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ed0d609c7c
Fixes [YOCTO #10946] There was insufficient information in the combination of the BSP Guide and the Kernel Development Manual on just how to locate and use kernel metadata. * bsp-guide - Removed the detailed append file example for the kernel recipe. This is moved now to the chapter in the kernel manual that describes append files. * kernel-dev - Placed the example from the BSP Guide into the section that describes kernel append files. Cleaned up some terminology issues throughout chapter 3. Added information about how BitBake picks up kernel metadata when the metadata is in a hierarchical directory and not just a simple *.scc file. (From yocto-docs rev: 1048acb7127e77ca9c1f524a208fe25344fcb57c) Signed-off-by: Scott Rifenbark <srifenbark@gmail.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
1322 lines
67 KiB
XML
1322 lines
67 KiB
XML
<!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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[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
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<chapter id='kernel-dev-common'>
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<title>Common Tasks</title>
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<para>
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This chapter presents several common tasks you perform when you
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work with the Yocto Project Linux kernel.
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These tasks include preparing a layer, modifying an existing recipe,
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iterative development, working with your own sources, and incorporating
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out-of-tree modules.
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<note>
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The examples presented in this chapter work with the Yocto Project
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1.2.2 Release and forward.
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</note>
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</para>
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<section id='creating-and-preparing-a-layer'>
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<title>Creating and Preparing a Layer</title>
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<para>
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If you are going to be modifying kernel recipes, it is recommended
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that you create and prepare your own layer in which to do your
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work.
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Your layer contains its own
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<ulink url='&YOCTO_DOCS_DEV_URL;#bitbake-term'>BitBake</ulink>
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append files
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(<filename>.bbappend</filename>) and provides a convenient
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mechanism to create your own recipe files
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(<filename>.bb</filename>).
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For details on how to create and work with layers, see the following
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sections in the Yocto Project Development Manual:
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<itemizedlist>
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<listitem><para>"<ulink url='&YOCTO_DOCS_DEV_URL;#understanding-and-creating-layers'>Understanding and Creating Layers</ulink>" for
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general information on layers and how to create layers.</para></listitem>
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<listitem><para>"<ulink url='&YOCTO_DOCS_DEV_URL;#set-up-your-layer-for-the-build'>Set Up Your Layer for the Build</ulink>" for
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specific instructions on setting up a layer for kernel
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development.</para></listitem>
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</itemizedlist>
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</para>
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</section>
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<section id='modifying-an-existing-recipe'>
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<title>Modifying an Existing Recipe</title>
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<para>
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In many cases, you can customize an existing linux-yocto recipe to
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meet the needs of your project.
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Each release of the Yocto Project provides a few Linux
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kernel recipes from which you can choose.
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These are located in the
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<ulink url='&YOCTO_DOCS_DEV_URL;#source-directory'>Source Directory</ulink>
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in <filename>meta/recipes-kernel/linux</filename>.
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</para>
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<para>
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Modifying an existing recipe can consist of the following:
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<itemizedlist>
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<listitem><para>Creating the append file</para></listitem>
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<listitem><para>Applying patches</para></listitem>
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<listitem><para>Changing the configuration</para></listitem>
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</itemizedlist>
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</para>
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<para>
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Before modifying an existing recipe, be sure that you have created
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a minimal, custom layer from which you can work.
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See the "<link linkend='creating-and-preparing-a-layer'>Creating and Preparing a Layer</link>"
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section for some general resources.
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You can also see the
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"<ulink url='&YOCTO_DOCS_DEV_URL;#set-up-your-layer-for-the-build'>Set Up Your Layer for the Build</ulink>" section
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of the Yocto Project Development Manual for a detailed
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example.
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</para>
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<section id='creating-the-append-file'>
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<title>Creating the Append File</title>
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<para>
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You create this file in your custom layer.
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You also name it accordingly based on the linux-yocto recipe
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you are using.
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For example, if you are modifying the
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<filename>meta/recipes-kernel/linux/linux-yocto_4.4.bb</filename>
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recipe, the append file will typically be located as follows
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within your custom layer:
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<literallayout class='monospaced'>
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<replaceable>your-layer</replaceable>/recipes-kernel/linux/linux-yocto_4.4.bbappend
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</literallayout>
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The append file should initially extend the
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<ulink url='&YOCTO_DOCS_REF_URL;#var-FILESPATH'><filename>FILESPATH</filename></ulink>
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search path by prepending the directory that contains your
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files to the
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<ulink url='&YOCTO_DOCS_REF_URL;#var-FILESEXTRAPATHS'><filename>FILESEXTRAPATHS</filename></ulink>
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variable as follows:
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<literallayout class='monospaced'>
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FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
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</literallayout>
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The path <filename>${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-THISDIR'><filename>THISDIR</filename></ulink><filename>}/${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-PN'><filename>PN</filename></ulink><filename>}</filename>
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expands to "linux-yocto" in the current directory for this
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example.
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If you add any new files that modify the kernel recipe and you
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have extended <filename>FILESPATH</filename> as
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described above, you must place the files in your layer in the
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following area:
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<literallayout class='monospaced'>
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<replaceable>your-layer</replaceable>/recipes-kernel/linux/linux-yocto/
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</literallayout>
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<note>If you are working on a new machine Board Support Package
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(BSP), be sure to refer to the
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<ulink url='&YOCTO_DOCS_BSP_URL;'>Yocto Project Board Support Package (BSP) Developer's Guide</ulink>.
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</note>
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</para>
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<para>
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As an example, consider the following append file
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used by the BSPs in <filename>meta-yocto-bsp</filename>:
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<literallayout class='monospaced'>
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meta-yocto-bsp/recipes-kernel/linux/linux-yocto_4.4.bbappend
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</literallayout>
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The following listing shows the file.
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Be aware that the actual commit ID strings in this
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example listing might be different than the actual strings
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in the file from the <filename>meta-yocto-bsp</filename>
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layer upstream.
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<literallayout class='monospaced'>
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KBRANCH_genericx86 = "standard/base"
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KBRANCH_genericx86-64 = "standard/base"
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KMACHINE_genericx86 ?= "common-pc"
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KMACHINE_genericx86-64 ?= "common-pc-64"
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KBRANCH_edgerouter = "standard/edgerouter"
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KBRANCH_beaglebone = "standard/beaglebone"
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KBRANCH_mpc8315e-rdb = "standard/fsl-mpc8315e-rdb"
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SRCREV_machine_genericx86 ?= "ad8b1d659ddd2699ebf7d50ef9de8940b157bfc2"
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SRCREV_machine_genericx86-64 ?= "ad8b1d659ddd2699ebf7d50ef9de8940b157bfc2"
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SRCREV_machine_edgerouter ?= "cebe1ad56aebd89e0de29412e19433fb441bf13c"
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SRCREV_machine_beaglebone ?= "cebe1ad56aebd89e0de29412e19433fb441bf13c"
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SRCREV_machine_mpc8315e-rdb ?= "06c0dbdcba374ca7f92a53d69292d6bb7bc9b0f3"
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COMPATIBLE_MACHINE_genericx86 = "genericx86"
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COMPATIBLE_MACHINE_genericx86-64 = "genericx86-64"
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COMPATIBLE_MACHINE_edgerouter = "edgerouter"
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COMPATIBLE_MACHINE_beaglebone = "beaglebone"
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COMPATIBLE_MACHINE_mpc8315e-rdb = "mpc8315e-rdb"
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LINUX_VERSION_genericx86 = "4.4.41"
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LINUX_VERSION_genericx86-64 = "4.4.41"
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LINUX_VERSION_edgerouter = "4.4.53"
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LINUX_VERSION_beaglebone = "4.4.53"
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LINUX_VERSION_mpc8315e-rdb = "4.4.53"
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</literallayout>
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This append file contains statements used to support
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several BSPs that ship with the Yocto Project.
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The file defines machines using the
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<ulink url='&YOCTO_DOCS_REF_URL;#var-COMPATIBLE_MACHINE'><filename>COMPATIBLE_MACHINE</filename></ulink>
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variable and uses the
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<ulink url='&YOCTO_DOCS_REF_URL;#var-KMACHINE'><filename>KMACHINE</filename></ulink>
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variable to ensure the machine name used by the OpenEmbedded
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build system maps to the machine name used by the Linux Yocto
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kernel.
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The file also uses the optional
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<ulink url='&YOCTO_DOCS_REF_URL;#var-KBRANCH'><filename>KBRANCH</filename></ulink>
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variable to ensure the build process uses the
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appropriate kernel branch.
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</para>
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<para>
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Although this particular example does not use it, the
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<ulink url='&YOCTO_DOCS_REF_URL;#var-KERNEL_FEATURES'><filename>KERNEL_FEATURES</filename></ulink>
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variable could be used to enable features specific to
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the kernel.
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The append file points to specific commits in the
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<ulink url='&YOCTO_DOCS_DEV_URL;#source-directory'>Source Directory</ulink>
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Git repository and the <filename>meta</filename> Git repository
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branches to identify the exact kernel needed to build the
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BSP.
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</para>
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<para>
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One thing missing in this particular BSP, which you will
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typically need when developing a BSP, is the kernel configuration
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file (<filename>.config</filename>) for your BSP.
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When developing a BSP, you probably have a kernel configuration
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file or a set of kernel configuration files that, when taken
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together, define the kernel configuration for your BSP.
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You can accomplish this definition by putting the configurations
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in a file or a set of files inside a directory located at the
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same level as your kernel's append file and having the same
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name as the kernel's main recipe file.
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With all these conditions met, simply reference those files in the
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<ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink>
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statement in the append file.
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</para>
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<para>
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For example, suppose you had some configuration options
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in a file called <filename>network_configs.cfg</filename>.
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You can place that file inside a directory named
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<filename>linux-yocto</filename> and then add
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a <filename>SRC_URI</filename> statement such as the
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following to the append file.
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When the OpenEmbedded build system builds the kernel, the
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configuration options are picked up and applied.
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<literallayout class='monospaced'>
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SRC_URI += "file://network_configs.cfg"
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</literallayout>
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</para>
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<para>
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To group related configurations into multiple files, you
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perform a similar procedure.
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Here is an example that groups separate configurations
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specifically for Ethernet and graphics into their own
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files and adds the configurations by using a
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<filename>SRC_URI</filename> statement like the following
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in your append file:
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<literallayout class='monospaced'>
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SRC_URI += "file://myconfig.cfg \
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file://eth.cfg \
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file://gfx.cfg"
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</literallayout>
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</para>
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<para>
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Another variable you can use in your kernel recipe append
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file is the
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<ulink url='&YOCTO_DOCS_REF_URL;#var-FILESEXTRAPATHS'><filename>FILESEXTRAPATHS</filename></ulink>
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variable.
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When you use this statement, you are extending the locations
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used by the OpenEmbedded system to look for files and
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patches as the recipe is processed.
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</para>
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<note>
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<para>
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Other methods exist to accomplish grouping and defining configuration options.
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For example, if you are working with a local clone of the kernel repository,
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you could checkout the kernel's <filename>meta</filename> branch, make your changes,
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and then push the changes to the local bare clone of the kernel.
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The result is that you directly add configuration options to the
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<filename>meta</filename> branch for your BSP.
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The configuration options will likely end up in that location anyway if the BSP gets
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added to the Yocto Project.
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</para>
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<para>
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In general, however, the Yocto Project maintainers take care of moving the
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<filename>SRC_URI</filename>-specified
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configuration options to the kernel's <filename>meta</filename> branch.
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Not only is it easier for BSP developers to not have to worry about putting those
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configurations in the branch, but having the maintainers do it allows them to apply
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'global' knowledge about the kinds of common configuration options multiple BSPs in
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the tree are typically using.
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This allows for promotion of common configurations into common features.
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</para>
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</note>
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</section>
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<section id='applying-patches'>
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<title>Applying Patches</title>
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<para>
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If you have a single patch or a small series of patches
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that you want to apply to the Linux kernel source, you
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can do so just as you would with any other recipe.
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You first copy the patches to the path added to
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<ulink url='&YOCTO_DOCS_REF_URL;#var-FILESEXTRAPATHS'><filename>FILESEXTRAPATHS</filename></ulink>
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in your <filename>.bbappend</filename> file as described in
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the previous section, and then reference them in
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<ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink>
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statements.
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</para>
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<para>
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For example, you can apply a three-patch series by adding the
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following lines to your linux-yocto
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<filename>.bbappend</filename> file in your layer:
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<literallayout class='monospaced'>
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SRC_URI += "file://0001-first-change.patch"
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SRC_URI += "file://0002-second-change.patch"
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SRC_URI += "file://0003-third-change.patch"
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</literallayout>
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The next time you run BitBake to build the Linux kernel,
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BitBake detects the change in the recipe and fetches and
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applies the patches before building the kernel.
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</para>
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<para>
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For a detailed example showing how to patch the kernel, see the
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"<ulink url='&YOCTO_DOCS_DEV_URL;#patching-the-kernel'>Patching the Kernel</ulink>"
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section in the Yocto Project Development Manual.
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</para>
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</section>
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<section id='changing-the-configuration'>
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<title>Changing the Configuration</title>
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<para>
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You can make wholesale or incremental changes to the final
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<filename>.config</filename> file used for the eventual
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Linux kernel configuration by including a
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<filename>defconfig</filename> file and by specifying
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configuration fragments in the
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<ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink>
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to be applied to that file.
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</para>
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<para>
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If you have a complete, working Linux kernel
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<filename>.config</filename>
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file you want to use for the configuration, as before, copy
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that file to the appropriate <filename>${PN}</filename>
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directory in your layer's
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<filename>recipes-kernel/linux</filename> directory,
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and rename the copied file to "defconfig".
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Then, add the following lines to the linux-yocto
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<filename>.bbappend</filename> file in your layer:
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<literallayout class='monospaced'>
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FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
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SRC_URI += "file://defconfig"
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</literallayout>
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The <filename>SRC_URI</filename> tells the build system how to
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search for the file, while the
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<ulink url='&YOCTO_DOCS_REF_URL;#var-FILESEXTRAPATHS'><filename>FILESEXTRAPATHS</filename></ulink>
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extends the
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<ulink url='&YOCTO_DOCS_REF_URL;#var-FILESPATH'><filename>FILESPATH</filename></ulink>
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variable (search directories) to include the
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<filename>${PN}</filename> directory you created to hold the
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configuration changes.
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</para>
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<note>
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The build system applies the configurations from the
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<filename>defconfig</filename> file before applying any
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subsequent configuration fragments.
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The final kernel configuration is a combination of the
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configurations in the <filename>defconfig</filename> file and
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any configuration fragments you provide.
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You need to realize that if you have any configuration
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fragments, the build system applies these on top of and
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after applying the existing <filename>defconfig</filename>
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file configurations.
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</note>
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<para>
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Generally speaking, the preferred approach is to determine the
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incremental change you want to make and add that as a
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configuration fragment.
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For example, if you want to add support for a basic serial
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console, create a file named <filename>8250.cfg</filename> in
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the <filename>${PN}</filename> directory with the following
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content (without indentation):
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<literallayout class='monospaced'>
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CONFIG_SERIAL_8250=y
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CONFIG_SERIAL_8250_CONSOLE=y
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CONFIG_SERIAL_8250_PCI=y
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CONFIG_SERIAL_8250_NR_UARTS=4
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CONFIG_SERIAL_8250_RUNTIME_UARTS=4
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CONFIG_SERIAL_CORE=y
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CONFIG_SERIAL_CORE_CONSOLE=y
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</literallayout>
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Next, include this configuration fragment and extend the
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<filename>FILESPATH</filename> variable in your
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<filename>.bbappend</filename> file:
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<literallayout class='monospaced'>
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FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
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SRC_URI += "file://8250.cfg"
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</literallayout>
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The next time you run BitBake to build the Linux kernel, BitBake
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detects the change in the recipe and fetches and applies the
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new configuration before building the kernel.
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</para>
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<para>
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For a detailed example showing how to configure the kernel,
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see the
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"<ulink url='&YOCTO_DOCS_DEV_URL;#configuring-the-kernel'>Configuring the Kernel</ulink>"
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section in the Yocto Project Development Manual.
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</para>
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</section>
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|
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<section id='using-an-in-tree-defconfig-file'>
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<title>Using an "In-Tree" <filename>defconfig</filename> File</title>
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<para>
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It might be desirable to have kernel configuration fragment
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support through a <filename>defconfig</filename> file that
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is pulled from the kernel source tree for the configured
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machine.
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By default, the OpenEmbedded build system looks for
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<filename>defconfig</filename> files in the layer used for
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Metadata, which is "out-of-tree", and then configures them
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using the following:
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<literallayout class='monospaced'>
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SRC_URI += "file://defconfig"
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</literallayout>
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If you do not want to maintain copies of
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<filename>defconfig</filename> files in your layer but would
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rather allow users to use the default configuration from the
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kernel tree and still be able to add configuration fragments
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to the
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<ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink>
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through, for example, append files, you can direct the
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OpenEmbedded build system to use a
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<filename>defconfig</filename> file that is "in-tree".
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</para>
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<para>
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To specify an "in-tree" <filename>defconfig</filename> file,
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edit the recipe that builds your kernel so that it has the
|
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following command form:
|
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<literallayout class='monospaced'>
|
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KBUILD_DEFCONFIG_KMACHINE ?= <replaceable>defconfig_file</replaceable>
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</literallayout>
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You need to append the variable with
|
|
<ulink url='&YOCTO_DOCS_REF_URL;#var-KMACHINE'><filename>KMACHINE</filename></ulink>
|
|
and then supply the path to your "in-tree"
|
|
<filename>defconfig</filename> file.
|
|
</para>
|
|
|
|
<para>
|
|
Aside from modifying your kernel recipe and providing your own
|
|
<filename>defconfig</filename> file, you need to be sure no
|
|
files or statements set <filename>SRC_URI</filename> to use a
|
|
<filename>defconfig</filename> other than your "in-tree"
|
|
file (e.g. a kernel's <filename>linux-</filename><replaceable>machine</replaceable><filename>.inc</filename>
|
|
file).
|
|
In other words, if the build system detects a statement
|
|
that identifies an "out-of-tree"
|
|
<filename>defconfig</filename> file, that statement
|
|
will override your
|
|
<filename>KBUILD_DEFCONFIG</filename> variable.
|
|
</para>
|
|
|
|
<para>
|
|
See the
|
|
<ulink url='&YOCTO_DOCS_REF_URL;#var-KBUILD_DEFCONFIG'><filename>KBUILD_DEFCONFIG</filename></ulink>
|
|
variable description for more information.
|
|
</para>
|
|
</section>
|
|
</section>
|
|
|
|
<section id='using-an-iterative-development-process'>
|
|
<title>Using an Iterative Development Process</title>
|
|
|
|
<para>
|
|
If you do not have existing patches or configuration files,
|
|
you can iteratively generate them from within the BitBake build
|
|
environment as described within this section.
|
|
During an iterative workflow, running a previously completed BitBake
|
|
task causes BitBake to invalidate the tasks that follow the
|
|
completed task in the build sequence.
|
|
Invalidated tasks rebuild the next time you run the build using
|
|
BitBake.
|
|
</para>
|
|
|
|
<para>
|
|
As you read this section, be sure to substitute the name
|
|
of your Linux kernel recipe for the term
|
|
"linux-yocto".
|
|
</para>
|
|
|
|
<section id='tip-dirty-string'>
|
|
<title>"-dirty" String</title>
|
|
|
|
<!--
|
|
<para>
|
|
<emphasis>AR - Darren Hart:</emphasis> This section
|
|
originated from the old Yocto Project Kernel Architecture
|
|
and Use Manual.
|
|
It was decided we need to put it in this section here.
|
|
Darren needs to figure out where we want it and what part
|
|
of it we want (all, revision???)
|
|
</para>
|
|
-->
|
|
|
|
<para>
|
|
If kernel images are being built with "-dirty" on the
|
|
end of the version string, this simply means that
|
|
modifications in the source directory have not been committed.
|
|
<literallayout class='monospaced'>
|
|
$ git status
|
|
</literallayout>
|
|
</para>
|
|
|
|
<para>
|
|
You can use the above Git command to report modified,
|
|
removed, or added files.
|
|
You should commit those changes to the tree regardless of
|
|
whether they will be saved, exported, or used.
|
|
Once you commit the changes, you need to rebuild the kernel.
|
|
</para>
|
|
|
|
<para>
|
|
To force a pickup and commit of all such pending changes,
|
|
enter the following:
|
|
<literallayout class='monospaced'>
|
|
$ git add .
|
|
$ git commit -s -a -m "getting rid of -dirty"
|
|
</literallayout>
|
|
</para>
|
|
|
|
<para>
|
|
Next, rebuild the kernel.
|
|
</para>
|
|
</section>
|
|
|
|
<section id='generating-configuration-files'>
|
|
<title>Generating Configuration Files</title>
|
|
|
|
<para>
|
|
You can manipulate the <filename>.config</filename> file
|
|
used to build a linux-yocto recipe with the
|
|
<filename>menuconfig</filename> command as follows:
|
|
<literallayout class='monospaced'>
|
|
$ bitbake linux-yocto -c menuconfig
|
|
</literallayout>
|
|
This command starts the Linux kernel configuration tool,
|
|
which allows you to prepare a new
|
|
<filename>.config</filename> file for the build.
|
|
When you exit the tool, be sure to save your changes
|
|
at the prompt.
|
|
</para>
|
|
|
|
<para>
|
|
The resulting <filename>.config</filename> file is
|
|
located in the build directory,
|
|
<filename>${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-B'><filename>B</filename></ulink><filename>}</filename>,
|
|
which expands to
|
|
<filename>${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-WORKDIR'><filename>WORKDIR</filename></ulink><filename>}</filename><filename>/linux-</filename><filename>${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-PACKAGE_ARCH'><filename>PACKAGE_ARCH</filename></ulink><filename>}-${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-LINUX_KERNEL_TYPE'><filename>LINUX_KERNEL_TYPE</filename></ulink><filename>}-build</filename>.
|
|
You can use the entire <filename>.config</filename> file as the
|
|
<filename>defconfig</filename> file as described in the
|
|
"<link linkend='changing-the-configuration'>Changing the Configuration</link>" section.
|
|
For more information on the <filename>.config</filename> file,
|
|
see the
|
|
"<ulink url='&YOCTO_DOCS_DEV_URL;#using-menuconfig'>Using <filename>menuconfig</filename></ulink>"
|
|
section in the Yocto Project Development Manual.
|
|
<note>
|
|
You can determine what a variable expands to by looking
|
|
at the output of the <filename>bitbake -e</filename>
|
|
command:
|
|
<literallayout class='monospaced'>
|
|
$ bitbake -e virtual/kernel
|
|
</literallayout>
|
|
Search the output for the variable in which you are
|
|
interested to see exactly how it is expanded and used.
|
|
</note>
|
|
</para>
|
|
|
|
<para>
|
|
A better method is to create a configuration fragment using the
|
|
differences between two configuration files: one previously
|
|
created and saved, and one freshly created using the
|
|
<filename>menuconfig</filename> tool.
|
|
</para>
|
|
|
|
<para>
|
|
To create a configuration fragment using this method, follow
|
|
these steps:
|
|
<orderedlist>
|
|
<listitem><para>Complete a build at least through the kernel
|
|
configuration task as follows:
|
|
<literallayout class='monospaced'>
|
|
$ bitbake linux-yocto -c kernel_configme -f
|
|
</literallayout>
|
|
This step ensures that you will be creating a
|
|
<filename>.config</filename> file from a known state.
|
|
Because situations exist where your build state might
|
|
become unknown, it is best to run the previous
|
|
command prior to starting up
|
|
<filename>menuconfig</filename>.
|
|
</para></listitem>
|
|
<listitem><para>Run the <filename>menuconfig</filename>
|
|
command:
|
|
<literallayout class='monospaced'>
|
|
$ bitbake linux-yocto -c menuconfig
|
|
</literallayout></para></listitem>
|
|
<listitem><para>Run the <filename>diffconfig</filename>
|
|
command to prepare a configuration fragment.
|
|
The resulting file <filename>fragment.cfg</filename>
|
|
will be placed in the
|
|
<filename>${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-WORKDIR'><filename>WORKDIR</filename></ulink><filename>}</filename> directory:
|
|
<literallayout class='monospaced'>
|
|
$ bitbake linux-yocto -c diffconfig
|
|
</literallayout></para></listitem>
|
|
</orderedlist>
|
|
</para>
|
|
|
|
<para>
|
|
The <filename>diffconfig</filename> command creates a file that is a
|
|
list of Linux kernel <filename>CONFIG_</filename> assignments.
|
|
See the "<link linkend='changing-the-configuration'>Changing the Configuration</link>"
|
|
section for information on how to use the output as a
|
|
configuration fragment.
|
|
<note>
|
|
You can also use this method to create configuration
|
|
fragments for a BSP.
|
|
See the "<link linkend='bsp-descriptions'>BSP Descriptions</link>"
|
|
section for more information.
|
|
</note>
|
|
</para>
|
|
|
|
<para>
|
|
The kernel tools also provide configuration validation.
|
|
You can use these tools to produce warnings for when a
|
|
requested configuration does not appear in the final
|
|
<filename>.config</filename> file or when you override a
|
|
policy configuration in a hardware configuration fragment.
|
|
Here is an example with some sample output of the command
|
|
that runs these tools:
|
|
<literallayout class='monospaced'>
|
|
$ bitbake linux-yocto -c kernel_configcheck -f
|
|
|
|
...
|
|
|
|
NOTE: validating kernel configuration
|
|
This BSP sets 3 invalid/obsolete kernel options.
|
|
These config options are not offered anywhere within this kernel.
|
|
The full list can be found in your kernel src dir at:
|
|
meta/cfg/standard/mybsp/invalid.cfg
|
|
|
|
This BSP sets 21 kernel options that are possibly non-hardware related.
|
|
The full list can be found in your kernel src dir at:
|
|
meta/cfg/standard/mybsp/specified_non_hdw.cfg
|
|
|
|
WARNING: There were 2 hardware options requested that do not
|
|
have a corresponding value present in the final ".config" file.
|
|
This probably means you are not getting the config you wanted.
|
|
The full list can be found in your kernel src dir at:
|
|
meta/cfg/standard/mybsp/mismatch.cfg
|
|
</literallayout>
|
|
</para>
|
|
|
|
<para>
|
|
The output describes the various problems that you can
|
|
encounter along with where to find the offending configuration
|
|
items.
|
|
You can use the information in the logs to adjust your
|
|
configuration files and then repeat the
|
|
<filename>kernel_configme</filename> and
|
|
<filename>kernel_configcheck</filename> commands until
|
|
they produce no warnings.
|
|
</para>
|
|
|
|
<para>
|
|
For more information on how to use the
|
|
<filename>menuconfig</filename> tool, see the
|
|
"<ulink url='&YOCTO_DOCS_DEV_URL;#using-menuconfig'>Using <filename>menuconfig</filename></ulink>"
|
|
section in the Yocto Project Development Manual.
|
|
</para>
|
|
</section>
|
|
|
|
<section id='modifying-source-code'>
|
|
<title>Modifying Source Code</title>
|
|
|
|
<para>
|
|
You can experiment with source code changes and create a
|
|
simple patch without leaving the BitBake environment.
|
|
To get started, be sure to complete a build at
|
|
least through the kernel configuration task:
|
|
<literallayout class='monospaced'>
|
|
$ bitbake linux-yocto -c kernel_configme -f
|
|
</literallayout>
|
|
Taking this step ensures you have the sources prepared
|
|
and the configuration completed.
|
|
You can find the sources in the build directory within the
|
|
<filename>source/</filename> directory, which is a symlink
|
|
(i.e. <filename>${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-B'><filename>B</filename></ulink><filename>}/source</filename>).
|
|
The <filename>source/</filename> directory expands to
|
|
<filename>${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-WORKDIR'><filename>WORKDIR</filename></ulink><filename>}</filename><filename>/linux-</filename><filename>${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-PACKAGE_ARCH'><filename>PACKAGE_ARCH</filename></ulink><filename>}-${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-LINUX_KERNEL_TYPE'><filename>LINUX_KERNEL_TYPE</filename></ulink><filename>}-build/source</filename>.
|
|
The directory pointed to by the
|
|
<filename>source/</filename> symlink is also known as
|
|
<filename>${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-STAGING_KERNEL_DIR'><filename>STAGING_KERNEL_DIR</filename></ulink><filename>}</filename>.
|
|
</para>
|
|
|
|
<para>
|
|
You can edit the sources as you would any other Linux source
|
|
tree.
|
|
However, keep in mind that you will lose changes if you
|
|
trigger the
|
|
<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-fetch'><filename>do_fetch</filename></ulink>
|
|
task for the recipe.
|
|
You can avoid triggering this task by not using BitBake to
|
|
run the
|
|
<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-cleanall'><filename>cleanall</filename></ulink>,
|
|
<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-cleansstate'><filename>cleansstate</filename></ulink>,
|
|
or forced
|
|
<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-fetch'><filename>fetch</filename></ulink>
|
|
commands.
|
|
Also, do not modify the recipe itself while working
|
|
with temporary changes or BitBake might run the
|
|
<filename>fetch</filename> command depending on the
|
|
changes to the recipe.
|
|
</para>
|
|
|
|
<para>
|
|
To test your temporary changes, instruct BitBake to run the
|
|
<filename>compile</filename> again.
|
|
The <filename>-f</filename> option forces the command to run
|
|
even though BitBake might think it has already done so:
|
|
<literallayout class='monospaced'>
|
|
$ bitbake linux-yocto -c compile -f
|
|
</literallayout>
|
|
If the compile fails, you can update the sources and repeat
|
|
the <filename>compile</filename>.
|
|
Once compilation is successful, you can inspect and test
|
|
the resulting build (i.e. kernel, modules, and so forth) from
|
|
the following build directory:
|
|
<literallayout class='monospaced'>
|
|
${WORKDIR}/linux-${PACKAGE_ARCH}-${LINUX_KERNEL_TYPE}-build
|
|
</literallayout>
|
|
Alternatively, you can run the <filename>deploy</filename>
|
|
command to place the kernel image in the
|
|
<filename>tmp/deploy/images</filename> directory:
|
|
<literallayout class='monospaced'>
|
|
$ bitbake linux-yocto -c deploy
|
|
</literallayout>
|
|
And, of course, you can perform the remaining installation and
|
|
packaging steps by issuing:
|
|
<literallayout class='monospaced'>
|
|
$ bitbake linux-yocto
|
|
</literallayout>
|
|
</para>
|
|
|
|
<para>
|
|
For rapid iterative development, the edit-compile-repeat loop
|
|
described in this section is preferable to rebuilding the
|
|
entire recipe because the installation and packaging tasks
|
|
are very time consuming.
|
|
</para>
|
|
|
|
<para>
|
|
Once you are satisfied with your source code modifications,
|
|
you can make them permanent by generating patches and
|
|
applying them to the
|
|
<ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink>
|
|
statement as described in the
|
|
"<link linkend='applying-patches'>Applying Patches</link>"
|
|
section.
|
|
If you are not familiar with generating patches, refer to the
|
|
"<ulink url='&YOCTO_DOCS_DEV_URL;#creating-the-patch'>Creating the Patch</ulink>"
|
|
section in the Yocto Project Development Manual.
|
|
</para>
|
|
</section>
|
|
</section>
|
|
|
|
<section id='working-with-your-own-sources'>
|
|
<title>Working With Your Own Sources</title>
|
|
|
|
<para>
|
|
If you cannot work with one of the Linux kernel
|
|
versions supported by existing linux-yocto recipes, you can
|
|
still make use of the Yocto Project Linux kernel tooling by
|
|
working with your own sources.
|
|
When you use your own sources, you will not be able to
|
|
leverage the existing kernel
|
|
<ulink url='&YOCTO_DOCS_DEV_URL;#metadata'>Metadata</ulink> and
|
|
stabilization work of the linux-yocto sources.
|
|
However, you will be able to manage your own Metadata in the same
|
|
format as the linux-yocto sources.
|
|
Maintaining format compatibility facilitates converging with
|
|
linux-yocto on a future, mutually-supported kernel version.
|
|
</para>
|
|
|
|
<para>
|
|
To help you use your own sources, the Yocto Project provides a
|
|
linux-yocto custom recipe
|
|
(<filename>linux-yocto-custom.bb</filename>) that uses
|
|
<filename>kernel.org</filename> sources
|
|
and the Yocto Project Linux kernel tools for managing
|
|
kernel Metadata.
|
|
You can find this recipe in the
|
|
<filename>poky</filename> Git repository of the
|
|
Yocto Project <ulink url='&YOCTO_GIT_URL;'>Source Repository</ulink>
|
|
at:
|
|
<literallayout class="monospaced">
|
|
poky/meta-skeleton/recipes-kernel/linux/linux-yocto-custom.bb
|
|
</literallayout>
|
|
</para>
|
|
|
|
<para>
|
|
Here are some basic steps you can use to work with your own sources:
|
|
<orderedlist>
|
|
<listitem><para>Copy the <filename>linux-yocto-custom.bb</filename>
|
|
recipe to your layer and give it a meaningful name.
|
|
The name should include the version of the Linux kernel you
|
|
are using (e.g.
|
|
<filename>linux-yocto-myproject_3.19.bb</filename>,
|
|
where "3.19" is the base version of the Linux kernel
|
|
with which you would be working).</para></listitem>
|
|
<listitem><para>In the same directory inside your layer,
|
|
create a matching directory
|
|
to store your patches and configuration files (e.g.
|
|
<filename>linux-yocto-myproject</filename>).
|
|
</para></listitem>
|
|
<listitem><para>Make sure you have either a
|
|
<filename>defconfig</filename> file or configuration
|
|
fragment files.
|
|
When you use the <filename>linux-yocto-custom.bb</filename>
|
|
recipe, you must specify a configuration.
|
|
If you do not have a <filename>defconfig</filename> file,
|
|
you can run the following:
|
|
<literallayout class='monospaced'>
|
|
$ make defconfig
|
|
</literallayout>
|
|
After running the command, copy the resulting
|
|
<filename>.config</filename> to the
|
|
<filename>files</filename> directory as "defconfig" and
|
|
then add it to the
|
|
<ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink>
|
|
variable in the recipe.</para>
|
|
<para>Running the <filename>make defconfig</filename>
|
|
command results in the default configuration for your
|
|
architecture as defined by your kernel.
|
|
However, no guarantee exists that this configuration is
|
|
valid for your use case, or that your board will even boot.
|
|
This is particularly true for non-x86 architectures.
|
|
To use non-x86 <filename>defconfig</filename> files, you
|
|
need to be more specific and find one that matches your
|
|
board (i.e. for arm, you look in
|
|
<filename>arch/arm/configs</filename> and use the one that
|
|
is the best starting point for your board).
|
|
</para></listitem>
|
|
<listitem><para>Edit the following variables in your recipe
|
|
as appropriate for your project:
|
|
<itemizedlist>
|
|
<listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink>:
|
|
The <filename>SRC_URI</filename> should specify
|
|
a Git repository that uses one of the supported Git
|
|
fetcher protocols (i.e. <filename>file</filename>,
|
|
<filename>git</filename>, <filename>http</filename>,
|
|
and so forth).
|
|
The <filename>SRC_URI</filename> variable should
|
|
also specify either a <filename>defconfig</filename>
|
|
file or some configuration fragment files.
|
|
The skeleton recipe provides an example
|
|
<filename>SRC_URI</filename> as a syntax reference.
|
|
</para></listitem>
|
|
<listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-LINUX_VERSION'><filename>LINUX_VERSION</filename></ulink>:
|
|
The Linux kernel version you are using (e.g.
|
|
"3.19").</para></listitem>
|
|
<listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-LINUX_VERSION_EXTENSION'><filename>LINUX_VERSION_EXTENSION</filename></ulink>:
|
|
The Linux kernel <filename>CONFIG_LOCALVERSION</filename>
|
|
that is compiled into the resulting kernel and visible
|
|
through the <filename>uname</filename> command.
|
|
</para></listitem>
|
|
<listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-SRCREV'><filename>SRCREV</filename></ulink>:
|
|
The commit ID from which you want to build.
|
|
</para></listitem>
|
|
<listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-PR'><filename>PR</filename></ulink>:
|
|
Treat this variable the same as you would in any other
|
|
recipe.
|
|
Increment the variable to indicate to the OpenEmbedded
|
|
build system that the recipe has changed.
|
|
</para></listitem>
|
|
<listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-PV'><filename>PV</filename></ulink>:
|
|
The default <filename>PV</filename> assignment is
|
|
typically adequate.
|
|
It combines the <filename>LINUX_VERSION</filename>
|
|
with the Source Control Manager (SCM) revision
|
|
as derived from the
|
|
<ulink url='&YOCTO_DOCS_REF_URL;#var-SRCPV'><filename>SRCPV</filename></ulink>
|
|
variable.
|
|
The combined results are a string with
|
|
the following form:
|
|
<literallayout class='monospaced'>
|
|
3.19.11+git1+68a635bf8dfb64b02263c1ac80c948647cc76d5f_1+218bd8d2022b9852c60d32f0d770931e3cf343e2
|
|
</literallayout>
|
|
While lengthy, the extra verbosity in <filename>PV</filename>
|
|
helps ensure you are using the exact
|
|
sources from which you intend to build.
|
|
</para></listitem>
|
|
<listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-COMPATIBLE_MACHINE'><filename>COMPATIBLE_MACHINE</filename></ulink>:
|
|
A list of the machines supported by your new recipe.
|
|
This variable in the example recipe is set
|
|
by default to a regular expression that matches
|
|
only the empty string, "(^$)".
|
|
This default setting triggers an explicit build
|
|
failure.
|
|
You must change it to match a list of the machines
|
|
that your new recipe supports.
|
|
For example, to support the <filename>qemux86</filename>
|
|
and <filename>qemux86-64</filename> machines, use
|
|
the following form:
|
|
<literallayout class='monospaced'>
|
|
COMPATIBLE_MACHINE = "qemux86|qemux86-64"
|
|
</literallayout></para></listitem>
|
|
</itemizedlist></para></listitem>
|
|
<listitem><para>Provide further customizations to your recipe
|
|
as needed just as you would customize an existing
|
|
linux-yocto recipe.
|
|
See the "<link linkend='modifying-an-existing-recipe'>Modifying
|
|
an Existing Recipe</link>" section for information.
|
|
</para></listitem>
|
|
</orderedlist>
|
|
</para>
|
|
</section>
|
|
|
|
<section id='working-with-out-of-tree-modules'>
|
|
<title>Working with Out-of-Tree Modules</title>
|
|
|
|
<para>
|
|
This section describes steps to build out-of-tree modules on
|
|
your target and describes how to incorporate out-of-tree modules
|
|
in the build.
|
|
</para>
|
|
|
|
<section id='building-out-of-tree-modules-on-the-target'>
|
|
<title>Building Out-of-Tree Modules on the Target</title>
|
|
|
|
<para>
|
|
While the traditional Yocto Project development model would be
|
|
to include kernel modules as part of the normal build
|
|
process, you might find it useful to build modules on the
|
|
target.
|
|
This could be the case if your target system is capable
|
|
and powerful enough to handle the necessary compilation.
|
|
Before deciding to build on your target, however, you should
|
|
consider the benefits of using a proper cross-development
|
|
environment from your build host.
|
|
</para>
|
|
|
|
<para>
|
|
If you want to be able to build out-of-tree modules on
|
|
the target, there are some steps you need to take
|
|
on the target that is running your SDK image.
|
|
Briefly, the <filename>kernel-dev</filename> package
|
|
is installed by default on all
|
|
<filename>*.sdk</filename> images and the
|
|
<filename>kernel-devsrc</filename> package is installed
|
|
on many of the <filename>*.sdk</filename> images.
|
|
However, you need to create some scripts prior to
|
|
attempting to build the out-of-tree modules on the target
|
|
that is running that image.
|
|
</para>
|
|
|
|
<para>
|
|
Prior to attempting to build the out-of-tree modules,
|
|
you need to be on the target as root and you need to
|
|
change to the <filename>/usr/src/kernel</filename> directory.
|
|
Next, <filename>make</filename> the scripts:
|
|
<literallayout class='monospaced'>
|
|
# cd /usr/src/kernel
|
|
# make scripts
|
|
</literallayout>
|
|
Because all SDK image recipes include
|
|
<filename>dev-pkgs</filename>, the
|
|
<filename>kernel-dev</filename> packages will be installed
|
|
as part of the SDK image and the
|
|
<filename>kernel-devsrc</filename> packages will be installed
|
|
as part of applicable SDK images.
|
|
The SDK uses the scripts when building out-of-tree
|
|
modules.
|
|
Once you have switched to that directory and created the
|
|
scripts, you should be able to build your out-of-tree modules
|
|
on the target.
|
|
</para>
|
|
</section>
|
|
|
|
<section id='incorporating-out-of-tree-modules'>
|
|
<title>Incorporating Out-of-Tree Modules</title>
|
|
|
|
<para>
|
|
While it is always preferable to work with sources integrated
|
|
into the Linux kernel sources, if you need an external kernel
|
|
module, the <filename>hello-mod.bb</filename> recipe is
|
|
available as a template from which you can create your
|
|
own out-of-tree Linux kernel module recipe.
|
|
</para>
|
|
|
|
<para>
|
|
This template recipe is located in the
|
|
<filename>poky</filename> Git repository of the
|
|
Yocto Project <ulink url='&YOCTO_GIT_URL;'>Source Repository</ulink>
|
|
at:
|
|
<literallayout class="monospaced">
|
|
poky/meta-skeleton/recipes-kernel/hello-mod/hello-mod_0.1.bb
|
|
</literallayout>
|
|
</para>
|
|
|
|
<para>
|
|
To get started, copy this recipe to your layer and give it a
|
|
meaningful name (e.g. <filename>mymodule_1.0.bb</filename>).
|
|
In the same directory, create a new directory named
|
|
<filename>files</filename> where you can store any source files,
|
|
patches, or other files necessary for building
|
|
the module that do not come with the sources.
|
|
Finally, update the recipe as needed for the module.
|
|
Typically, you will need to set the following variables:
|
|
<itemizedlist>
|
|
<listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-DESCRIPTION'><filename>DESCRIPTION</filename></ulink>
|
|
</para></listitem>
|
|
<listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-LICENSE'><filename>LICENSE*</filename></ulink>
|
|
</para></listitem>
|
|
<listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink>
|
|
</para></listitem>
|
|
<listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-PV'><filename>PV</filename></ulink>
|
|
</para></listitem>
|
|
</itemizedlist>
|
|
</para>
|
|
|
|
<para>
|
|
Depending on the build system used by the module sources,
|
|
you might need to make some adjustments.
|
|
For example, a typical module <filename>Makefile</filename>
|
|
looks much like the one provided with the
|
|
<filename>hello-mod</filename> template:
|
|
<literallayout class='monospaced'>
|
|
obj-m := hello.o
|
|
|
|
SRC := $(shell pwd)
|
|
|
|
all:
|
|
$(MAKE) -C $(KERNEL_SRC) M=$(SRC)
|
|
|
|
modules_install:
|
|
$(MAKE) -C $(KERNEL_SRC) M=$(SRC) modules_install
|
|
...
|
|
</literallayout>
|
|
</para>
|
|
|
|
<para>
|
|
The important point to note here is the
|
|
<ulink url='&YOCTO_DOCS_REF_URL;#var-KERNEL_SRC'><filename>KERNEL_SRC</filename></ulink>
|
|
variable.
|
|
The
|
|
<ulink url='&YOCTO_DOCS_REF_URL;#ref-classes-module'><filename>module</filename></ulink>
|
|
class sets this variable and the
|
|
<ulink url='&YOCTO_DOCS_REF_URL;#var-KERNEL_PATH'><filename>KERNEL_PATH</filename></ulink>
|
|
variable to
|
|
<filename>${<ulink url='&YOCTO_DOCS_REF_URL;#var-STAGING_KERNEL_DIR'><filename>STAGING_KERNEL_DIR</filename></ulink>}</filename>
|
|
with the necessary Linux kernel build information to build
|
|
modules.
|
|
If your module <filename>Makefile</filename> uses a different
|
|
variable, you might want to override the
|
|
<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-compile'><filename>do_compile()</filename></ulink>
|
|
step, or create a patch to
|
|
the <filename>Makefile</filename> to work with the more typical
|
|
<filename>KERNEL_SRC</filename> or
|
|
<filename>KERNEL_PATH</filename> variables.
|
|
</para>
|
|
|
|
<para>
|
|
After you have prepared your recipe, you will likely want to
|
|
include the module in your images.
|
|
To do this, see the documentation for the following variables in
|
|
the Yocto Project Reference Manual and set one of them
|
|
appropriately for your machine configuration file:
|
|
<itemizedlist>
|
|
<listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE_ESSENTIAL_EXTRA_RDEPENDS'><filename>MACHINE_ESSENTIAL_EXTRA_RDEPENDS</filename></ulink>
|
|
</para></listitem>
|
|
<listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS'><filename>MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS</filename></ulink>
|
|
</para></listitem>
|
|
<listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE_EXTRA_RDEPENDS'><filename>MACHINE_EXTRA_RDEPENDS</filename></ulink>
|
|
</para></listitem>
|
|
<listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE_EXTRA_RRECOMMENDS'><filename>MACHINE_EXTRA_RRECOMMENDS</filename></ulink>
|
|
</para></listitem>
|
|
</itemizedlist>
|
|
</para>
|
|
|
|
<para>
|
|
Modules are often not required for boot and can be excluded from
|
|
certain build configurations.
|
|
The following allows for the most flexibility:
|
|
<literallayout class='monospaced'>
|
|
MACHINE_EXTRA_RRECOMMENDS += "kernel-module-mymodule"
|
|
</literallayout>
|
|
The value is derived by appending the module filename without
|
|
the <filename>.ko</filename> extension to the string
|
|
"kernel-module-".
|
|
</para>
|
|
|
|
<para>
|
|
Because the variable is
|
|
<ulink url='&YOCTO_DOCS_REF_URL;#var-RRECOMMENDS'><filename>RRECOMMENDS</filename></ulink>
|
|
and not a
|
|
<ulink url='&YOCTO_DOCS_REF_URL;#var-RDEPENDS'><filename>RDEPENDS</filename></ulink>
|
|
variable, the build will not fail if this module is not
|
|
available to include in the image.
|
|
</para>
|
|
</section>
|
|
</section>
|
|
|
|
|
|
<section id='inspecting-changes-and-commits'>
|
|
<title>Inspecting Changes and Commits</title>
|
|
|
|
<para>
|
|
A common question when working with a kernel is:
|
|
"What changes have been applied to this tree?"
|
|
Rather than using "grep" across directories to see what has
|
|
changed, you can use Git to inspect or search the kernel tree.
|
|
Using Git is an efficient way to see what has changed in the tree.
|
|
</para>
|
|
|
|
<section id='what-changed-in-a-kernel'>
|
|
<title>What Changed in a Kernel?</title>
|
|
|
|
<para>
|
|
Following are a few examples that show how to use Git
|
|
commands to examine changes.
|
|
These examples are by no means the only way to see changes.
|
|
<note>
|
|
In the following examples, unless you provide a commit
|
|
range, <filename>kernel.org</filename> history is blended
|
|
with Yocto Project kernel changes.
|
|
You can form ranges by using branch names from the
|
|
kernel tree as the upper and lower commit markers with
|
|
the Git commands.
|
|
You can see the branch names through the web interface
|
|
to the Yocto Project source repositories at
|
|
<ulink url='http://git.yoctoproject.org/cgit.cgi'></ulink>.
|
|
</note>
|
|
To see a full range of the changes, use the
|
|
<filename>git whatchanged</filename> command and specify a
|
|
commit range for the branch
|
|
(<replaceable>commit</replaceable><filename>..</filename><replaceable>commit</replaceable>).
|
|
</para>
|
|
|
|
<para>
|
|
Here is an example that looks at what has changed in the
|
|
<filename>emenlow</filename> branch of the
|
|
<filename>linux-yocto-3.19</filename> kernel.
|
|
The lower commit range is the commit associated with the
|
|
<filename>standard/base</filename> branch, while
|
|
the upper commit range is the commit associated with the
|
|
<filename>standard/emenlow</filename> branch.
|
|
<literallayout class='monospaced'>
|
|
$ git whatchanged origin/standard/base..origin/standard/emenlow
|
|
</literallayout>
|
|
</para>
|
|
|
|
<para>
|
|
To see short, one line summaries of changes use the
|
|
<filename>git log</filename> command:
|
|
<literallayout class='monospaced'>
|
|
$ git log --oneline origin/standard/base..origin/standard/emenlow
|
|
</literallayout>
|
|
</para>
|
|
|
|
<para>
|
|
Use this command to see code differences for the changes:
|
|
<literallayout class='monospaced'>
|
|
$ git diff origin/standard/base..origin/standard/emenlow
|
|
</literallayout>
|
|
</para>
|
|
|
|
<para>
|
|
Use this command to see the commit log messages and the
|
|
text differences:
|
|
<literallayout class='monospaced'>
|
|
$ git show origin/standard/base..origin/standard/emenlow
|
|
</literallayout>
|
|
</para>
|
|
|
|
<para>
|
|
Use this command to create individual patches for
|
|
each change.
|
|
Here is an example that that creates patch files for each
|
|
commit and places them in your <filename>Documents</filename>
|
|
directory:
|
|
<literallayout class='monospaced'>
|
|
$ git format-patch -o $HOME/Documents origin/standard/base..origin/standard/emenlow
|
|
</literallayout>
|
|
</para>
|
|
</section>
|
|
|
|
<section id='showing-a-particular-feature-or-branch-change'>
|
|
<title>Showing a Particular Feature or Branch Change</title>
|
|
|
|
<para>
|
|
Tags in the Yocto Project kernel tree divide changes for
|
|
significant features or branches.
|
|
The <filename>git show</filename> <replaceable>tag</replaceable>
|
|
command shows changes based on a tag.
|
|
Here is an example that shows <filename>systemtap</filename>
|
|
changes:
|
|
<literallayout class='monospaced'>
|
|
$ git show systemtap
|
|
</literallayout>
|
|
You can use the
|
|
<filename>git branch --contains</filename> <replaceable>tag</replaceable>
|
|
command to show the branches that contain a particular feature.
|
|
This command shows the branches that contain the
|
|
<filename>systemtap</filename> feature:
|
|
<literallayout class='monospaced'>
|
|
$ git branch --contains systemtap
|
|
</literallayout>
|
|
</para>
|
|
</section>
|
|
</section>
|
|
|
|
<section id='adding-recipe-space-kernel-features'>
|
|
<title>Adding Recipe-Space Kernel Features</title>
|
|
|
|
<para>
|
|
You can add kernel features in the
|
|
<link linkend='recipe-space-metadata'>recipe-space</link> by
|
|
using the
|
|
<ulink url='&YOCTO_DOCS_REF_URL;#var-KERNEL_FEATURES'><filename>KERNEL_FEATURES</filename></ulink>
|
|
variable and by specifying the feature's <filename>.scc</filename>
|
|
file path in the
|
|
<ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink>
|
|
statement.
|
|
When you add features using this method, the OpenEmbedded build
|
|
system checks to be sure the features are present.
|
|
If the features are not present, the build stops.
|
|
Kernel features are the last elements processed for configuring
|
|
and patching the kernel.
|
|
Therefore, adding features in this manner is a way
|
|
to enforce specific features are present and enabled
|
|
without needing to do a full audit of any other layer's additions
|
|
to the <filename>SRC_URI</filename> statement.
|
|
</para>
|
|
|
|
<para>
|
|
You add a kernel feature by providing the feature as part of the
|
|
<filename>KERNEL_FEATURES</filename> variable and by providing the
|
|
path to the feature's <filename>.scc</filename> file, which is
|
|
relative to the root of the kernel Metadata.
|
|
The OpenEmbedded build system searches all forms of kernel
|
|
Metadata on the <filename>SRC_URI</filename> statement regardless
|
|
of whether the Metadata is in the "kernel-cache", system kernel
|
|
Metadata, or a recipe-space Metadata.
|
|
See the
|
|
"<link linkend='kernel-metadata-location'>Kernel Metadata Location</link>"
|
|
section for additional information.
|
|
</para>
|
|
|
|
<para>
|
|
When you specify the feature's <filename>.scc</filename> file
|
|
on the <filename>SRC_URI</filename> statement, the OpenEmbedded
|
|
build system adds the directory of that
|
|
<filename>.scc</filename> file along with all its subdirectories
|
|
to the kernel feature search path.
|
|
Because subdirectories are searched, you can reference a single
|
|
<filename>.scc</filename> file in the
|
|
<filename>SRC_URI</filename> statement to reference multiple kernel
|
|
features.
|
|
</para>
|
|
|
|
<para>
|
|
Consider the following example that adds the "test.scc" feature
|
|
to the build.
|
|
<orderedlist>
|
|
<listitem><para>
|
|
Create a <filename>.scc</filename> file and locate it
|
|
just as you would any other patch file,
|
|
<filename>.cfg</filename> file, or fetcher item
|
|
you specify in the <filename>SRC_URI</filename>
|
|
statement.
|
|
<note><title>Notes</title>
|
|
<itemizedlist>
|
|
<listitem><para>
|
|
You must add the directory of the
|
|
<filename>.scc</filename> file to the fetcher's
|
|
search path in the same manner as you would
|
|
add a <filename>.patch</filename> file.
|
|
</para></listitem>
|
|
<listitem><para>
|
|
You can create additional
|
|
<filename>.scc</filename> files beneath the
|
|
directory that contains the file you are
|
|
adding.
|
|
All subdirectories are searched during the
|
|
build as potential feature directories.
|
|
</para></listitem>
|
|
</itemizedlist>
|
|
</note>
|
|
Continuing with the example, suppose the "test.scc"
|
|
feature you are adding has a
|
|
<filename>test.scc</filename> file in the following
|
|
directory:
|
|
<literallayout class='monospaced'>
|
|
<replaceable>my_recipe</replaceable>
|
|
|
|
|
+-linux-yocto
|
|
|
|
|
+-test.cfg
|
|
+-test.scc
|
|
</literallayout>
|
|
In this example, the <filename>linux-yocto</filename>
|
|
directory has both the feature
|
|
<filename>test.scc</filename> file and a similarly
|
|
named configuration fragment file
|
|
<filename>test.cfg</filename>.
|
|
</para></listitem>
|
|
<listitem><para>
|
|
Add the <filename>.scc</filename> file to the
|
|
recipe's <filename>SRC_URI</filename> statement:
|
|
<literallayout class='monospaced'>
|
|
SRC_URI_append = " file://test.scc"
|
|
</literallayout>
|
|
The leading space before the path is important as the
|
|
path is appended to the existing path.
|
|
</para></listitem>
|
|
<listitem><para>
|
|
Specify the feature as a kernel feature:
|
|
<literallayout class='monospaced'>
|
|
KERNEL_FEATURES_append = " test.scc"
|
|
</literallayout>
|
|
The OpenEmbedded build system processes the kernel feature
|
|
when it builds the kernel.
|
|
<note>
|
|
If other features are contained below "test.scc",
|
|
then their directories are relative to the directory
|
|
containing the <filename>test.scc</filename> file.
|
|
</note>
|
|
</para></listitem>
|
|
</orderedlist>
|
|
</para>
|
|
</section>
|
|
</chapter>
|
|
<!--
|
|
vim: expandtab tw=80 ts=4
|
|
-->
|