Performed general edits to this chapter.
many english corrections performed. Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
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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">
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<chapter id='bsp'>
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<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<chapter id="bsp">
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<title>Board Support Packages (BSP) - Developers Guide</title>
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<para>
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A Board Support Package (BSP) is a collection of information which together
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A Board Support Package (BSP) is a collection of information that
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defines how to support a particular hardware device, set of devices, or
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hardware platform. It will include information about the hardware features
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hardware platform.
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The BSP includes information about the hardware features
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present on the device and kernel configuration information along with any
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additional hardware drivers required. It will also list any additional software
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additional hardware drivers required.
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The BSP also lists any additional software
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components required in addition to a generic Linux software stack for both
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essential and optional platform features.
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</para>
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<para>
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The intent of this document is to define a structure for these components
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so that BSPs follow a commonly understood layout, allowing them to be
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provided in a common form that everyone understands. It also allows end-users
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to become familiar with one common format and encourages standardisation
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so that BSPs follow a commonly understood layout.
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Providing a common form allows end-users to understand and become familiar
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with the layout.
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A common form also encourages standardization
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of software support of hardware.
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</para>
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<para>
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The proposed format does have elements that are specific to the Poky and
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OpenEmbedded build systems. It is intended that this information can be
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used by other systems besides Poky/OpenEmbedded and that it will be simple
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to extract information and convert to other formats if required. The format
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described can be directly accepted as a layer by Poky using its standard
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layers mechanism, but it is important to recognise that the BSP captures all
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OpenEmbedded build systems.
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It is intended that this information can be
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used by other systems besides Poky and OpenEmbedded and thatspecified it will be simple
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to extract information and convert it to other formats if required.
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Poky, through its standard slyers mechanism, can directly accept The format
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described as a layer.
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The BSP captures all
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the hardware specific details in one place in a standard format, which is
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useful for any person wishing to use the hardware platform regardless of
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the build system in use.
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the build system being used.
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</para>
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<para>
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The BSP specification does not include a build system or other tools -
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it is concerned with the hardware specific components only. At the end
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distribution point the BSP may be shipped combined with a build system
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and other tools, but it is important to maintain the distinction that these
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are separate components which may just be combined in certain end products.
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it is concerned with the hardware-specific components only.
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At the end
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distribution point you can shipt the BSP combined with a build system
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and other tools.
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However, it is important to maintain the distinction that these
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are separate components that happen to be combined in certain end products.
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</para>
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<section id='bsp-filelayout'>
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<section id="bsp-filelayout">
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<title>Example Filesystem Layout</title>
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<para>
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The BSP consists of a file structure inside a base directory, meta-bsp in this example, where "bsp" is a placeholder for the machine or platform name. Examples of some files that it could contain are:
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The BSP consists of a file structure inside a base directory, meta-bsp in this example,
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where "bsp" is a placeholder for the machine or platform name.
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Examples of some files that it could contain are:
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</para>
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<para>
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@ -76,15 +83,18 @@ meta-bsp/prebuilds/
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</section>
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<section id='bsp-filelayout-binary'>
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<section id="bsp-filelayout-binary">
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<title>Prebuilt User Binaries (meta-bsp/binary/*)</title>
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<para>
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This optional area contains useful prebuilt kernels and userspace filesystem
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images appropriate to the target system. Users could use these to get a system
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running and quickly get started on development tasks. The exact types of binaries
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images appropriate to the target system.
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Users could use these to get a system
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running and quickly get started on development tasks.
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The exact types of binaries
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present will be highly hardware-dependent but a README file should be present
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explaining how to use them with the target hardware. If prebuilt binaries are
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explaining how to use them with the target hardware.
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If prebuilt binaries are
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present, source code to meet licensing requirements must also be provided in
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some form.
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</para>
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@ -95,9 +105,10 @@ meta-bsp/prebuilds/
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<title>Layer Configuration (meta-bsp/conf/layer.conf)</title>
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<para>
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This file identifies the structure as a Poky layer. This file identifies the
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contents of the layer and contains information about how Poky should use
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it. In general it will most likely be a standard boilerplate file consisting of:
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This file identifies the structure as a Poky layer by identifying the
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contents of the layer and containing information about how Poky should use
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it.
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Generally, a standard boilerplate file consisting of the following works.
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</para>
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<para>
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@ -106,7 +117,7 @@ meta-bsp/prebuilds/
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BBPATH := "${BBPATH}${LAYERDIR}"
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# We have a recipes directory containing .bb and .bbappend files, add to BBFILES
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BBFILES := "${BBFILES} ${LAYERDIR}/recipes/*/*.bb ${LAYERDIR}/recipes/*/*.bbappend"
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BBFILES := "${BBFILES} ${LAYERDIR}/recipes/*/*.bb \ ${LAYERDIR}/recipes/*/*.bbappend"
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BBFILE_COLLECTIONS += "bsp"
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BBFILE_PATTERN_bsp := "^${LAYERDIR}/"
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@ -115,47 +126,45 @@ BBFILE_PRIORITY_bsp = "5"
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</para>
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<para>
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which simply makes bitbake aware of the recipes and conf directories.
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</para>
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<para>
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This file is required for recognition of the BSP by Poky.
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This file simply makes bitbake aware of the recipes and conf directories and is required
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for recognition of the BSP by Poky.
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</para>
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</section>
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<section id='bsp-filelayout-machine'>
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<section id="bsp-filelayout-machine">
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<title>Hardware Configuration Options (meta-bsp/conf/machine/*.conf)</title>
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<para>
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The machine files bind together all the information contained elsewhere
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in the BSP into a format that Poky/OpenEmbedded can understand. If
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the BSP supports multiple machines, multiple machine configuration files
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can be present. These filenames correspond to the values users set the
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MACHINE variable to.
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in the BSP into a format that Poky/OpenEmbedded can understand.
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If the BSP supports multiple machines, multiple machine configuration files
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can be present.
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These filenames correspond to the values to which users have set the MACHINE variable.
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</para>
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<para>
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These files would define things like which kernel package to use
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(PREFERRED_PROVIDER of virtual/kernel), which hardware drivers to
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These files define things such as what kernel package to use
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(PREFERRED_PROVIDER of virtual/kernel), what hardware drivers to
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include in different types of images, any special software components
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that are needed, any bootloader information, and also any special image
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format requirements.
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</para>
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<para>
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At least one machine file is required for a Poky BSP layer but more than one may be present.
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At least one machine file is required for a Poky BSP layer.
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However, you can supply more than one file.
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</para>
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</section>
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<section id='bsp-filelayout-tune'>
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<title>Hardware Optimisation Options (meta-bsp/conf/machine/include/tune-*.inc)</title>
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<section id="bsp-filelayout-tune">
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<title>Hardware Optimization Options (meta-bsp/conf/machine/include/tune-*.inc)</title>
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<para>
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These are shared hardware "tuning" definitions and are commonly used to
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pass specific optimisation flags to the compiler. An example is
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tune-atom.inc:
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pass specific optimization flags to the compiler.
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An example is tune-atom.inc:
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</para>
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<para>
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<programlisting>
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@ -164,40 +173,42 @@ TARGET_CC_ARCH = "-m32 -march=core2 -msse3 -mtune=generic -mfpmath=sse"
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</programlisting>
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</para>
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<para>
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which defines a new package architecture called "core2" and uses the
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optimization flags specified, which are carefully chosen to give best
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performance on atom cpus.
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This example defines a new package architecture called "core2" and uses the
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specified optimization flags, which are carefully chosen to give best
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performance on atom processors.
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</para>
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<para>
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The tune file would be included by the machine definition and can be
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contained in the BSP or reference one from the standard core set of
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contained in the BSP or referenced from one of the standard core set of
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files included with Poky itself.
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</para>
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<para>
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These files are optional for a Poky BSP layer.
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Both the base package architecuture file and the tune file are optional for a Poky BSP layer.
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</para>
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</section>
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<section id='bsp-filelayout-kernel'>
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<title>Linux Kernel Configuration (meta-bsp/packages/linux/*)</title>
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<para>
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These files make up the definition of a kernel to use with this
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hardware. In this case it is a complete self-contained kernel with its own
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hardware.
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In this case it is a complete self-contained kernel with its own
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configuration and patches but kernels can be shared between many
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machines as well. Taking some specific example files:
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</para>
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<para>
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machines as well.
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Following is an example:
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<programlisting>
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meta-bsp/packages/linux/linux-bsp_2.6.50.bb
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</programlisting>
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This example file is the core kernel recipe that details from where to get the kernel
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source.
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All standard source code locations are supported so this could
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be a release tarball, some git repository, or source included in
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the directory within the BSP itself.
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</para>
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<para>
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which is the core kernel recipe which firstly details where to get the kernel
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source from. All standard source code locations are supported so this could
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be a release tarball, some git repository, or source included in
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the directory within the BSP itself. It then contains information about which
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patches to apply and how to configure and build it. It can reuse the main
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Poky kernel build class, so the definitions here can remain very simple.
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The file then contains information about what patches to apply and how to configure and build them.
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It can reuse the main Poky kernel build class, so the definitions here can remain very simple.
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</para>
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<para>
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<programlisting>
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@ -205,7 +216,7 @@ linux-bsp-2.6.50/*.patch
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</programlisting>
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</para>
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<para>
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which are patches which may be applied against the base kernel, wherever
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The above example file contains patches you can apply against the base kernel, wherever
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they may have been obtained from.
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</para>
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<para>
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@ -214,11 +225,11 @@ meta-bsp/packages/linux/linux-bsp-2.6.50/defconfig-bsp
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</programlisting>
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</para>
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<para>
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which is the configuration information to use to configure the kernel.
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Finally, this last example file contains configuration information to use to configure the kernel.
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</para>
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<para>
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Examples of kernel recipes are available in Poky itself. These files are
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optional since a kernel from Poky itself could be selected, although it
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Examples of kernel recipes are available in Poky itself.
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These files are optional since a kernel from Poky itself could be selected, although it
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would be unusual not to have a kernel configuration.
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</para>
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</section>
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|
@ -227,11 +238,19 @@ meta-bsp/packages/linux/linux-bsp-2.6.50/defconfig-bsp
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<title>Other Software (meta-bsp/packages/*)</title>
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<para>
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This area includes other pieces of software which the hardware may need for best
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operation. These are just examples of the kind of things that may be
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encountered. These are standard .bb file recipes in the usual Poky format,
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so for examples, see standard Poky recipes. The source can be included directly,
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referred to in source control systems or release tarballs of external software projects.
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This section describes other pieces of software that the hardware might need for best
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operation.
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These are examples of the kinds of things that you could encounter.
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The examples used in this section are standard <filename>.bb</filename> file recipes in the
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usual Poky format.
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You can include the source directly by referring to it in the source control system or
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the released tarballs of external software projects.
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You only need to provide these types of files if the platform requires them.
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</para>
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<para>
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The following file is a bootloader recipe that can be used to generate a new
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bootloader binary.
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Sometimes these files are included in the final image format and are needed to reflash hardware.
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</para>
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<para>
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<programlisting>
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|
@ -239,9 +258,9 @@ meta-bsp/packages/bootloader/bootloader_0.1.bb
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</programlisting>
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</para>
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<para>
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Some kind of bootloader recipe which may be used to generate a new
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bootloader binary. Sometimes these are included in the final image
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format and needed to reflash hardware.
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These next two files are examples of a hardware driver and a hardware daemon that might need
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to be included in images to make the hardware useful.
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Although the example uses "modem" there may be other components needed, such as firmware.
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</para>
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<para>
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<programlisting>
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|
@ -250,72 +269,62 @@ meta-bsp/packages/modem/modem-daemon_0.1.bb
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</programlisting>
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</para>
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<para>
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These are examples of a hardware driver and also a hardware daemon which
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may need to be included in images to make the hardware useful. "modem"
|
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is one example but there may be other components needed like firmware.
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Sometimes the device needs an image in a very specific format so that the update
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mechanism can accept and reflash it.
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Recipes to build the tools needed to do this can be included with the BSP.
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Following is an example.
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</para>
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<para>
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<programlisting>
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meta-bsp/packages/image-creator/image-creator-native_0.1.bb
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</programlisting>
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</para>
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<para>
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Sometimes the device will need an image in a very specific format for
|
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its update mechanism to accept and reflash with it. Recipes to build the
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tools needed to do this can be included with the BSP.
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</para>
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<para>
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These files only need be provided if the platform requires them.
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</para>
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</section>
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<section id='bs-filelayout-bbappend'>
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<title>Append BSP specific information to existing recipes</title>
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<title>Append BSP-Specific Information to Existing Recipes</title>
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<para>
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Say you have a recipe like pointercal which has machine-specific information in it,
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and then you have your new BSP code in a layer. Before the .bbappend extension was
|
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introduced, you'd have to copy the whole pointercal recipe and files into your layer,
|
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and then add the single file for your machine, which is ugly.
|
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|
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.bbappend makes the above work much easier, to allow BSP-specific information to be merged
|
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with the original recipe easily. When bitbake finds any X.bbappend files, they will be
|
||||
included after bitbake loads X.bb but before finalise or anonymous methods run.
|
||||
This allows the BSP layer to poke around and do whatever it might want to customise
|
||||
the original recipe.
|
||||
|
||||
If your recipe needs to reference extra files it can use the FILESEXTRAPATH variable
|
||||
to specify their location. The example below shows extra files contained in a folder
|
||||
called ${PN} (the package name).
|
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Suppose you have a recipe such as 'pointercal' that requires machine-specific information.
|
||||
At the same time, you have your new BSP code nicely partitioned into a layer, which is where
|
||||
you would also like to specify any machine-specific information associated with your new machine.
|
||||
Before the <filename>.bbappend</filename> extension was introduced, you would have to copy the whole
|
||||
pointercal recipe and files into your layer, and then add the single file for your machine.
|
||||
</para>
|
||||
<para>
|
||||
With the <filename>.bbappend</filename> extension, however, your work becomes much easier.
|
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It allows you to easily merge BSP-specific information with the original recipe.
|
||||
Whenever bitbake finds any <filename>.bbappend</filename> files, they will be
|
||||
included after bitbake loads the associated <filename>.bb</filename> but before any finalize
|
||||
or anonymous methods run.
|
||||
This allows the BSP layer to do whatever it might want to do to customize the original recipe.
|
||||
</para>
|
||||
<para>
|
||||
If your recipe needs to reference extra files it can use the FILESEXTRAPATH variable
|
||||
to specify their location.
|
||||
The example below shows extra files contained in a folder called ${PN} (the package name).
|
||||
</para>
|
||||
|
||||
<programlisting>
|
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FILESEXTRAPATHS := "${THISDIR}/${PN}"
|
||||
</programlisting>
|
||||
|
||||
<para>
|
||||
Then the BSP could add machine-specific config files in layer directory, which will be
|
||||
added by bitbake. You can look at meta-emenlow/packages/formfactor as an example.
|
||||
This technique allows the BSP to add machine-specific configuration files to the layer directory,
|
||||
which will be picked up by bitbake.
|
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For an example see <filename>meta-emenlow/packages/formfactor</filename>.
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</para>
|
||||
</section>
|
||||
|
||||
<section id='bsp-filelayout-prebuilds'>
|
||||
<section id="bsp-filelayout-prebuilds">
|
||||
<title>Prebuild Data (meta-bsp/prebuilds/*)</title>
|
||||
|
||||
<para>
|
||||
The location can contain a precompiled representation of the source code
|
||||
contained elsewhere in the BSP layer. It can be processed and used by
|
||||
Poky to provide much faster build times, assuming a compatible configuration is used.
|
||||
This location can contain precompiled representations of the source code
|
||||
contained elsewhere in the BSP layer.
|
||||
Assuming a compatible configuration is used, Poky can process and use these optional precompiled
|
||||
representations to provide much faster build times.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
These files are optional.
|
||||
</para>
|
||||
|
||||
</section>
|
||||
|
||||
<section id='bsp-click-through-licensing'>
|
||||
<title>BSP 'Click-through' Licensing Procedure</title>
|
||||
<title>BSP 'Click-Through' Licensing Procedure</title>
|
||||
|
||||
<note><para> This section is here as a description of how
|
||||
click-through licensing is expected to work, and is
|
||||
|
@ -367,10 +376,9 @@ FILESEXTRAPATHS := "${THISDIR}/${PN}"
|
|||
|
||||
<para>
|
||||
Get a license key (or keys) for the encumbered BSP
|
||||
by
|
||||
visiting <ulink url='https://pokylinux.org/bsp-keys.html'>https://pokylinux.org/bsp-keys.html</ulink>
|
||||
and give the web form there the name of the BSP
|
||||
and your e-mail address.
|
||||
by visiting
|
||||
<ulink url='https://pokylinux.org/bsp-keys.html'>https://pokylinux.org/bsp-keys.html</ulink>
|
||||
and give the web form there the name of the BSP and your e-mail address.
|
||||
</para>
|
||||
|
||||
<programlisting>
|
||||
|
|
Loading…
Reference in New Issue