > -dbg</filename> packages.
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</para>
<para >
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For successful call graph analysis, the binaries must preserve the frame
pointer register and should also be compiled with the
<filename > -fno-omit-framepointer</filename> flag.
You can achieve this by setting the
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<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-SELECTED_OPTIMIZATION' > SELECTED_OPTIMIZATION</ulink> </filename>
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variable with the following options:
<literallayout class= 'monospaced' >
-fexpensive-optimizations
-fno-omit-framepointer
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-frename-registers
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-O2
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</literallayout>
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You can also achieve it by setting the
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<filename > <ulink url= '&YOCTO_DOCS_REF_URL;#var-DEBUG_BUILD' > DEBUG_BUILD</ulink> </filename>
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variable to "1" in the <filename > local.conf</filename> configuration file.
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If you use the <filename > DEBUG_BUILD</filename> variable,
you will also add extra debug information that can make the debug packages large.
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</para>
<section id= "platdev-oprofile-target" >
<title > Profiling on the Target</title>
<para >
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Using OProfile you can perform all the profiling work on the target device.
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A simple OProfile session might look like the following:
</para>
<para >
<literallayout class= 'monospaced' >
# opcontrol --reset
# opcontrol --start --separate=lib --no-vmlinux -c 5
.
.
[do whatever is being profiled]
.
.
# opcontrol --stop
$ opreport -cl
</literallayout>
</para>
<para >
In this example, the <filename > reset</filename> command clears any previously profiled data.
The next command starts OProfile.
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The options used when starting the profiler separate dynamic library data
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within applications, disable kernel profiling, and enable callgraphing up to
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five levels deep.
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<note >
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To profile the kernel, you would specify the
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<filename > --vmlinux=/path/to/vmlinux</filename> option.
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The <filename > vmlinux</filename> file is usually in the source directory in the
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<filename > /boot/</filename> directory and must match the running kernel.
</note>
</para>
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<para >
After you perform your profiling tasks, the next command stops the profiler.
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After that, you can view results with the <filename > opreport</filename> command with options
to see the separate library symbols and callgraph information.
</para>
<para >
Callgraphing logs information about time spent in functions and about a function's
calling function (parent) and called functions (children).
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The higher the callgraphing depth, the more accurate the results.
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However, higher depths also increase the logging overhead.
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Consequently, you should take care when setting the callgraphing depth.
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<note >
On ARM, binaries need to have the frame pointer enabled for callgraphing to work.
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To accomplish this use the <filename > -fno-omit-framepointer</filename> option
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with <filename > gcc</filename> .
</note>
</para>
<para >
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For more information on using OProfile, see the OProfile
online documentation at
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<ulink url= "http://oprofile.sourceforge.net/docs/" /> .
</para>
</section>
<section id= "platdev-oprofile-oprofileui" >
<title > Using OProfileUI</title>
<para >
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A graphical user interface for OProfile is also available.
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You can download and build this interface from the Yocto Project at
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<ulink url= "&YOCTO_GIT_URL;/cgit.cgi/oprofileui/" > </ulink> .
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If the "tools-profile" image feature is selected, all necessary binaries
are installed onto the target device for OProfileUI interaction.
</para>
<para >
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Even though the source directory usually includes all needed patches on the target device, you
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might find you need other OProfile patches for recent OProfileUI features.
If so, see the <ulink url= '&YOCTO_GIT_URL;/cgit.cgi/oprofileui/tree/README' >
OProfileUI README</ulink> for the most recent information.
</para>
<section id= "platdev-oprofile-oprofileui-online" >
<title > Online Mode</title>
<para >
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Using OProfile in online mode assumes a working network connection with the target
hardware.
With this connection, you just need to run "oprofile-server" on the device.
By default, OProfile listens on port 4224.
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<note >
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You can change the port using the <filename > --port</filename> command-line
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option.
</note>
</para>
<para >
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The client program is called <filename > oprofile-viewer</filename> and its UI is relatively
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straightforward.
You access key functionality through the buttons on the toolbar, which
are duplicated in the menus.
Here are the buttons:
<itemizedlist >
<listitem > <para > <emphasis > Connect:</emphasis> Connects to the remote host.
You can also supply the IP address or hostname.</para> </listitem>
<listitem > <para > <emphasis > Disconnect:</emphasis> Disconnects from the target.
</para> </listitem>
<listitem > <para > <emphasis > Start:</emphasis> Starts profiling on the device.
</para> </listitem>
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<listitem > <para > <emphasis > Stop:</emphasis> Stops profiling on the device and
downloads the data to the local host.
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Stopping the profiler generates the profile and displays it in the viewer.
</para> </listitem>
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<listitem > <para > <emphasis > Download:</emphasis> Downloads the data from the
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target and generates the profile, which appears in the viewer.</para> </listitem>
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<listitem > <para > <emphasis > Reset:</emphasis> Resets the sample data on the device.
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Resetting the data removes sample information collected from previous
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sampling runs.
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Be sure you reset the data if you do not want to include old sample information.
</para> </listitem>
<listitem > <para > <emphasis > Save:</emphasis> Saves the data downloaded from the
target to another directory for later examination.</para> </listitem>
<listitem > <para > <emphasis > Open:</emphasis> Loads previously saved data.
</para> </listitem>
</itemizedlist>
</para>
<para >
The client downloads the complete 'profile archive' from
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the target to the host for processing.
This archive is a directory that contains the sample data, the object files,
and the debug information for the object files.
The archive is then converted using the <filename > oparchconv</filename> script, which is
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included in this distribution.
The script uses <filename > opimport</filename> to convert the archive from
the target to something that can be processed on the host.
</para>
<para >
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Downloaded archives reside in the Build Directory in
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<filename > /tmp</filename> and are cleared up when they are no longer in use.
</para>
<para >
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If you wish to perform kernel profiling, you need to be sure
a <filename > vmlinux</filename> file that matches the running kernel is available.
In the source directory, that file is usually located in
<filename > /boot/vmlinux-KERNELVERSION</filename> , where
<filename > KERNEL-version</filename> is the version of the kernel.
The OpenEmbedded build system generates separate <filename > vmlinux</filename>
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packages for each kernel it builds.
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Thus, it should just be a question of making sure a matching package is
installed (e.g. <filename > opkg install kernel-vmlinux</filename> .
The files are automatically installed into development and profiling images
alongside OProfile.
A configuration option exists within the OProfileUI settings page that you can use to
enter the location of the <filename > vmlinux</filename> file.
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</para>
<para >
Waiting for debug symbols to transfer from the device can be slow, and it
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is not always necessary to actually have them on the device for OProfile use.
All that is needed is a copy of the filesystem with the debug symbols present
on the viewer system.
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The "<link linkend= 'platdev-gdb-remotedebug-launch-gdb' > Launching GDB on the Host Computer</link> "
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section covers how to create such a directory with
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the source directory and how to use the OProfileUI Settings dialog to specify the location.
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If you specify the directory, it will be used when the file checksums
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match those on the system you are profiling.
</para>
</section>
<section id= "platdev-oprofile-oprofileui-offline" >
<title > Offline Mode</title>
<para >
If network access to the target is unavailable, you can generate
an archive for processing in <filename > oprofile-viewer</filename> as follows:
<literallayout class= 'monospaced' >
# opcontrol --reset
# opcontrol --start --separate=lib --no-vmlinux -c 5
.
.
[do whatever is being profiled]
.
.
# opcontrol --stop
# oparchive -o my_archive
</literallayout>
</para>
<para >
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In the above example, <filename > my_archive</filename> is the name of the
archive directory where you would like the profile archive to be kept.
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After the directory is created, you can copy it to another host and load it
using <filename > oprofile-viewer</filename> open functionality.
If necessary, the archive is converted.
</para>
</section>
</section>
</section>
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<section id= 'maintaining-open-source-license-compliance-during-your-products-lifecycle' >
<title > Maintaining Open Source License Compliance During Your Product's Lifecycle</title>
<para >
One of the concerns for a development organization using open source
software is how to maintain compliance with various open source
licensing during the lifecycle of the product.
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While this section does not provide legal advice or
comprehensively cover all scenarios, it does
present methods that you can use to
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assist you in meeting the compliance requirements during a software
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release.
</para>
<para >
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With hundreds of different open source licenses that the Yocto
Project tracks, it is difficult to know the requirements of each
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and every license.
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However, we can begin to cover the requirements of the major FLOSS licenses, by
assuming that there are three main areas of concern:
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<itemizedlist >
<listitem > <para > Source code must be provided.</para> </listitem>
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<listitem > <para > License text for the software must be
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provided.</para> </listitem>
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<listitem > <para > Compilation scripts and modifications to the
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source code must be provided.
</para> </listitem>
</itemizedlist>
There are other requirements beyond the scope of these
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three and the methods described in this section
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(e.g. the mechanism through which source code is distributed).
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As different organizations have different methods of complying with
open source licensing, this section is not meant to imply that
there is only one single way to meet your compliance obligations,
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but rather to describe one method of achieving compliance.
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</para>
<para >
The remainder of this section describes methods supported to meet the
previously mentioned three requirements.
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Once you take steps to meet these requirements,
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and prior to releasing images, sources, and the build system,
you should audit all artifacts to ensure completeness.
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The Yocto Project generates a license manifest during
image creation that is located
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in <filename > ${DEPLOY_DIR}/licenses/< image_name-datestamp> </filename>
to assist with any audits.
</para>
<section id= 'providing-the-source-code' >
<title > Providing the Source Code</title>
<para >
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Compliance activities should begin before you generate the
final image.
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The first thing you should look at is the requirement that
tops the list for most compliance groups - providing
the source.
The Yocto Project has a few ways of meeting this
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requirement.
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</para>
<para >
One of the easiest ways to meet this requirement is
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to provide the entire
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<ulink url= '&YOCTO_DOCS_REF_URL;#var-DL_DIR' > <filename > DL_DIR</filename> </ulink>
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used by the build.
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This method, however, has a few issues.
The most obvious is the size of the directory since it includes
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all sources used in the build and not just the source used in
the released image.
It will include toolchain source, and other artifacts which
you would not generally release.
But, the more serious issue for most companies is accidental
release of proprietary software.
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The Yocto Project provides an archiver class to help avoid
some of these concerns.
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</para>
<para >
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Before you employ <filename > DL_DIR</filename> or the
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archiver class, you need to decide how you choose to
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provide source.
The source archiver class can generate tarballs and SRPMs
and can create them with various levels of compliance in mind.
One way of doing this (but certainly not the only way) is to
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release just the original source as a tarball.
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You can do this by adding the following to the
<filename > local.conf</filename> file found in the
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<link linkend= 'build-directory' > Build Directory</link> :
<literallayout class= 'monospaced' >
ARCHIVER_MODE ?= "original"
ARCHIVER_CLASS = "${@'archive-${ARCHIVER_MODE}-source' if
ARCHIVER_MODE != 'none' else ''}"
INHERIT += "${ARCHIVER_CLASS}"
SOURCE_ARCHIVE_PACKAGE_TYPE = "tar"
</literallayout>
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During the creation of your image, the source from all
recipes that deploy packages to the image is placed within
subdirectories of
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<filename > DEPLOY_DIR/sources</filename> based on the
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<ulink url= '&YOCTO_DOCS_REF_URL;#var-LICENSE' > <filename > LICENSE</filename> </ulink>
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for each recipe.
Releasing the entire directory enables you to comply with
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requirements concerning providing the unmodified source.
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It is important to note that the size of the directory can
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get large.
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</para>
<para >
A way to help mitigate the size issue is to only release
tarballs for licenses that require the release of
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source.
Let's assume you are only concerned with GPL code as
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identified with the following:
<literallayout class= 'monospaced' >
$ cd poky/build/tmp/deploy/sources
$ mkdir ~/gpl_source_release
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$ for dir in */*GPL*; do cp -r $dir ~/gpl_source_release; done
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</literallayout>
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At this point, you could create a tarball from the
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<filename > gpl_source_release</filename> directory and
provide that to the end user.
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This method would be a step toward achieving compliance
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with section 3a of GPLv2 and with section 6 of GPLv3.
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</para>
</section>
<section id= 'providing-license-text' >
<title > Providing License Text</title>
<para >
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One requirement that is often overlooked is inclusion
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of license text.
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This requirement also needs to be dealt with prior to
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generating the final image.
Some licenses require the license text to accompany
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the binary.
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You can achieve this by adding the following to your
<filename > local.conf</filename> file:
<literallayout class= 'monospaced' >
COPY_LIC_MANIFEST = "1"
COPY_LIC_DIRS = "1"
</literallayout>
Adding these statements to the configuration file ensures
that the licenses collected during package generation
are included on your image.
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As the source archiver has already archived the original
unmodified source which would contain the license files,
you would have already met the requirements for inclusion
of the license information with source as defined by the GPL
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and other open source licenses.
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</para>
</section>
<section id= 'providing-compilation-scripts-and-source-code-modifications' >
<title > Providing Compilation Scripts and Source Code Modifications</title>
<para >
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At this point, we have addressed all we need to address
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prior to generating the image.
The next two requirements are addressed during the final
packaging of the release.
</para>
<para >
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By releasing the version of the OpenEmbedded build system
and the layers used during the build, you will be providing both
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compilation scripts and the source code modifications in one
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step.
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</para>
<para >
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If the deployment team has a
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<ulink url= '&YOCTO_DOCS_BSP_URL;#bsp-layers' > BSP layer</ulink>
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and a distro layer, and those those layers are used to patch,
compile, package, or modify (in any way) any open source
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software included in your released images, you
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may be required to to release those layers under section 3 of
GPLv2 or section 1 of GPLv3.
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One way of doing that is with a clean
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checkout of the version of the Yocto Project and layers used
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during your build.
Here is an example:
<literallayout class= 'monospaced' >
# We built using the &DISTRO_NAME; branch of the poky repo
$ git clone -b &DISTRO_NAME; git://git.yoctoproject.org/poky
$ cd poky
# We built using the release_branch for our layers
$ git clone -b release_branch git://git.mycompany.com/meta-my-bsp-layer
$ git clone -b release_branch git://git.mycompany.com/meta-my-software-layer
# clean up the .git repos
$ find . -name ".git" -type d -exec rm -rf {} \;
</literallayout>
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One thing a development organization might want to consider
for end-user convenience is to modify
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<filename > meta-yocto/conf/bblayers.conf.sample</filename> to
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ensure that when the end user utilizes the released build
system to build an image, the development organization's
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layers are included in the <filename > bblayers.conf</filename>
file automatically:
<literallayout class= 'monospaced' >
# LAYER_CONF_VERSION is increased each time build/conf/bblayers.conf
# changes incompatibly
LCONF_VERSION = "6"
BBPATH = "${TOPDIR}"
BBFILES ?= ""
BBLAYERS ?= " \
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##COREBASE##/meta \
##COREBASE##/meta-yocto \
##COREBASE##/meta-yocto-bsp \
##COREBASE##/meta-mylayer \
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"
BBLAYERS_NON_REMOVABLE ?= " \
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##COREBASE##/meta \
##COREBASE##/meta-yocto \
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"
</literallayout>
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Creating and providing an archive of the metadata layers
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(recipes, configuration files, and so forth)
enables you to meet your
requirements to include the scripts to control compilation
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as well as any modifications to the original source.
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</para>
</section>
</section>
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</chapter>
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