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diff --git a/poky/documentation/kernel-dev/kernel-dev-intro.xml b/poky/documentation/kernel-dev/kernel-dev-intro.xml new file mode 100644 index 000000000..4e4fd282a --- /dev/null +++ b/poky/documentation/kernel-dev/kernel-dev-intro.xml @@ -0,0 +1,259 @@ +<!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> + +<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 describes how to set up your build host to support + kernel development, introduces the kernel development process, + provides background information on the Yocto Linux kernel + <ulink url='&YOCTO_DOCS_REF_URL;#metadata'>Metadata</ulink>, + describes common tasks you can perform using the kernel tools, + shows you how to use the kernel Metadata needed to work with + the kernel inside the Yocto Project, and provides insight into how + the Yocto Project team develops and maintains Yocto Linux kernel + Git repositories and Metadata. + </para> + + <para> + Each Yocto Project release has a set of Yocto Linux kernel 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 Linux kernel + upstream developments from + <ulink url='http://www.kernel.org'></ulink> and introduce + newly-supported platforms. + Previous recipes in the release are refreshed and supported for at + least one additional Yocto Project release. + As they align, these previous releases are updated to include the + latest from the Long Term Support Initiative (LTSI) project. + You can learn more about Yocto Linux kernels and LTSI in the + "<link linkend='kernel-big-picture'>Yocto Project Kernel Development and Maintenance</link>" + section. + </para> + + <para> + Also included is a Yocto Linux kernel development recipe + (<filename>linux-yocto-dev.bb</filename>) should you want to work + with the very latest in upstream Yocto Linux kernel development and + kernel Metadata development. + <note> + For more on Yocto Linux kernels, see the + "<link linkend='kernel-big-picture'>Yocto Project Kernel Development and Maintenance</link> + section. + </note> + </para> + + <para> + The Yocto Project also provides a powerful set of kernel + tools for managing Yocto 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 + Yocto Linux kernel <filename>menuconfig</filename> system. + Contrast this against a complete Yocto Linux kernel + <filename>.config</filename> file, 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 Yocto Linux kernel + recipes, an alternative exists by which you can use the Yocto + Project Linux kernel tools with your own kernel sources. + </para> + + <para> + The remainder of this manual provides 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_BRIEF_URL;'>Yocto Project Quick Build</ulink> + document. + </para></listitem> + <listitem><para> + <ulink url='&YOCTO_DOCS_OM_URL;'>Yocto Project Overview and Concepts Manual</ulink>. + </para></listitem> + <listitem><para> + <ulink url='&YOCTO_DOCS_SDK_URL;#using-devtool-in-your-sdk-workflow'><filename>devtool</filename> workflow</ulink> + as described in the Yocto Project Application Development and + the Extensible Software Development Kit (eSDK) 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 Tasks Manual. + </para></listitem> + <listitem><para> + The + "<link linkend='kernel-modification-workflow'>Kernel Modification Workflow</link>" + section. + </para></listitem> + </itemizedlist> + </para> +</section> + +<section id='kernel-modification-workflow'> + <title>Kernel Modification Workflow</title> + + <para> + Kernel modification involves changing the Yocto Project kernel, + which could involve changing configuration options as well as adding + new kernel recipes. + Configuration changes can be added in the form of configuration + fragments, while recipe modification comes through the kernel's + <filename>recipes-kernel</filename> area in a kernel layer you create. + </para> + + <para> + This section presents a high-level overview of the Yocto Project + kernel modification workflow. + The illustration and accompanying list provide general information + and references for further information. + <imagedata fileref="figures/kernel-dev-flow.png" + width="9in" depth="5in" align="center" scalefit="1" /> + </para> + + <para> + <orderedlist> + <listitem><para> + + + <emphasis>Set up Your Host Development System to Support + Development Using the Yocto Project</emphasis>: + See the + "<ulink url='&YOCTO_DOCS_DEV_URL;#dev-manual-start'>Setting Up the Development Host to Use the Yocto Project</ulink>" + section in the Yocto Project Development Tasks Manual for + options on how to get a build host ready to use the Yocto + Project. + </para></listitem> + <listitem><para> + <emphasis>Set Up Your Host Development System for Kernel Development:</emphasis> + It is recommended that you use <filename>devtool</filename> + and an extensible SDK for kernel development. + Alternatively, you can use traditional kernel development + methods with the Yocto Project. + Either way, there are steps you need to take to get the + development environment ready.</para> + + <para>Using <filename>devtool</filename> and the eSDK requires + that you have a clean build of the image and that you are + set up with the appropriate eSDK. + For more information, see the + "<link linkend='getting-ready-to-develop-using-devtool'>Getting Ready to Develop Using <filename>devtool</filename></link>" + section.</para> + + <para>Using traditional kernel development requires that you + have the kernel source available in an isolated local Git + repository. + For more information, see the + "<link linkend='getting-ready-for-traditional-kernel-development'>Getting Ready for Traditional Kernel Development</link>" + section. + </para></listitem> + <listitem><para> + <emphasis>Make Changes to the Kernel Source Code if + applicable:</emphasis> + Modifying the kernel does not always mean directly + changing source files. + However, if you have to do this, you make the changes to the + files in the eSDK's Build Directory if you are using + <filename>devtool</filename>. + For more information, see the + "<link linkend='using-devtool-to-patch-the-kernel'>Using <filename>devtool</filename> to Patch the Kernel</link>" + section.</para> + + <para>If you are using traditional kernel development, you + edit the source files in the kernel's local Git repository. + For more information, see the + "<link linkend='using-traditional-kernel-development-to-patch-the-kernel'>Using Traditional Kernel Development to Patch the Kernel</link>" + section. + </para></listitem> + <listitem><para> + <emphasis>Make Kernel Configuration Changes if + Applicable:</emphasis> + If your situation calls for changing the kernel's + configuration, you can use + <link linkend='using-menuconfig'><filename>menuconfig</filename></link>, + which allows you to interactively develop and test the + configuration changes you are making to the kernel. + Saving changes you make with <filename>menuconfig</filename> + updates the kernel's <filename>.config</filename> file. + <note><title>Warning</title> + Try to resist the temptation to directly edit an + existing <filename>.config</filename> file, which is + found in the Build Directory among the source code + used for the build. + Doing so, can produce unexpected results when the + OpenEmbedded build system regenerates the configuration + file. + </note> + Once you are satisfied with the configuration + changes made using <filename>menuconfig</filename> + and you have saved them, you can directly compare the + resulting <filename>.config</filename> file against an + existing original and gather those changes into a + <link linkend='creating-config-fragments'>configuration fragment file</link> + to be referenced from within the kernel's + <filename>.bbappend</filename> file.</para> + + <para>Additionally, if you are working in a BSP layer + and need to modify the BSP's kernel's configuration, + you can use <filename>menuconfig</filename>. + </para></listitem> + <listitem><para> + <emphasis>Rebuild the Kernel Image With Your Changes:</emphasis> + Rebuilding the kernel image applies your changes. + Depending on your target hardware, you can verify your changes + on actual hardware or perhaps QEMU. + </para></listitem> + </orderedlist> + The remainder of this developer's guide covers common tasks typically + used during kernel development, advanced Metadata usage, and Yocto Linux + kernel maintenance concepts. + </para> +</section> + +</chapter> +<!-- +vim: expandtab tw=80 ts=4 +--> |
