documentation/kernel-dev/maint-appx.rst

10 This section describes construction of the Yocto Project kernel source
12 Linux kernel repositories. These kernel repositories are found under the
18 divisions found in a Yocto Linux kernel. Thus, the Yocto Project Linux
19 kernel repository (or tree) and accompanying Metadata in the
20 ``yocto-kernel-cache`` are built.
23 particular Yocto Project Linux kernel repository and use it to build
27 in the Yocto Project Linux kernel in any clone of the Yocto Project
28 Linux kernel source repository and ``yocto-kernel-cache`` Git trees. For
30 kernel that branches off ``linux.org`` version 4.12 and the
31 ``yocto-kernel-cache``, which contains stores of kernel Metadata::
34    $ git clone git://git.yoctoproject.org/linux-kernel-cache
37 how to set up a local Git repository of the Yocto Project Linux kernel
39 ":ref:`kernel-dev/common:preparing the build host to work on the kernel`"
42 Once you have cloned the kernel Git repository and the cache of Metadata
49 kernel. For example, the following commands check out the
50 "standard/beagleboard" branch of the Yocto Linux kernel repository and
51 the "yocto-4.12" branch of the ``yocto-kernel-cache`` repository::
54    $ git checkout -b my-kernel-4.12 remotes/origin/standard/beagleboard
55    $ cd ~/linux-kernel-cache
60    Branches in the ``yocto-kernel-cache`` repository correspond to Yocto Linux
61    kernel versions (e.g. "yocto-4.12", "yocto-4.10", "yocto-4.9", and so forth).
64 see a snapshot of all the kernel source files used to build that
65 particular Yocto Linux kernel for a particular board.
68 kernel, you need to examine the ``yocto-kernel-cache`` Git repository.
69 As mentioned, branches in the ``yocto-kernel-cache`` repository
70 correspond to Yocto Linux kernel versions (e.g. ``yocto-4.12``).
75 ``yocto-kernel-cache`` repository for feature descriptions and patches
76 is not an effective way to determine what is in a particular kernel
79 to the kernel.
83    Ground up reconstruction of the complete kernel tree is an action
85    cycle. When you create a clone of the kernel Git repository, you are
89 constructs the Yocto Project kernel source Git repository (or tree)
91 top-level kernel feature or BSP. The following actions effectively
95 1. *Pass Feature to the OpenEmbedded Build System:* A top-level kernel
96    feature is passed to the kernel build subsystem. Normally, this
97    feature is a BSP for a particular kernel type.
102    -  The in-tree kernel-cache directories, which are located in the
103       :yocto_git:`yocto-kernel-cache </yocto-kernel-cache/tree/bsp>`
107    -  Areas pointed to by :term:`SRC_URI` statements found in kernel recipes.
117    equivalent script that is already part of the shipped kernel.
130    ``yocto-kernel-cache`` repository. These files are descriptions of
136    actions listed in the ``yocto-kernel-cache`` directories are applied
143 The kernel tree and cache are ready for developer consumption to be
144 locally cloned, configured, and built into a Yocto Project kernel
149    -  The generated ``yocto-kernel-cache`` repository adds to the kernel
153       Project kernel repositories at :yocto_git:`/` is the
158       patches specific to a deployment. Any additions to the kernel
161    -  The full kernel tree that you see on :yocto_git:`/` is
164       kernel for a given release. You can see the script (``kgit-scc``)
166       :yocto_git:`yocto-kernel-tools </yocto-kernel-tools/tree/tools>`
169    -  The steps used to construct the full kernel tree are the same
170       steps that BitBake uses when it builds a kernel image.
175 Once you have cloned a Yocto Linux kernel repository and the cache
176 repository (``yocto-kernel-cache``) onto your development system, you
177 can consider the compilation phase of kernel development, which is
178 building a kernel image. Some prerequisites are validated by
182    kernel Git repository.
184 -  A BSP build branch with Metadata exists in the ``yocto-kernel-cache``
185    repository. The branch is based on the Yocto Linux kernel version and
187    ``yocto-kernel-cache/bsp`` directory. For example, features and
189    ``linux-yocto_4.12`` kernel reside in the following area of the
190    ``yocto-kernel-cache`` repository: yocto-kernel-cache/bsp/beaglebone
195       the ``yocto-kernel-cache`` repository.
201 Before building a kernel, the build process verifies the tree and
202 configures the kernel by processing all of the configuration "fragments"
204 are compiled, associated kernel configuration fragments are noted and
213 board's template, kernel compilation is started and a kernel image is
216 The other thing that you notice once you configure a kernel is that the
217 build process generates a build tree that is separate from your kernel's
221 kernel types (e.g. "standard")::
225 The existing support in the ``kernel.org`` tree achieves this default