import-layers/yocto-poky/documentation/kernel-dev/kernel-dev-intro.xml - openbmc/openbmc - Gitiles

 <!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
 [<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >

 <chapter id='kernel-dev-intro'>
 <title>Introduction</title>

 <!--
 <para>
     <emphasis>AR - Darren Hart:</emphasis>  See if the concepts in these
     three bullets are adequately covered in somewhere in this manual:
     <itemizedlist>
         <listitem><para>Do we convey that our kernel Git repositories
             have a clear and continuous history, similar to the way the
             kernel Git repositories for <filename>kernel.org</filename>
             do.
             </para></listitem>
         <listitem><para>Does the manual note that Yocto Project delivers
             a key set of supported kernel types, where
             each type is tailored to meet a specific use (e.g. networking,
             consumer, devices, and so forth).</para></listitem>
         <listitem><para>Do we convey that the Yocto Project uses a
             Git branching strategy that, from a
             developer's point of view, results in a linear path from the
             baseline kernel.org, through a select group of features and
             ends with their BSP-specific commits.</para></listitem>
     </itemizedlist>
 </para>
 -->

     <section id='kernel-dev-overview'>
         <title>Overview</title>

         <para>
             Regardless of how you intend to make use of the Yocto Project,
             chances are you will work with the Linux kernel.
             This manual provides background information on the Yocto Linux kernel
             <ulink url='&YOCTO_DOCS_DEV_URL;#metadata'>Metadata</ulink>,
             describes common tasks you can perform using the kernel tools,
             and shows you how to use the kernel Metadata needed to work with
             the kernel inside the Yocto Project.
        </para>

        <para>
             Each Yocto Project release has a set of linux-yocto recipes, whose
             Git repositories you can view in the Yocto
             <ulink url='&YOCTO_GIT_URL;'>Source Repositories</ulink> under
             the "Yocto Linux Kernel" heading.
             New recipes for the release track the latest upstream developments
             and introduce newly-supported platforms.
             Previous recipes in the release are refreshed and supported for at
             least one additional release.
             As they align, these previous releases are updated to include the
             latest from the
             <ulink url='&YOCTO_HOME_URL;/organization/long-term-support-initiative-ltsi'>Long Term Support Initiative</ulink>
             (LTSI) project.
             Also included is a linux-yocto development recipe
             (<filename>linux-yocto-dev.bb</filename>) should you want to work
             with the very latest in upstream Linux kernel development and
             kernel Metadata development.
         </para>

         <para>
             The Yocto Project also provides a powerful set of kernel
             tools for managing Linux kernel sources and configuration data.
             You can use these tools to make a single configuration change,
             apply multiple patches, or work with your own kernel sources.
         </para>

         <para>
             In particular, the kernel tools allow you to generate configuration
             fragments that specify only what you must, and nothing more.
             Configuration fragments only need to contain the highest level
             visible <filename>CONFIG</filename> options as presented by the Linux
             kernel <filename>menuconfig</filename> system.
             Contrast this against a complete Linux kernel
             <filename>.config</filename>, which includes all the automatically
             selected <filename>CONFIG</filename> options.
             This efficiency reduces your maintenance effort and allows you
             to further separate your configuration in ways that make sense for
             your project.
             A common split separates policy and hardware.
             For example, all your kernels might support
             the <filename>proc</filename> and <filename>sys</filename> filesystems,
             but only specific boards require sound, USB, or specific drivers.
             Specifying these configurations individually allows you to aggregate
             them together as needed, but maintains them in only one place.
             Similar logic applies to separating source changes.
         </para>

         <para>
             If you do not maintain your own kernel sources and need to make
             only minimal changes to the sources, the released recipes provide a
             vetted base upon which to layer your changes.
             Doing so allows you to benefit from the continual kernel
             integration and testing performed during development of the
             Yocto Project.
         </para>

         <para>
             If, instead, you have a very specific Linux kernel source tree
             and are unable to align with one of the official linux-yocto
             recipes, an alternative exists by which you can use the Yocto
             Project Linux kernel tools with your own kernel sources.
         </para>
     </section>

     <section id='kernel-dev-other-resources'>
         <title>Other Resources</title>

         <para>
             The sections that follow provide instructions for completing
             specific Linux kernel development tasks.
             These instructions assume you are comfortable working with
             <ulink url='http://openembedded.org/wiki/Bitbake'>BitBake</ulink>
             recipes and basic open-source development tools.
             Understanding these concepts will facilitate the process of working
             with the kernel recipes.
             If you find you need some additional background, please be sure to
             review and understand the following documentation:
             <itemizedlist>
                 <listitem><para><ulink url='&YOCTO_DOCS_QS_URL;'>Yocto Project Quick Start</ulink>
                     </para></listitem>
                 <listitem><para>The "<ulink url='&YOCTO_DOCS_DEV_URL;#dev-modifying-source-code'>Modifying Source Code</ulink>"
                     section in the Yocto Project Development Manual
                     </para></listitem>
                 <listitem><para>The "<ulink url='&YOCTO_DOCS_DEV_URL;#understanding-and-creating-layers'>Understanding and Creating Layers</ulink>" section
                     in the Yocto Project Development Manual</para></listitem>
                 <listitem><para>The "<ulink url='&YOCTO_DOCS_DEV_URL;#modifying-the-kernel'>Modifying the Kernel</ulink>" section
                     in the Yocto Project Development Manual.</para></listitem>
             </itemizedlist>
         </para>

         <para>
             Finally, while this document focuses on the manual creation of
             recipes, patches, and configuration files, the Yocto Project
             Board Support Package (BSP) tools are available to automate
             this process with existing content and work well to create the
             initial framework and boilerplate code.
             For details on these tools, see the
             "<ulink url='&YOCTO_DOCS_BSP_URL;#using-the-yocto-projects-bsp-tools'>Using the Yocto Project's BSP Tools</ulink>"
             section in the Yocto Project Board Support Package (BSP) Developer's
             Guide.
         </para>
     </section>
 </chapter>
 <!--
 vim: expandtab tw=80 ts=4
 -->
	<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
	"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
	[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >

	<chapter id='kernel-dev-intro'>
	<title>Introduction</title>

	<!--
	<para>
	<emphasis>AR - Darren Hart:</emphasis> See if the concepts in these
	three bullets are adequately covered in somewhere in this manual:
	<itemizedlist>
	<listitem><para>Do we convey that our kernel Git repositories
	have a clear and continuous history, similar to the way the
	kernel Git repositories for <filename>kernel.org</filename>
	do.
	</para></listitem>
	<listitem><para>Does the manual note that Yocto Project delivers
	a key set of supported kernel types, where
	each type is tailored to meet a specific use (e.g. networking,
	consumer, devices, and so forth).</para></listitem>
	<listitem><para>Do we convey that the Yocto Project uses a
	Git branching strategy that, from a
	developer's point of view, results in a linear path from the
	baseline kernel.org, through a select group of features and
	ends with their BSP-specific commits.</para></listitem>
	</itemizedlist>
	</para>
	-->

	<section id='kernel-dev-overview'>
	<title>Overview</title>

	<para>
	Regardless of how you intend to make use of the Yocto Project,
	chances are you will work with the Linux kernel.
	This manual provides background information on the Yocto Linux kernel
	<ulink url='&YOCTO_DOCS_DEV_URL;#metadata'>Metadata</ulink>,
	describes common tasks you can perform using the kernel tools,
	and shows you how to use the kernel Metadata needed to work with
	the kernel inside the Yocto Project.
	</para>

	<para>
	Each Yocto Project release has a set of linux-yocto recipes, whose
	Git repositories you can view in the Yocto
	<ulink url='&YOCTO_GIT_URL;'>Source Repositories</ulink> under
	the "Yocto Linux Kernel" heading.
	New recipes for the release track the latest upstream developments
	and introduce newly-supported platforms.
	Previous recipes in the release are refreshed and supported for at
	least one additional release.
	As they align, these previous releases are updated to include the
	latest from the
	<ulink url='&YOCTO_HOME_URL;/organization/long-term-support-initiative-ltsi'>Long Term Support Initiative</ulink>
	(LTSI) project.
	Also included is a linux-yocto development recipe
	(<filename>linux-yocto-dev.bb</filename>) should you want to work
	with the very latest in upstream Linux kernel development and
	kernel Metadata development.
	</para>

	<para>
	The Yocto Project also provides a powerful set of kernel
	tools for managing Linux kernel sources and configuration data.
	You can use these tools to make a single configuration change,
	apply multiple patches, or work with your own kernel sources.
	</para>

	<para>
	In particular, the kernel tools allow you to generate configuration
	fragments that specify only what you must, and nothing more.
	Configuration fragments only need to contain the highest level
	visible <filename>CONFIG</filename> options as presented by the Linux
	kernel <filename>menuconfig</filename> system.
	Contrast this against a complete Linux kernel
	<filename>.config</filename>, which includes all the automatically
	selected <filename>CONFIG</filename> options.
	This efficiency reduces your maintenance effort and allows you
	to further separate your configuration in ways that make sense for
	your project.
	A common split separates policy and hardware.
	For example, all your kernels might support
	the <filename>proc</filename> and <filename>sys</filename> filesystems,
	but only specific boards require sound, USB, or specific drivers.
	Specifying these configurations individually allows you to aggregate
	them together as needed, but maintains them in only one place.
	Similar logic applies to separating source changes.
	</para>

	<para>
	If you do not maintain your own kernel sources and need to make
	only minimal changes to the sources, the released recipes provide a
	vetted base upon which to layer your changes.
	Doing so allows you to benefit from the continual kernel
	integration and testing performed during development of the
	Yocto Project.
	</para>

	<para>
	If, instead, you have a very specific Linux kernel source tree
	and are unable to align with one of the official linux-yocto
	recipes, an alternative exists by which you can use the Yocto
	Project Linux kernel tools with your own kernel sources.
	</para>
	</section>

	<section id='kernel-dev-other-resources'>
	<title>Other Resources</title>

	<para>
	The sections that follow provide instructions for completing
	specific Linux kernel development tasks.
	These instructions assume you are comfortable working with
	<ulink url='http://openembedded.org/wiki/Bitbake'>BitBake</ulink>
	recipes and basic open-source development tools.
	Understanding these concepts will facilitate the process of working
	with the kernel recipes.
	If you find you need some additional background, please be sure to
	review and understand the following documentation:
	<itemizedlist>
	<listitem><para><ulink url='&YOCTO_DOCS_QS_URL;'>Yocto Project Quick Start</ulink>
	</para></listitem>
	<listitem><para>The "<ulink url='&YOCTO_DOCS_DEV_URL;#dev-modifying-source-code'>Modifying Source Code</ulink>"
	section in the Yocto Project Development Manual
	</para></listitem>
	<listitem><para>The "<ulink url='&YOCTO_DOCS_DEV_URL;#understanding-and-creating-layers'>Understanding and Creating Layers</ulink>" section
	in the Yocto Project Development Manual</para></listitem>
	<listitem><para>The "<ulink url='&YOCTO_DOCS_DEV_URL;#modifying-the-kernel'>Modifying the Kernel</ulink>" section
	in the Yocto Project Development Manual.</para></listitem>
	</itemizedlist>
	</para>

	<para>
	Finally, while this document focuses on the manual creation of
	recipes, patches, and configuration files, the Yocto Project
	Board Support Package (BSP) tools are available to automate
	this process with existing content and work well to create the
	initial framework and boilerplate code.
	For details on these tools, see the
	"<ulink url='&YOCTO_DOCS_BSP_URL;#using-the-yocto-projects-bsp-tools'>Using the Yocto Project's BSP Tools</ulink>"
	section in the Yocto Project Board Support Package (BSP) Developer's
	Guide.
	</para>
	</section>
	</chapter>
	<!--
	vim: expandtab tw=80 ts=4
	-->