sphinx: initial sphinx support

This commit is autogenerated pandoc to generate an inital set
of reST files based on DocBook XML files.

A .rst file is generated for each .xml files in all manuals with this
command:

cd <manual>
for i in *.xml; do \
  pandoc -f docbook -t rst --shift-heading-level-by=-1 \
  $i -o $(basename $i .xml).rst \
done

The conversion was done with: pandoc 2.9.2.1-91 (Arch Linux).

Also created an initial top level index file for each document, and
added all 'books' to the top leve index.rst file.

The YP manuals layout is organized as:

Book
  Chapter
    Section
      Section
        Section

Sphinx uses section headers to create the document structure.
ReStructuredText defines sections headers like that:

   To break longer text up into sections, you use section headers. These
   are a single line of text (one or more words) with adornment: an
   underline alone, or an underline and an overline together, in dashes
   "-----", equals "======", tildes "~~~~~~" or any of the
   non-alphanumeric characters = - ` : ' " ~ ^ _ * + # < > that you feel
   comfortable with. An underline-only adornment is distinct from an
   overline-and-underline adornment using the same character. The
   underline/overline must be at least as long as the title text. Be
   consistent, since all sections marked with the same adornment style
   are deemed to be at the same level:

Let's define the following convention when converting from Docbook:

Book                => overline ===   (Title)
  Chapter           => overline ***   (1.)
    Section         => ====           (1.1)
      Section       => ----           (1.1.1)
        Section     => ~~~~           (1.1.1.1)
          Section   => ^^^^           (1.1.1.1.1)

During the conversion with pandoc, we used --shift-heading-level=-1 to
convert most of DocBook headings automatically. However with this
setting, the Chapter header was removed, so I added it back
manually. Without this setting all headings were off by one, which was
more difficult to manually fix.

At least with this change, we now have the same TOC with Sphinx and
DocBook.

(From yocto-docs rev: 3c73d64a476d4423ee4c6808c685fa94d88d7df8)

Signed-off-by: Nicolas Dechesne <nicolas.dechesne@linaro.org>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 762 insertions, 0 deletions

diff --git a/documentation/kernel-dev/kernel-dev-advanced.rst b/documentation/kernel-dev/kernel-dev-advanced.rst
new file mode 100644
index 0000000000..be76bd7b52
--- /dev/null
+++ b/documentation/kernel-dev/kernel-dev-advanced.rst
@@ -0,0 +1,762 @@
+*******************************************************
+Working with Advanced Metadata (``yocto-kernel-cache``)
+*******************************************************
+
+.. _kernel-dev-advanced-overview:
+
+Overview
+========
+
+In addition to supporting configuration fragments and patches, the Yocto
+Project kernel tools also support rich
+`Metadata <&YOCTO_DOCS_REF_URL;#metadata>`__ that you can use to define
+complex policies and Board Support Package (BSP) support. The purpose of
+the Metadata and the tools that manage it is to help you manage the
+complexity of the configuration and sources used to support multiple
+BSPs and Linux kernel types.
+
+Kernel Metadata exists in many places. One area in the Yocto Project
+`Source Repositories <&YOCTO_DOCS_OM_URL;#source-repositories>`__ is the
+``yocto-kernel-cache`` Git repository. You can find this repository
+grouped under the "Yocto Linux Kernel" heading in the `Yocto Project
+Source Repositories <&YOCTO_GIT_URL;>`__.
+
+Kernel development tools ("kern-tools") exist also in the Yocto Project
+Source Repositories under the "Yocto Linux Kernel" heading in the
+``yocto-kernel-tools`` Git repository. The recipe that builds these
+tools is ``meta/recipes-kernel/kern-tools/kern-tools-native_git.bb`` in
+the `Source Directory <&YOCTO_DOCS_REF_URL;#source-directory>`__ (e.g.
+``poky``).
+
+Using Kernel Metadata in a Recipe
+=================================
+
+As mentioned in the introduction, the Yocto Project contains kernel
+Metadata, which is located in the ``yocto-kernel-cache`` Git repository.
+This Metadata defines Board Support Packages (BSPs) that correspond to
+definitions in linux-yocto recipes for corresponding BSPs. A BSP
+consists of an aggregation of kernel policy and enabled
+hardware-specific features. The BSP can be influenced from within the
+linux-yocto recipe.
+
+.. note::
+
+   A Linux kernel recipe that contains kernel Metadata (e.g. inherits
+   from the
+   linux-yocto.inc
+   file) is said to be a "linux-yocto style" recipe.
+
+Every linux-yocto style recipe must define the
+```KMACHINE`` <&YOCTO_DOCS_REF_URL;#var-KMACHINE>`__ variable. This
+variable is typically set to the same value as the ``MACHINE`` variable,
+which is used by `BitBake <&YOCTO_DOCS_REF_URL;#bitbake-term>`__.
+However, in some cases, the variable might instead refer to the
+underlying platform of the ``MACHINE``.
+
+Multiple BSPs can reuse the same ``KMACHINE`` name if they are built
+using the same BSP description. Multiple Corei7-based BSPs could share
+the same "intel-corei7-64" value for ``KMACHINE``. It is important to
+realize that ``KMACHINE`` is just for kernel mapping, while ``MACHINE``
+is the machine type within a BSP Layer. Even with this distinction,
+however, these two variables can hold the same value. See the `BSP
+Descriptions <#bsp-descriptions>`__ section for more information.
+
+Every linux-yocto style recipe must also indicate the Linux kernel
+source repository branch used to build the Linux kernel. The
+```KBRANCH`` <&YOCTO_DOCS_REF_URL;#var-KBRANCH>`__ variable must be set
+to indicate the branch.
+
+.. note::
+
+   You can use the
+   KBRANCH
+   value to define an alternate branch typically with a machine override
+   as shown here from the
+   meta-yocto-bsp
+   layer:
+   ::
+
+           KBRANCH_edgerouter = "standard/edgerouter"
+                  
+
+The linux-yocto style recipes can optionally define the following
+variables: KERNEL_FEATURES LINUX_KERNEL_TYPE
+
+```LINUX_KERNEL_TYPE`` <&YOCTO_DOCS_REF_URL;#var-LINUX_KERNEL_TYPE>`__
+defines the kernel type to be used in assembling the configuration. If
+you do not specify a ``LINUX_KERNEL_TYPE``, it defaults to "standard".
+Together with ``KMACHINE``, ``LINUX_KERNEL_TYPE`` defines the search
+arguments used by the kernel tools to find the appropriate description
+within the kernel Metadata with which to build out the sources and
+configuration. The linux-yocto recipes define "standard", "tiny", and
+"preempt-rt" kernel types. See the "`Kernel Types <#kernel-types>`__"
+section for more information on kernel types.
+
+During the build, the kern-tools search for the BSP description file
+that most closely matches the ``KMACHINE`` and ``LINUX_KERNEL_TYPE``
+variables passed in from the recipe. The tools use the first BSP
+description it finds that match both variables. If the tools cannot find
+a match, they issue a warning.
+
+The tools first search for the ``KMACHINE`` and then for the
+``LINUX_KERNEL_TYPE``. If the tools cannot find a partial match, they
+will use the sources from the ``KBRANCH`` and any configuration
+specified in the ```SRC_URI`` <&YOCTO_DOCS_REF_URL;#var-SRC_URI>`__.
+
+You can use the
+```KERNEL_FEATURES`` <&YOCTO_DOCS_REF_URL;#var-KERNEL_FEATURES>`__
+variable to include features (configuration fragments, patches, or both)
+that are not already included by the ``KMACHINE`` and
+``LINUX_KERNEL_TYPE`` variable combination. For example, to include a
+feature specified as "features/netfilter/netfilter.scc", specify:
+KERNEL_FEATURES += "features/netfilter/netfilter.scc" To include a
+feature called "cfg/sound.scc" just for the ``qemux86`` machine,
+specify: KERNEL_FEATURES_append_qemux86 = " cfg/sound.scc" The value of
+the entries in ``KERNEL_FEATURES`` are dependent on their location
+within the kernel Metadata itself. The examples here are taken from the
+``yocto-kernel-cache`` repository. Each branch of this repository
+contains "features" and "cfg" subdirectories at the top-level. For more
+information, see the "`Kernel Metadata
+Syntax <#kernel-metadata-syntax>`__" section.
+
+Kernel Metadata Syntax
+======================
+
+The kernel Metadata consists of three primary types of files: ``scc``
+ [1]_ description files, configuration fragments, and patches. The
+``scc`` files define variables and include or otherwise reference any of
+the three file types. The description files are used to aggregate all
+types of kernel Metadata into what ultimately describes the sources and
+the configuration required to build a Linux kernel tailored to a
+specific machine.
+
+The ``scc`` description files are used to define two fundamental types
+of kernel Metadata:
+
+-  Features
+
+-  Board Support Packages (BSPs)
+
+Features aggregate sources in the form of patches and configuration
+fragments into a modular reusable unit. You can use features to
+implement conceptually separate kernel Metadata descriptions such as
+pure configuration fragments, simple patches, complex features, and
+kernel types. `Kernel types <#kernel-types>`__ define general kernel
+features and policy to be reused in the BSPs.
+
+BSPs define hardware-specific features and aggregate them with kernel
+types to form the final description of what will be assembled and built.
+
+While the kernel Metadata syntax does not enforce any logical separation
+of configuration fragments, patches, features or kernel types, best
+practices dictate a logical separation of these types of Metadata. The
+following Metadata file hierarchy is recommended: base/ bsp/ cfg/
+features/ ktypes/ patches/
+
+The ``bsp`` directory contains the `BSP
+descriptions <#bsp-descriptions>`__. The remaining directories all
+contain "features". Separating ``bsp`` from the rest of the structure
+aids conceptualizing intended usage.
+
+Use these guidelines to help place your ``scc`` description files within
+the structure:
+
+-  If your file contains only configuration fragments, place the file in
+   the ``cfg`` directory.
+
+-  If your file contains only source-code fixes, place the file in the
+   ``patches`` directory.
+
+-  If your file encapsulates a major feature, often combining sources
+   and configurations, place the file in ``features`` directory.
+
+-  If your file aggregates non-hardware configuration and patches in
+   order to define a base kernel policy or major kernel type to be
+   reused across multiple BSPs, place the file in ``ktypes`` directory.
+
+These distinctions can easily become blurred - especially as out-of-tree
+features slowly merge upstream over time. Also, remember that how the
+description files are placed is a purely logical organization and has no
+impact on the functionality of the kernel Metadata. There is no impact
+because all of ``cfg``, ``features``, ``patches``, and ``ktypes``,
+contain "features" as far as the kernel tools are concerned.
+
+Paths used in kernel Metadata files are relative to base, which is
+either
+```FILESEXTRAPATHS`` <&YOCTO_DOCS_REF_URL;#var-FILESEXTRAPATHS>`__ if
+you are creating Metadata in `recipe-space <#recipe-space-metadata>`__,
+or the top level of
+```yocto-kernel-cache`` <&YOCTO_GIT_URL;/cgit/cgit.cgi/yocto-kernel-cache/tree/>`__
+if you are creating `Metadata outside of the
+recipe-space <#metadata-outside-the-recipe-space>`__.
+
+Configuration
+-------------
+
+The simplest unit of kernel Metadata is the configuration-only feature.
+This feature consists of one or more Linux kernel configuration
+parameters in a configuration fragment file (``.cfg``) and a ``.scc``
+file that describes the fragment.
+
+As an example, consider the Symmetric Multi-Processing (SMP) fragment
+used with the ``linux-yocto-4.12`` kernel as defined outside of the
+recipe space (i.e. ``yocto-kernel-cache``). This Metadata consists of
+two files: ``smp.scc`` and ``smp.cfg``. You can find these files in the
+``cfg`` directory of the ``yocto-4.12`` branch in the
+``yocto-kernel-cache`` Git repository: cfg/smp.scc: define
+KFEATURE_DESCRIPTION "Enable SMP for 32 bit builds" define
+KFEATURE_COMPATIBILITY all kconf hardware smp.cfg cfg/smp.cfg:
+CONFIG_SMP=y CONFIG_SCHED_SMT=y # Increase default NR_CPUS from 8 to 64
+so that platform with # more than 8 processors can be all activated at
+boot time CONFIG_NR_CPUS=64 # The following is needed when setting
+NR_CPUS to something # greater than 8 on x86 architectures, it should be
+automatically # disregarded by Kconfig when using a different arch
+CONFIG_X86_BIGSMP=y You can find general information on configuration
+fragment files in the "`Creating Configuration
+Fragments <#creating-config-fragments>`__" section.
+
+Within the ``smp.scc`` file, the
+```KFEATURE_DESCRIPTION`` <&YOCTO_DOCS_REF_URL;#var-KFEATURE_DESCRIPTION>`__
+statement provides a short description of the fragment. Higher level
+kernel tools use this description.
+
+Also within the ``smp.scc`` file, the ``kconf`` command includes the
+actual configuration fragment in an ``.scc`` file, and the "hardware"
+keyword identifies the fragment as being hardware enabling, as opposed
+to general policy, which would use the "non-hardware" keyword. The
+distinction is made for the benefit of the configuration validation
+tools, which warn you if a hardware fragment overrides a policy set by a
+non-hardware fragment.
+
+.. note::
+
+   The description file can include multiple
+   kconf
+   statements, one per fragment.
+
+As described in the "`Validating
+Configuration <#validating-configuration>`__" section, you can use the
+following BitBake command to audit your configuration: $ bitbake
+linux-yocto -c kernel_configcheck -f
+
+Patches
+-------
+
+Patch descriptions are very similar to configuration fragment
+descriptions, which are described in the previous section. However,
+instead of a ``.cfg`` file, these descriptions work with source patches
+(i.e. ``.patch`` files).
+
+A typical patch includes a description file and the patch itself. As an
+example, consider the build patches used with the ``linux-yocto-4.12``
+kernel as defined outside of the recipe space (i.e.
+``yocto-kernel-cache``). This Metadata consists of several files:
+``build.scc`` and a set of ``*.patch`` files. You can find these files
+in the ``patches/build`` directory of the ``yocto-4.12`` branch in the
+``yocto-kernel-cache`` Git repository.
+
+The following listings show the ``build.scc`` file and part of the
+``modpost-mask-trivial-warnings.patch`` file: patches/build/build.scc:
+patch arm-serialize-build-targets.patch patch
+powerpc-serialize-image-targets.patch patch
+kbuild-exclude-meta-directory-from-distclean-processi.patch # applied by
+kgit # patch kbuild-add-meta-files-to-the-ignore-li.patch patch
+modpost-mask-trivial-warnings.patch patch
+menuconfig-check-lxdiaglog.sh-Allow-specification-of.patch
+patches/build/modpost-mask-trivial-warnings.patch: From
+bd48931bc142bdd104668f3a062a1f22600aae61 Mon Sep 17 00:00:00 2001 From:
+Paul Gortmaker <paul.gortmaker@windriver.com> Date: Sun, 25 Jan 2009
+17:58:09 -0500 Subject: [PATCH] modpost: mask trivial warnings Newer
+HOSTCC will complain about various stdio fcns because . . . char
+\*dump_write = NULL, \*files_source = NULL; int opt; -- 2.10.1 generated
+by cgit v0.10.2 at 2017-09-28 15:23:23 (GMT) The description file can
+include multiple patch statements where each statement handles a single
+patch. In the example ``build.scc`` file, five patch statements exist
+for the five patches in the directory.
+
+You can create a typical ``.patch`` file using ``diff -Nurp`` or
+``git format-patch`` commands. For information on how to create patches,
+see the "`Using ``devtool`` to Patch the
+Kernel <#using-devtool-to-patch-the-kernel>`__" and "`Using Traditional
+Kernel Development to Patch the
+Kernel <#using-traditional-kernel-development-to-patch-the-kernel>`__"
+sections.
+
+Features
+--------
+
+Features are complex kernel Metadata types that consist of configuration
+fragments, patches, and possibly other feature description files. As an
+example, consider the following generic listing: features/myfeature.scc
+define KFEATURE_DESCRIPTION "Enable myfeature" patch
+0001-myfeature-core.patch patch 0002-myfeature-interface.patch include
+cfg/myfeature_dependency.scc kconf non-hardware myfeature.cfg This
+example shows how the ``patch`` and ``kconf`` commands are used as well
+as how an additional feature description file is included with the
+``include`` command.
+
+Typically, features are less granular than configuration fragments and
+are more likely than configuration fragments and patches to be the types
+of things you want to specify in the ``KERNEL_FEATURES`` variable of the
+Linux kernel recipe. See the "`Using Kernel Metadata in a
+Recipe <#using-kernel-metadata-in-a-recipe>`__" section earlier in the
+manual.
+
+Kernel Types
+------------
+
+A kernel type defines a high-level kernel policy by aggregating
+non-hardware configuration fragments with patches you want to use when
+building a Linux kernel of a specific type (e.g. a real-time kernel).
+Syntactically, kernel types are no different than features as described
+in the "`Features <#features>`__" section. The
+```LINUX_KERNEL_TYPE`` <&YOCTO_DOCS_REF_URL;#var-LINUX_KERNEL_TYPE>`__
+variable in the kernel recipe selects the kernel type. For example, in
+the ``linux-yocto_4.12.bb`` kernel recipe found in
+``poky/meta/recipes-kernel/linux``, a
+```require`` <&YOCTO_DOCS_BB_URL;#require-inclusion>`__ directive
+includes the ``poky/meta/recipes-kernel/linux/linux-yocto.inc`` file,
+which has the following statement that defines the default kernel type:
+LINUX_KERNEL_TYPE ??= "standard"
+
+Another example would be the real-time kernel (i.e.
+``linux-yocto-rt_4.12.bb``). This kernel recipe directly sets the kernel
+type as follows: LINUX_KERNEL_TYPE = "preempt-rt"
+
+.. note::
+
+   You can find kernel recipes in the
+   meta/recipes-kernel/linux
+   directory of the
+   Source Directory
+   (e.g.
+   poky/meta/recipes-kernel/linux/linux-yocto_4.12.bb
+   ). See the "
+   Using Kernel Metadata in a Recipe
+   " section for more information.
+
+Three kernel types ("standard", "tiny", and "preempt-rt") are supported
+for Linux Yocto kernels:
+
+-  "standard": Includes the generic Linux kernel policy of the Yocto
+   Project linux-yocto kernel recipes. This policy includes, among other
+   things, which file systems, networking options, core kernel features,
+   and debugging and tracing options are supported.
+
+-  "preempt-rt": Applies the ``PREEMPT_RT`` patches and the
+   configuration options required to build a real-time Linux kernel.
+   This kernel type inherits from the "standard" kernel type.
+
+-  "tiny": Defines a bare minimum configuration meant to serve as a base
+   for very small Linux kernels. The "tiny" kernel type is independent
+   from the "standard" configuration. Although the "tiny" kernel type
+   does not currently include any source changes, it might in the
+   future.
+
+For any given kernel type, the Metadata is defined by the ``.scc`` (e.g.
+``standard.scc``). Here is a partial listing for the ``standard.scc``
+file, which is found in the ``ktypes/standard`` directory of the
+``yocto-kernel-cache`` Git repository: # Include this kernel type
+fragment to get the standard features and # configuration values. #
+Note: if only the features are desired, but not the configuration # then
+this should be included as: # include ktypes/standard/standard.scc nocfg
+# if no chained configuration is desired, include it as: # include
+ktypes/standard/standard.scc nocfg inherit include ktypes/base/base.scc
+branch standard kconf non-hardware standard.cfg include
+features/kgdb/kgdb.scc . . . include cfg/net/ip6_nf.scc include
+cfg/net/bridge.scc include cfg/systemd.scc include
+features/rfkill/rfkill.scc
+
+As with any ``.scc`` file, a kernel type definition can aggregate other
+``.scc`` files with ``include`` commands. These definitions can also
+directly pull in configuration fragments and patches with the ``kconf``
+and ``patch`` commands, respectively.
+
+.. note::
+
+   It is not strictly necessary to create a kernel type
+   .scc
+   file. The Board Support Package (BSP) file can implicitly define the
+   kernel type using a
+   define
+   KTYPE
+   myktype
+   line. See the "
+   BSP Descriptions
+   " section for more information.
+
+BSP Descriptions
+----------------
+
+BSP descriptions (i.e. ``*.scc`` files) combine kernel types with
+hardware-specific features. The hardware-specific Metadata is typically
+defined independently in the BSP layer, and then aggregated with each
+supported kernel type.
+
+.. note::
+
+   For BSPs supported by the Yocto Project, the BSP description files
+   are located in the
+   bsp
+   directory of the
+   yocto-kernel-cache
+   repository organized under the "Yocto Linux Kernel" heading in the
+   Yocto Project Source Repositories
+   .
+
+This section overviews the BSP description structure, the aggregation
+concepts, and presents a detailed example using a BSP supported by the
+Yocto Project (i.e. BeagleBone Board). For complete information on BSP
+layer file hierarchy, see the `Yocto Project Board Support Package (BSP)
+Developer's Guide <&YOCTO_DOCS_BSP_URL;>`__.
+
+.. _bsp-description-file-overview:
+
+Overview
+~~~~~~~~
+
+For simplicity, consider the following root BSP layer description files
+for the BeagleBone board. These files employ both a structure and naming
+convention for consistency. The naming convention for the file is as
+follows: bsp_root_name-kernel_type.scc Here are some example root layer
+BSP filenames for the BeagleBone Board BSP, which is supported by the
+Yocto Project: beaglebone-standard.scc beaglebone-preempt-rt.scc Each
+file uses the root name (i.e "beaglebone") BSP name followed by the
+kernel type.
+
+Examine the ``beaglebone-standard.scc`` file: define KMACHINE beaglebone
+define KTYPE standard define KARCH arm include
+ktypes/standard/standard.scc branch beaglebone include beaglebone.scc #
+default policy for standard kernels include
+features/latencytop/latencytop.scc include
+features/profiling/profiling.scc Every top-level BSP description file
+should define the ```KMACHINE`` <&YOCTO_DOCS_REF_URL;#var-KMACHINE>`__,
+```KTYPE`` <&YOCTO_DOCS_REF_URL;#var-KTYPE>`__, and
+```KARCH`` <&YOCTO_DOCS_REF_URL;#var-KARCH>`__ variables. These
+variables allow the OpenEmbedded build system to identify the
+description as meeting the criteria set by the recipe being built. This
+example supports the "beaglebone" machine for the "standard" kernel and
+the "arm" architecture.
+
+Be aware that a hard link between the ``KTYPE`` variable and a kernel
+type description file does not exist. Thus, if you do not have the
+kernel type defined in your kernel Metadata as it is here, you only need
+to ensure that the
+```LINUX_KERNEL_TYPE`` <&YOCTO_DOCS_REF_URL;#var-LINUX_KERNEL_TYPE>`__
+variable in the kernel recipe and the ``KTYPE`` variable in the BSP
+description file match.
+
+To separate your kernel policy from your hardware configuration, you
+include a kernel type (``ktype``), such as "standard". In the previous
+example, this is done using the following: include
+ktypes/standard/standard.scc This file aggregates all the configuration
+fragments, patches, and features that make up your standard kernel
+policy. See the "`Kernel Types <#kernel-types>`__" section for more
+information.
+
+To aggregate common configurations and features specific to the kernel
+for mybsp, use the following: include mybsp.scc You can see that in the
+BeagleBone example with the following: include beaglebone.scc For
+information on how to break a complete ``.config`` file into the various
+configuration fragments, see the "`Creating Configuration
+Fragments <#creating-config-fragments>`__" section.
+
+Finally, if you have any configurations specific to the hardware that
+are not in a ``*.scc`` file, you can include them as follows: kconf
+hardware mybsp-extra.cfg The BeagleBone example does not include these
+types of configurations. However, the Malta 32-bit board does
+("mti-malta32"). Here is the ``mti-malta32-le-standard.scc`` file:
+define KMACHINE mti-malta32-le define KMACHINE qemumipsel define KTYPE
+standard define KARCH mips include ktypes/standard/standard.scc branch
+mti-malta32 include mti-malta32.scc kconf hardware mti-malta32-le.cfg
+
+.. _bsp-description-file-example-minnow:
+
+Example
+~~~~~~~
+
+Many real-world examples are more complex. Like any other ``.scc`` file,
+BSP descriptions can aggregate features. Consider the Minnow BSP
+definition given the ``linux-yocto-4.4`` branch of the
+``yocto-kernel-cache`` (i.e.
+``yocto-kernel-cache/bsp/minnow/minnow.scc``):
+
+.. note::
+
+   Although the Minnow Board BSP is unused, the Metadata remains and is
+   being used here just as an example.
+
+include cfg/x86.scc include features/eg20t/eg20t.scc include
+cfg/dmaengine.scc include features/power/intel.scc include cfg/efi.scc
+include features/usb/ehci-hcd.scc include features/usb/ohci-hcd.scc
+include features/usb/usb-gadgets.scc include
+features/usb/touchscreen-composite.scc include cfg/timer/hpet.scc
+include features/leds/leds.scc include features/spi/spidev.scc include
+features/i2c/i2cdev.scc include features/mei/mei-txe.scc # Earlyprintk
+and port debug requires 8250 kconf hardware cfg/8250.cfg kconf hardware
+minnow.cfg kconf hardware minnow-dev.cfg
+
+The ``minnow.scc`` description file includes a hardware configuration
+fragment (``minnow.cfg``) specific to the Minnow BSP as well as several
+more general configuration fragments and features enabling hardware
+found on the machine. This ``minnow.scc`` description file is then
+included in each of the three "minnow" description files for the
+supported kernel types (i.e. "standard", "preempt-rt", and "tiny").
+Consider the "minnow" description for the "standard" kernel type (i.e.
+``minnow-standard.scc``: define KMACHINE minnow define KTYPE standard
+define KARCH i386 include ktypes/standard include minnow.scc # Extra
+minnow configs above the minimal defined in minnow.scc include
+cfg/efi-ext.scc include features/media/media-all.scc include
+features/sound/snd_hda_intel.scc # The following should really be in
+standard.scc # USB live-image support include cfg/usb-mass-storage.scc
+include cfg/boot-live.scc # Basic profiling include
+features/latencytop/latencytop.scc include
+features/profiling/profiling.scc # Requested drivers that don't have an
+existing scc kconf hardware minnow-drivers-extra.cfg The ``include``
+command midway through the file includes the ``minnow.scc`` description
+that defines all enabled hardware for the BSP that is common to all
+kernel types. Using this command significantly reduces duplication.
+
+Now consider the "minnow" description for the "tiny" kernel type (i.e.
+``minnow-tiny.scc``): define KMACHINE minnow define KTYPE tiny define
+KARCH i386 include ktypes/tiny include minnow.scc As you might expect,
+the "tiny" description includes quite a bit less. In fact, it includes
+only the minimal policy defined by the "tiny" kernel type and the
+hardware-specific configuration required for booting the machine along
+with the most basic functionality of the system as defined in the base
+"minnow" description file.
+
+Notice again the three critical variables:
+```KMACHINE`` <&YOCTO_DOCS_REF_URL;#var-KMACHINE>`__,
+```KTYPE`` <&YOCTO_DOCS_REF_URL;#var-KTYPE>`__, and
+```KARCH`` <&YOCTO_DOCS_REF_URL;#var-KARCH>`__. Of these variables, only
+``KTYPE`` has changed to specify the "tiny" kernel type.
+
+Kernel Metadata Location
+========================
+
+Kernel Metadata always exists outside of the kernel tree either defined
+in a kernel recipe (recipe-space) or outside of the recipe. Where you
+choose to define the Metadata depends on what you want to do and how you
+intend to work. Regardless of where you define the kernel Metadata, the
+syntax used applies equally.
+
+If you are unfamiliar with the Linux kernel and only wish to apply a
+configuration and possibly a couple of patches provided to you by
+others, the recipe-space method is recommended. This method is also a
+good approach if you are working with Linux kernel sources you do not
+control or if you just do not want to maintain a Linux kernel Git
+repository on your own. For partial information on how you can define
+kernel Metadata in the recipe-space, see the "`Modifying an Existing
+Recipe <#modifying-an-existing-recipe>`__" section.
+
+Conversely, if you are actively developing a kernel and are already
+maintaining a Linux kernel Git repository of your own, you might find it
+more convenient to work with kernel Metadata kept outside the
+recipe-space. Working with Metadata in this area can make iterative
+development of the Linux kernel more efficient outside of the BitBake
+environment.
+
+Recipe-Space Metadata
+---------------------
+
+When stored in recipe-space, the kernel Metadata files reside in a
+directory hierarchy below
+```FILESEXTRAPATHS`` <&YOCTO_DOCS_REF_URL;#var-FILESEXTRAPATHS>`__. For
+a linux-yocto recipe or for a Linux kernel recipe derived by copying and
+modifying
+``oe-core/meta-skeleton/recipes-kernel/linux/linux-yocto-custom.bb`` to
+a recipe in your layer, ``FILESEXTRAPATHS`` is typically set to
+``${``\ ```THISDIR`` <&YOCTO_DOCS_REF_URL;#var-THISDIR>`__\ ``}/${``\ ```PN`` <&YOCTO_DOCS_REF_URL;#var-PN>`__\ ``}``.
+See the "`Modifying an Existing
+Recipe <#modifying-an-existing-recipe>`__" section for more information.
+
+Here is an example that shows a trivial tree of kernel Metadata stored
+in recipe-space within a BSP layer: meta-my_bsp_layer/ \`--
+recipes-kernel \`-- linux \`-- linux-yocto \|-- bsp-standard.scc \|--
+bsp.cfg \`-- standard.cfg
+
+When the Metadata is stored in recipe-space, you must take steps to
+ensure BitBake has the necessary information to decide what files to
+fetch and when they need to be fetched again. It is only necessary to
+specify the ``.scc`` files on the
+```SRC_URI`` <&YOCTO_DOCS_REF_URL;#var-SRC_URI>`__. BitBake parses them
+and fetches any files referenced in the ``.scc`` files by the
+``include``, ``patch``, or ``kconf`` commands. Because of this, it is
+necessary to bump the recipe ```PR`` <&YOCTO_DOCS_REF_URL;#var-PR>`__
+value when changing the content of files not explicitly listed in the
+``SRC_URI``.
+
+If the BSP description is in recipe space, you cannot simply list the
+``*.scc`` in the ``SRC_URI`` statement. You need to use the following
+form from your kernel append file: SRC_URI_append_myplatform = " \\
+file://myplatform;type=kmeta;destsuffix=myplatform \\ "
+
+Metadata Outside the Recipe-Space
+---------------------------------
+
+When stored outside of the recipe-space, the kernel Metadata files
+reside in a separate repository. The OpenEmbedded build system adds the
+Metadata to the build as a "type=kmeta" repository through the
+```SRC_URI`` <&YOCTO_DOCS_REF_URL;#var-SRC_URI>`__ variable. As an
+example, consider the following ``SRC_URI`` statement from the
+``linux-yocto_4.12.bb`` kernel recipe: SRC_URI =
+"git://git.yoctoproject.org/linux-yocto-4.12.git;name=machine;branch=${KBRANCH};
+\\
+git://git.yoctoproject.org/yocto-kernel-cache;type=kmeta;name=meta;branch=yocto-4.12;destsuffix=${KMETA}"
+``${KMETA}``, in this context, is simply used to name the directory into
+which the Git fetcher places the Metadata. This behavior is no different
+than any multi-repository ``SRC_URI`` statement used in a recipe (e.g.
+see the previous section).
+
+You can keep kernel Metadata in a "kernel-cache", which is a directory
+containing configuration fragments. As with any Metadata kept outside
+the recipe-space, you simply need to use the ``SRC_URI`` statement with
+the "type=kmeta" attribute. Doing so makes the kernel Metadata available
+during the configuration phase.
+
+If you modify the Metadata, you must not forget to update the ``SRCREV``
+statements in the kernel's recipe. In particular, you need to update the
+``SRCREV_meta`` variable to match the commit in the ``KMETA`` branch you
+wish to use. Changing the data in these branches and not updating the
+``SRCREV`` statements to match will cause the build to fetch an older
+commit.
+
+Organizing Your Source
+======================
+
+Many recipes based on the ``linux-yocto-custom.bb`` recipe use Linux
+kernel sources that have only a single branch - "master". This type of
+repository structure is fine for linear development supporting a single
+machine and architecture. However, if you work with multiple boards and
+architectures, a kernel source repository with multiple branches is more
+efficient. For example, suppose you need a series of patches for one
+board to boot. Sometimes, these patches are works-in-progress or
+fundamentally wrong, yet they are still necessary for specific boards.
+In these situations, you most likely do not want to include these
+patches in every kernel you build (i.e. have the patches as part of the
+lone "master" branch). It is situations like these that give rise to
+multiple branches used within a Linux kernel sources Git repository.
+
+Repository organization strategies exist that maximize source reuse,
+remove redundancy, and logically order your changes. This section
+presents strategies for the following cases:
+
+-  Encapsulating patches in a feature description and only including the
+   patches in the BSP descriptions of the applicable boards.
+
+-  Creating a machine branch in your kernel source repository and
+   applying the patches on that branch only.
+
+-  Creating a feature branch in your kernel source repository and
+   merging that branch into your BSP when needed.
+
+The approach you take is entirely up to you and depends on what works
+best for your development model.
+
+Encapsulating Patches
+---------------------
+
+if you are reusing patches from an external tree and are not working on
+the patches, you might find the encapsulated feature to be appropriate.
+Given this scenario, you do not need to create any branches in the
+source repository. Rather, you just take the static patches you need and
+encapsulate them within a feature description. Once you have the feature
+description, you simply include that into the BSP description as
+described in the "`BSP Descriptions <#bsp-descriptions>`__" section.
+
+You can find information on how to create patches and BSP descriptions
+in the "`Patches <#patches>`__" and "`BSP
+Descriptions <#bsp-descriptions>`__" sections.
+
+Machine Branches
+----------------
+
+When you have multiple machines and architectures to support, or you are
+actively working on board support, it is more efficient to create
+branches in the repository based on individual machines. Having machine
+branches allows common source to remain in the "master" branch with any
+features specific to a machine stored in the appropriate machine branch.
+This organization method frees you from continually reintegrating your
+patches into a feature.
+
+Once you have a new branch, you can set up your kernel Metadata to use
+the branch a couple different ways. In the recipe, you can specify the
+new branch as the ``KBRANCH`` to use for the board as follows: KBRANCH =
+"mynewbranch" Another method is to use the ``branch`` command in the BSP
+description: mybsp.scc: define KMACHINE mybsp define KTYPE standard
+define KARCH i386 include standard.scc branch mynewbranch include
+mybsp-hw.scc
+
+If you find yourself with numerous branches, you might consider using a
+hierarchical branching system similar to what the Yocto Linux Kernel Git
+repositories use: common/kernel_type/machine
+
+If you had two kernel types, "standard" and "small" for instance, three
+machines, and common as ``mydir``, the branches in your Git repository
+might look like this: mydir/base mydir/standard/base
+mydir/standard/machine_a mydir/standard/machine_b
+mydir/standard/machine_c mydir/small/base mydir/small/machine_a
+
+This organization can help clarify the branch relationships. In this
+case, ``mydir/standard/machine_a`` includes everything in ``mydir/base``
+and ``mydir/standard/base``. The "standard" and "small" branches add
+sources specific to those kernel types that for whatever reason are not
+appropriate for the other branches.
+
+.. note::
+
+   The "base" branches are an artifact of the way Git manages its data
+   internally on the filesystem: Git will not allow you to use
+   mydir/standard
+   and
+   mydir/standard/machine_a
+   because it would have to create a file and a directory named
+   "standard".
+
+Feature Branches
+----------------
+
+When you are actively developing new features, it can be more efficient
+to work with that feature as a branch, rather than as a set of patches
+that have to be regularly updated. The Yocto Project Linux kernel tools
+provide for this with the ``git merge`` command.
+
+To merge a feature branch into a BSP, insert the ``git merge`` command
+after any ``branch`` commands: mybsp.scc: define KMACHINE mybsp define
+KTYPE standard define KARCH i386 include standard.scc branch mynewbranch
+git merge myfeature include mybsp-hw.scc
+
+.. _scc-reference:
+
+SCC Description File Reference
+==============================
+
+This section provides a brief reference for the commands you can use
+within an SCC description file (``.scc``):
+
+-  ``branch [ref]``: Creates a new branch relative to the current branch
+   (typically ``${KTYPE}``) using the currently checked-out branch, or
+   "ref" if specified.
+
+-  ``define``: Defines variables, such as
+   ```KMACHINE`` <&YOCTO_DOCS_REF_URL;#var-KMACHINE>`__,
+   ```KTYPE`` <&YOCTO_DOCS_REF_URL;#var-KTYPE>`__,
+   ```KARCH`` <&YOCTO_DOCS_REF_URL;#var-KARCH>`__, and
+   ```KFEATURE_DESCRIPTION`` <&YOCTO_DOCS_REF_URL;#var-KFEATURE_DESCRIPTION>`__.
+
+-  ``include SCC_FILE``: Includes an SCC file in the current file. The
+   file is parsed as if you had inserted it inline.
+
+-  ``kconf [hardware|non-hardware] CFG_FILE``: Queues a configuration
+   fragment for merging into the final Linux ``.config`` file.
+
+-  ``git merge GIT_BRANCH``: Merges the feature branch into the current
+   branch.
+
+-  ``patch PATCH_FILE``: Applies the patch to the current Git branch.
+
+.. [1]
+   ``scc`` stands for Series Configuration Control, but the naming has
+   less significance in the current implementation of the tooling than
+   it had in the past. Consider ``scc`` files to be description files.