documentation/kernel-dev/intro.rst

1 .. SPDX-License-Identifier: CC-BY-SA-2.0-UK
11 are you will work with the Linux kernel. This manual describes how to
12 set up your build host to support kernel development, introduces the
13 kernel development process, provides background information on the Yocto
14 Linux kernel :term:`Metadata`, describes
15 common tasks you can perform using the kernel tools, shows you how to
16 use the kernel Metadata needed to work with the kernel inside the Yocto
18 and maintains Yocto Linux kernel Git repositories and Metadata.
20 Each Yocto Project release has a set of Yocto Linux kernel recipes,
21 whose Git repositories you can view in the Yocto
22 :yocto_git:`Source Repositories <>` under the "Yocto Linux Kernel"
23 heading. New recipes for the release track the latest Linux kernel
24 upstream developments from https://www.kernel.org and introduce
25 newly-supported platforms. Previous recipes in the release are refreshed
29 about Yocto Linux kernels and LTSI in the
30 ":ref:`kernel-dev/concepts-appx:yocto project kernel development and maintenance`" section.
32 Also included is a Yocto Linux kernel development recipe
33 (``linux-yocto-dev.bb``) should you want to work with the very latest in
34 upstream Yocto Linux kernel development and kernel Metadata development.
39    ":ref:`kernel-dev/concepts-appx:yocto project kernel development and maintenance`"
42 The Yocto Project also provides a powerful set of kernel tools for
43 managing Yocto Linux kernel sources and configuration data. You can use
45 patches, or work with your own kernel sources.
47 In particular, the kernel tools allow you to generate configuration
50 ``CONFIG`` options as presented by the Yocto Linux kernel ``menuconfig``
51 system. Contrast this against a complete Yocto Linux kernel ``.config``
54 further separate your configuration in ways that make sense for your
59 as needed, but maintains them in only one place. Similar logic applies
62 If you do not maintain your own kernel sources and need to make only
65 from the continual kernel integration and testing performed during
68 If, instead, you have a very specific Linux kernel source tree and are
69 unable to align with one of the official Yocto Linux kernel recipes,
70 you have a way to use the Yocto Project Linux kernel tools with your
71 own kernel sources.
74 specific Linux kernel development tasks. These instructions assume you
76 open-source development tools. Understanding these concepts will
77 facilitate the process of working with the kernel recipes. If you find
81 -  :doc:`/brief-yoctoprojectqs/index` document.
83 -  :doc:`/overview-manual/index`.
85 -  :ref:`devtool
86    workflow <sdk-manual/extensible:using \`\`devtool\`\` in your sdk workflow>`
87    as described in the Yocto Project Application Development and the
90 -  The ":ref:`dev-manual/layers:understanding and creating layers`"
91    section in the Yocto Project Development Tasks Manual.
93 -  The ":ref:`kernel-dev/intro:kernel modification workflow`" section.
95 Kernel Modification Workflow
98 Kernel modification involves changing the Yocto Project kernel, which
100 kernel recipes. Configuration changes can be added in the form of
102 kernel's ``recipes-kernel`` area in a kernel layer you create.
104 This section presents a high-level overview of the Yocto Project kernel
108 .. image:: figures/kernel-dev-flow.png
112    Yocto Project*: See the ":doc:`/dev-manual/start`" section in
116 #. *Set Up Your Host Development System for Kernel Development:* It is
117    recommended that you use ``devtool`` for kernel
118    development. Alternatively, you can use traditional kernel
125    ":ref:`kernel-dev/common:getting ready to develop using \`\`devtool\`\``"
128    Using traditional kernel development requires that you have the
129    kernel source available in an isolated local Git repository. For more
131    ":ref:`kernel-dev/common:getting ready for traditional kernel development`"
134 #. *Make Changes to the Kernel Source Code if applicable:* Modifying the
135    kernel does not always mean directly changing source files. However,
136    if you have to do this, you make the changes to the files in the
139    ":ref:`kernel-dev/common:using \`\`devtool\`\` to patch the kernel`"
142    If you are using traditional kernel development, you edit the source
143    files in the kernel's local Git repository. For more information, see the
144    ":ref:`kernel-dev/common:using traditional kernel development to patch the kernel`"
147 #. *Make Kernel Configuration Changes if Applicable:* If your situation
148    calls for changing the kernel's configuration, you can use
149    :ref:`menuconfig <kernel-dev/common:using \`\`menuconfig\`\`>`,
152    making to the kernel. Saving changes you make with ``menuconfig``
153    updates the kernel's ``.config`` file.
158       file, which is found in the :term:`Build Directory` among the source code
166    :ref:`configuration fragment file <kernel-dev/common:creating configuration fragments>` to be
167    referenced from within the kernel's ``.bbappend`` file.
169    Additionally, if you are working in a BSP layer and need to modify
170    the BSP's kernel's configuration, you can use ``menuconfig``.
172 #. *Rebuild the Kernel Image With Your Changes:* Rebuilding the kernel
177 used during kernel development, advanced Metadata usage, and Yocto Linux
178 kernel maintenance concepts.