documentation: dev-manual - Updates to configuring Kernel section
Eliminated the section A.2, which had an example of how to use menuconfig in the kerenl example appendix. The information is now merged into the similar section in Chapter 4 "Common Tasks." It was decided that the Appendix A examples in the manual were too detailed for a general development guide. (From yocto-docs rev: f88ec421b257657f02cc0f132ec2580c17f07cef) Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
This commit is contained in:
Scott Rifenbark
Richard Purdie
parent
d38325cbca
commit
274095d4c2
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@ -1352,6 +1352,8 @@
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<para>
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The easiest way to define kernel configurations is to set them through the
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<filename>menuconfig</filename> tool.
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This tool provides an interactive method with which
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to set kernel configurations.
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For general information on <filename>menuconfig</filename>, see
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<ulink url='http://en.wikipedia.org/wiki/Menuconfig'></ulink>.
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</para>
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@ -1359,6 +1361,9 @@
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<para>
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To use the <filename>menuconfig</filename> tool in the Yocto Project development
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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'>
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@ -1367,17 +1372,86 @@
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$ bitbake linux-yocto -c menuconfig
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</literallayout>
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Once <filename>menuconfig</filename> comes up, its standard interface allows you to
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examine and configure all the kernel configuration parameters.
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Once you have made your changes, simply exit the tool and save your changes 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.
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</para>
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<para>
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For an example that shows how to change a specific kernel option
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using <filename>menuconfig</filename>, see the
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"<link linkend='changing-the-config-smp-configuration-using-menuconfig'>Changing
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the <filename>CONFIG_SMP</filename> Configuration Using <filename>menuconfig</filename></link>"
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section.
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Consider an example that configures the <filename>linux-yocto-3.4</filename>
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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
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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>
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directory and then builds and launches <filename>menuconfig</filename>:
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<literallayout class='monospaced'>
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$ bitbake linux-yocto -c menuconfig
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</literallayout>
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</para>
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<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>.
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After highlighting the selection, you can use the arrow keys to select or deselect
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the setting.
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When you are finished with all your selections, exit out and save them.
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</para>
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<para>
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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
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kernel during the build.
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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
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Linux 3.4 kernel and you were building a QEMU image targeted for
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<filename>x86</filename> architecture, the
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<filename>.config</filename> file would be located here:
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<literallayout class='monospaced'>
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~/poky/build/tmp/work/qemux86-poky-linux/linux-yocto-3.4.11+git1+84f...
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...656ed30-r1/linux-qemux86-standard-build
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</literallayout>
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<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.
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</note>
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</para>
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<para>
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Within the <filename>.config</filename> file, you can see the kernel settings.
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For example, the following entry shows that symmetric multi-processor support
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is not set:
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<literallayout class='monospaced'>
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# CONFIG_SMP is not set
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</literallayout>
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</para>
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<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
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as many changes an you want and save them, then compare the renamed configuration
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file against the newly created file.
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You can use the resulting differences as your base to create configuration fragments
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to permanently save in your kernel layer.
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<note>
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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>
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from which to work.
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</note>
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</para>
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</section>
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@ -546,299 +546,6 @@
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</para>
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</section>
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</section>
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<section id='changing-the-kernel-configuration'>
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<title>Changing the Kernel Configuration</title>
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<para>
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This example changes the default behavior, which is "on", of the Symmetric
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Multi-processing Support (<filename>CONFIG_SMP</filename>) to "off".
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It is a simple example that demonstrates how to reconfigure the kernel.
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</para>
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<section id='getting-set-up-to-run-this-example'>
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<title>Getting Set Up to Run this Example</title>
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<para>
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If you took the time to work through the example that modifies the kernel source code
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in "<link linkend='modifying-the-kernel-source-code'>Modifying the Kernel Source
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Code</link>" you should already have the Source Directory set up on your
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host machine.
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If this is the case, go to the next section, which is titled
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"<link linkend='examining-the-default-config-smp-behavior'>Examining the Default
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<filename>CONFIG_SMP</filename> Behavior</link>", and continue with the
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example.
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</para>
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<para>
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If you don't have the Source Directory established on your system,
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you can get them through tarball extraction or by
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cloning the <filename>poky</filename> Git repository.
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This example uses <filename>poky</filename> as the root directory of the
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<link linkend='source-directory'>Source Directory</link>.
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See the bulleted item
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"<link linkend='local-yp-release'>Yocto Project Release</link>"
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for information on how to get these files.
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</para>
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<para>
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Once you have the local copy of the repository set up,
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you have many development branches from which you can work.
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From inside the repository you can see the branch names and the tag names used
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in the upstream Git repository using either of the following commands:
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<literallayout class='monospaced'>
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$ cd poky
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$ git branch -a
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$ git tag -l
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</literallayout>
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This example uses the Yocto Project &DISTRO; Release code named "&DISTRO_NAME;",
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which maps to the <filename>&DISTRO_NAME;</filename> branch in the repository.
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The following commands create and checkout the local <filename>&DISTRO_NAME;</filename>
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branch:
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<literallayout class='monospaced'>
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$ git checkout -b &DISTRO_NAME; origin/&DISTRO_NAME;
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Branch &DISTRO_NAME; set up to track remote branch &DISTRO_NAME; from origin.
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Switched to a new branch '&DISTRO_NAME;'
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</literallayout>
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</para>
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<para>
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Next, you need to build the default <filename>qemux86</filename> image that you
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can boot using QEMU.
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<note>
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Because a full build can take hours, you should check two variables in the
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<filename>build</filename> directory that is created after you source the
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<filename>&OE_INIT_FILE;</filename> script.
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You can find these variables
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<filename>BB_NUMBER_THREADS</filename> and <filename>PARALLEL_MAKE</filename>
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in the <filename>build/conf</filename> directory in the
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<filename>local.conf</filename> configuration file.
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By default, these variables are commented out.
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If your host development system supports multi-core and multi-thread capabilities,
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you can uncomment these statements and set the variables to significantly shorten
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the full build time.
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As a guideline, set both the <filename>BB_NUMBER_THREADS</filename> and the
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<filename>PARALLEL_MAKE</filename> variables to twice the number
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of cores your machine supports.
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</note>
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The following two commands <filename>source</filename> the build environment setup script
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and build the default <filename>qemux86</filename> image.
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If necessary, the script creates the build directory:
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<literallayout class='monospaced'>
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$ cd ~/poky
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$ source &OE_INIT_FILE;
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### Shell environment set up for builds. ###
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You can now run 'bitbake <target>'
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Common targets are:
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core-image-minimal
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core-image-sato
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meta-toolchain
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meta-toolchain-sdk
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adt-installer
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meta-ide-support
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You can also run generated qemu images with a command like 'runqemu qemux86'
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</literallayout>
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</para>
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<para>
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The following <filename>bitbake</filename> command starts the build:
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<literallayout class='monospaced'>
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$ bitbake -k core-image-minimal
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</literallayout>
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<note>Be sure to check the settings in the <filename>local.conf</filename>
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before starting the build.</note>
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</para>
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</section>
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<section id='examining-the-default-config-smp-behavior'>
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<title>Examining the Default <filename>CONFIG_SMP</filename> Behavior</title>
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<para>
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By default, <filename>CONFIG_SMP</filename> supports multiple processor machines.
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To see this default setting from within the QEMU emulator, boot your image using
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the emulator as follows:
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<literallayout class='monospaced'>
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$ runqemu qemux86 qemuparams="-smp 4"
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</literallayout>
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</para>
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<para>
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Login to the machine using <filename>root</filename> with no password.
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After logging in, enter the following command to see how many processors are
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being supported in the emulator.
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The emulator reports support for the number of processors you specified using
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the <filename>-smp</filename> option, four in this case:
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<literallayout class='monospaced'>
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# cat /proc/cpuinfo | grep processor
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processor : 0
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processor : 1
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processor : 2
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processor : 3
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#
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</literallayout>
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To check the setting for <filename>CONFIG_SMP</filename>, you can use the
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following command:
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<literallayout class='monospaced'>
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zcat /proc/config.gz | grep CONFIG_SMP
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</literallayout>
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The console returns the following showing that multi-processor machine support
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is set:
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<literallayout class='monospaced'>
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CONFIG_SMP=y
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</literallayout>
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Logout of the emulator using the <filename>exit</filename> command and
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then close it down.
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</para>
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</section>
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<section id='changing-the-config-smp-configuration-using-menuconfig'>
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<title>Changing the <filename>CONFIG_SMP</filename> Configuration Using <filename>menuconfig</filename></title>
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<para>
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The <filename>menuconfig</filename> tool provides an interactive method with which
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to set kernel configurations.
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You need to run <filename>menuconfig</filename> inside the Yocto BitBake environment.
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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 build directory.
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If you have not sourced this script do so with the following commands:
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<literallayout class='monospaced'>
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$ cd ~/poky
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$ source &OE_INIT_FILE;
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</literallayout>
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</para>
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<para>
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After setting up the environment to run <filename>menuconfig</filename>, you are ready
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to use the tool to interactively change the kernel configuration.
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In this example, we are basing our changes on the <filename>linux-yocto-3.4</filename>
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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
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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>
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directory and then builds and launches <filename>menuconfig</filename>:
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<literallayout class='monospaced'>
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$ bitbake linux-yocto -c menuconfig
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</literallayout>
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</para>
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<para>
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Once <filename>menuconfig</filename> launches, navigate through the user interface
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to find the <filename>CONFIG_SMP</filename> configuration setting.
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You can find it at <filename>Processor Type and Features</filename>.
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The configuration selection is
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<filename>Symmetric Multi-processing Support</filename>.
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After using the arrow keys to highlight this selection, press "n" to turn it off.
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Then, exit out and save your selections.
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</para>
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<para>
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Once you save the selection, the <filename>.config</filename> configuration file
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is updated.
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This is the file that the build system uses to configure the Yocto Project kernel
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when it is built.
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You can find and examine this file in the build directory.
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This example uses the following:
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<literallayout class='monospaced'>
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~/poky/build/tmp/work/qemux86-poky-linux/linux-yocto-3.4.11+git1+84f...
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...656ed30-r1/linux-qemux86-standard-build
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</literallayout>
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<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 might differ
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slightly.
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</note>
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</para>
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<para>
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Within the <filename>.config</filename> file, you can see the following setting:
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<literallayout class='monospaced'>
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# CONFIG_SMP is not set
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</literallayout>
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</para>
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<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
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as many changes an you want and save them, then compare the renamed configuration
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||||
file against the newly created file.
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You can use the resulting differences as your base to create configuration fragments
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to permanently save in your kernel layer.
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<note>
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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>
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from which to work.
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</note>
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</para>
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</section>
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<section id='recompiling-the-kernel-and-testing-the-new-configuration'>
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<title>Recompiling the Kernel and Testing the New Configuration</title>
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<para>
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At this point, you are ready to recompile your kernel image with
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the new setting in effect using the BitBake command below:
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<literallayout class='monospaced'>
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$ bitbake linux-yocto
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</literallayout>
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</para>
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<para>
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Now run the QEMU emulator and pass it the same multi-processor option as before:
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<literallayout class='monospaced'>
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$ runqemu qemux86 qemuparams="-smp 4"
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</literallayout>
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</para>
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<para>
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Login to the machine using <filename>root</filename> with no password
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and test for the number of processors the kernel supports:
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<literallayout class='monospaced'>
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# cat /proc/cpuinfo | grep processor
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processor : 0
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#
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</literallayout>
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</para>
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<para>
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From the output, you can see that the kernel no longer supports multi-processor systems.
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The output indicates support for a single processor. You can verify the
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<filename>CONFIG_SMP</filename> setting by using this command:
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<literallayout class='monospaced'>
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zcat /proc/config.gz | grep CONFIG_SMP
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</literallayout>
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The console returns the following output:
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<literallayout class='monospaced'>
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# CONFIG_SMP is not set
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</literallayout>
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You have successfully reconfigured the kernel.
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</para>
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</section>
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</section>
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<section id='adding-kernel-recipes'>
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<title>Adding Kernel Recipes</title>
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<para>
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A future release of this manual will present an example that adds kernel recipes, which provide
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new functionality to the kernel.
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</para>
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<para>
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<imagedata fileref="figures/wip.png"
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width="2in" depth="3in" align="center" scalefit="1" />
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</para>
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</section>
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</appendix>
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<!--
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