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kernel-dev: Minor edits to the "Advanced Kernel Concepts" appendix
(From yocto-docs rev: 645b642965ffcbb12f171e11a53b4efe5d0fd756) Signed-off-by: Scott Rifenbark <srifenbark@gmail.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
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Scott Rifenbark
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Richard Purdie
Richard Purdie
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@@ -9,7 +9,7 @@
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<title>Yocto Project Kernel Development and Maintenance</title>
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<para>
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Kernels available through the Yocto Project (Linux Yocto kernels),
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Kernels available through the Yocto Project (Yocto Linux kernels),
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like other kernels, are based off the Linux kernel releases from
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<ulink url='http://www.kernel.org'></ulink>.
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At the beginning of a major Linux kernel development cycle, the
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@@ -29,18 +29,18 @@
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<para>
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This balance allows the Yocto Project team to deliver the most
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up-to-date Linux Yocto kernel possible, while still ensuring that
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up-to-date Yocto Linux kernel possible, while still ensuring that
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the team has a stable official release for the baseline Linux
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kernel version.
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</para>
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<para>
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As implied earlier, the ultimate source for Linux Yocto kernels
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As implied earlier, the ultimate source for Yocto Linux kernels
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are released kernels from <filename>kernel.org</filename>.
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In addition to a foundational kernel from
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<filename>kernel.org</filename>, the available Yocto Linux kernels
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contain a mix of important new mainline developments, non-mainline
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developments (when there is no alternative), Board Support Package
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developments (when no alternative exists), Board Support Package
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(BSP) developments, and custom features.
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These additions result in a commercially released Yocto
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Project Linux kernel that caters to specific embedded designer
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@@ -69,6 +69,16 @@
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Project Release 2.1.
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This kernel is based on the Linux 4.4 released kernel.
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</para></listitem>
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<listitem><para>
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<emphasis><filename>linux-yocto-4.6</filename>:</emphasis>
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A temporary kernel that is not tied to any Yocto Project
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release.
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</para></listitem>
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<listitem><para>
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<emphasis><filename>linux-yocto-4.8</filename>:</emphasis>
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The stable yocto Project kernel to use with the Yocto
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Project Release 2.2.
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</para></listitem>
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<listitem><para>
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<emphasis><filename>linux-yocto-4.9</filename>:</emphasis>
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The stable Yocto Project kernel to use with the Yocto
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@@ -94,6 +104,10 @@
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tree.
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This repository is useful when working on the linux-yocto
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kernel.
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For more information on this "Advanced Kernel Metadata",
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see the
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"<link linkend='kernel-dev-advanced'>Working With Advanced Metadata (<filename>yocto-kernel-cache</filename>)</link>"
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Chapter.
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</para></listitem>
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<listitem><para>
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<emphasis><filename>linux-yocto-dev</filename>:</emphasis>
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@@ -157,9 +171,9 @@
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introduces new bugs.
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These consequences are the basic properties of upstream
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Linux kernel development and are managed by the Yocto Project
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team's Linux Yocto kernel development strategy.
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team's Yocto Linux kernel development strategy.
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It is the Yocto Project team's policy to not back-port minor
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features to the released Linux Yocto kernel.
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features to the released Yocto Linux kernel.
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They only consider back-porting significant technological
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jumps ‐ and, that is done after a complete gap analysis.
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The reason for this policy is that back-porting any small to
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@@ -169,19 +183,19 @@
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<para>
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The policies described in this section result in both a stable
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and a cutting edge Linux Yocto kernel that mixes forward ports of
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and a cutting edge Yocto Linux kernel that mixes forward ports of
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existing Linux kernel features and significant and critical new
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functionality.
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Forward porting Linux kernel functionality into the Linux Yocto
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Forward porting Linux kernel functionality into the Yocto Linux
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kernels available through the Yocto Project can be thought of as
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a "micro uprev."
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The many “micro uprevs” produce a Linux Yocto kernel version with
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The many “micro uprevs” produce a Yocto Linux kernel version with
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a mix of important new mainline, non-mainline, BSP developments
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and feature integrations.
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This Yocto Linux kernel gives insight into new features and
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allows focused amounts of testing to be done on the kernel,
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which prevents surprises when selecting the next major uprev.
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The quality of these cutting edge Linux Yocto kernels is evolving
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The quality of these cutting edge Yocto Linux kernels is evolving
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and the kernels are used in leading edge feature and BSP
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development.
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</para>
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@@ -211,13 +225,12 @@
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<itemizedlist>
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<listitem><para>
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Git is the obvious SCM for meeting the Yocto Linux
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kernel organizational and structural goals
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described in this section.
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Not only is Git the SCM for Linux kernel
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development in <filename>kernel.org</filename> but,
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Git continues to grow in popularity and supports
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many different work flows, front-ends and
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management techniques.
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kernel organizational and structural goals described
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in this section.
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Not only is Git the SCM for Linux kernel development in
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<filename>kernel.org</filename> but, Git continues to
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grow in popularity and supports many different work
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flows, front-ends and management techniques.
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</para></listitem>
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<listitem><para>
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You can find documentation on Git at
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@@ -251,12 +264,11 @@
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</para>
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<para>
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This "tree-like" architecture results in a tree that has
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features organized to be specific for particular
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functionality, single kernel types, or a subset of kernel
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types.
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Thus, the user has the ability to see the added
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features and the commits that make up those features.
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This "tree-like" architecture results in a structure that has
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features organized to be specific for particular functionality,
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single kernel types, or a subset of kernel types.
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Thus, the user has the ability to see the added features and the
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commits that make up those features.
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In addition to being able to see added features, the user
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can also view the history of what made up the baseline
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Linux kernel.
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@@ -388,7 +400,8 @@
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<para>
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Because commits only change at significant release points in the
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product life cycle, developers can work on a branch created
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from the last relevant commit in the shipped Yocto Project kernel.
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from the last relevant commit in the shipped Yocto Project Linux
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kernel.
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As mentioned previously, the structure is transparent to the
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developer because the kernel tree is left in this state after
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cloning and building the kernel.
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@@ -476,7 +489,9 @@
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section.
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You can also reference the
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"<link linkend='using-devtool-to-patch-the-kernel'>Using <filename>devtool</filename> to Patch the Kernel</link>"
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section for a detailed example that modifies the kernel.
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and
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"<link linkend='using-traditional-kernel-development-to-patch-the-kernel'>Using Traditional Kernel Development to Patch the Kernel</link>"
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sections for detailed example that modifies the kernel.
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</para>
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</section>
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@@ -513,30 +528,32 @@
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<para>
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To determine whether or not a given option is "hardware" or
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"non-hardware", the kernel Metadata contains files that
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"non-hardware", the kernel Metadata in
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<filename>yocto-kernel-cache</filename> contains files that
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classify individual or groups of options as either hardware
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or non-hardware.
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To better show this, consider a situation where the
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Yocto Project kernel cache contains the following files:
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<filename>yocto-kernel-cache</filename> contains the following
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files:
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<literallayout class='monospaced'>
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kernel-cache/features/drm-psb/hardware.cfg
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kernel-cache/features/kgdb/hardware.cfg
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kernel-cache/ktypes/base/hardware.cfg
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kernel-cache/bsp/mti-malta32/hardware.cfg
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kernel-cache/bsp/fsl-mpc8315e-rdb/hardware.cfg
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kernel-cache/bsp/qemu-ppc32/hardware.cfg
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kernel-cache/bsp/qemuarma9/hardware.cfg
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kernel-cache/bsp/mti-malta64/hardware.cfg
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kernel-cache/bsp/arm-versatile-926ejs/hardware.cfg
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kernel-cache/bsp/common-pc/hardware.cfg
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kernel-cache/bsp/common-pc-64/hardware.cfg
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kernel-cache/features/rfkill/non-hardware.cfg
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kernel-cache/ktypes/base/non-hardware.cfg
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kernel-cache/features/aufs/non-hardware.kcf
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kernel-cache/features/ocf/non-hardware.kcf
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kernel-cache/ktypes/base/non-hardware.kcf
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kernel-cache/ktypes/base/hardware.kcf
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kernel-cache/bsp/qemu-ppc32/hardware.kcf
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yocto-kernel-cache/features/drm-psb/hardware.cfg
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yocto-kernel-cache/features/kgdb/hardware.cfg
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yocto-kernel-cache/ktypes/base/hardware.cfg
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yocto-kernel-cache/bsp/mti-malta32/hardware.cfg
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yocto-kernel-cache/bsp/fsl-mpc8315e-rdb/hardware.cfg
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yocto-kernel-cache/bsp/qemu-ppc32/hardware.cfg
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yocto-kernel-cache/bsp/qemuarma9/hardware.cfg
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yocto-kernel-cache/bsp/mti-malta64/hardware.cfg
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yocto-kernel-cache/bsp/arm-versatile-926ejs/hardware.cfg
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yocto-kernel-cache/bsp/common-pc/hardware.cfg
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yocto-kernel-cache/bsp/common-pc-64/hardware.cfg
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yocto-kernel-cache/features/rfkill/non-hardware.cfg
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yocto-kernel-cache/ktypes/base/non-hardware.cfg
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yocto-kernel-cache/features/aufs/non-hardware.kcf
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yocto-kernel-cache/features/ocf/non-hardware.kcf
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yocto-kernel-cache/ktypes/base/non-hardware.kcf
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yocto-kernel-cache/ktypes/base/hardware.kcf
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yocto-kernel-cache/bsp/qemu-ppc32/hardware.kcf
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</literallayout>
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The following list provides explanations for the various
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files:
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