manuals: add new contributor guide

(From yocto-docs rev: 77f20d1594db42818aac9a7a92865def8fb7ec36)

Signed-off-by: Michael Opdenacker <michael.opdenacker@bootlin.com>
Signed-off-by: Steve Sakoman <steve@sakoman.com>

5 files changed, 1135 insertions, 0 deletions

diff --git a/documentation/contributor-guide/identify-component.rst b/documentation/contributor-guide/identify-component.rst
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+.. SPDX-License-Identifier: CC-BY-SA-2.0-UK
+
+Identify the component
+**********************
+
+The Yocto Project and OpenEmbedded ecosystem is built of :term:`layers <Layer>`
+so the first step is to identify the component where the issue likely lies.
+For example, if you have a hardware issue, it is likely related to the BSP
+you are using and the best place to seek advice would be from the BSP provider
+or :term:`layer`. If the issue is a build/configuration one and a distro is in
+use, they would likely be the first place to ask questions. If the issue is a
+generic one and/or in the core classes or metadata, the core layer or BitBake
+might be the appropriate component.
+
+Each metadata layer being used should contain a ``README`` file and that should
+explain where to report issues, where to send changes and how to contact the
+maintainers.
+
+If the issue is in the core metadata layer (OpenEmbedded-Core) or in BitBake,
+issues can be reported in the :yocto_bugs:`Yocto Project Bugzilla <>`. The
+:yocto_lists:`yocto </g/yocto>` mailing list is a general “catch-all” location
+where questions can be sent if you can’t work out where something should go.
+
+:term:`Poky` is a commonly used “combination” repository where multiple
+components have been combined (:oe_git:`bitbake </bitbake>`,
+:oe_git:`openembedded-core </openembedded-core>`,
+:yocto_git:`meta-yocto </meta-yocto>` and
+:yocto_git:`yocto-docs </yocto-docs>`). Patches should be submitted against the
+appropriate individual component rather than :term:`Poky` itself as detailed in
+the appropriate ``README`` file.
+
diff --git a/documentation/contributor-guide/index.rst b/documentation/contributor-guide/index.rst
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+.. SPDX-License-Identifier: CC-BY-SA-2.0-UK
+
+================================================
+Yocto Project and OpenEmbedded Contributor Guide
+================================================
+
+The Yocto Project and OpenEmbedded are open-source, community-based projects so
+contributions are very welcome, it is how the code evolves and everyone can
+effect change. Contributions take different forms, if you have a fix for an
+issue you’ve run into, a patch is the most appropriate way to contribute it.
+If you run into an issue but don’t have a solution, opening a defect in
+:yocto_bugs:`Bugzilla <>` or asking questions on the mailing lists might be
+more appropriate. This guide intends to point you in the right direction to
+this.
+
+
+.. toctree::
+   :caption: Table of Contents
+   :numbered:
+
+   identify-component
+   report-defect
+   recipe-style-guide
+   submit-changes
+
+.. include:: /boilerplate.rst
diff --git a/documentation/contributor-guide/recipe-style-guide.rst b/documentation/contributor-guide/recipe-style-guide.rst
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+.. SPDX-License-Identifier: CC-BY-SA-2.0-UK
+
+Recipe Style Guide
+******************
+
+Recipe Naming Conventions
+=========================
+
+In general, most recipes should follow the naming convention
+``recipes-category/package/packagename_version.bb``. Recipes for related
+projects may share the same package directory. ``packagename``, ``category``,
+and ``package`` may contain hyphens, but hyphens are not allowed in ``version``.
+
+If the recipe is tracking a Git revision that does not correspond to a released
+version of the software, ``version`` may be ``git`` (e.g. ``packagename_git.bb``)
+
+Version Policy
+==============
+
+Our versions follow the form ``<package epoch>:<package version>-<package revision>``
+or in BitBake variable terms ${:term:`PE`}:${:term:`PV`}-${:term:`PR`}. We
+generally follow the `Debian <https://www.debian.org/doc/debian-policy/ch-controlfields.html#version>`__
+version policy which defines these terms.
+
+In most cases the version :term:`PV` will be set automatically from the recipe
+file name. It is recommended to use released versions of software as these are
+revisions that upstream are expecting people to use.
+
+Package versions should always compare and sort correctly so that upgrades work
+as expected. With conventional versions such as ``1.4`` upgrading ``to 1.5``
+this happens naturally, but some versions don't sort. For example,
+``1.5 Release Candidate 2`` could be written as ``1.5rc2`` but this sorts after
+``1.5``, so upgrades from feeds won't happen correctly.
+
+Instead the tilde (``~``) operator can be used, which sorts before the empty
+string so ``1.5~rc2`` comes before ``1.5``. There is a historical syntax which
+may be found where :term:`PV` is set as a combination of the prior version
+``+`` the pre-release version, for example ``PV=1.4+1.5rc2``. This is a valid
+syntax but the tilde form is preferred.
+
+For version comparisons, the ``opkg-compare-versions`` program from
+``opkg-utils`` can be useful when attempting to determine how two version
+numbers compare to each other. Our definitive version comparison algorithm is
+the one within bitbake which aims to match those of the package managers and
+Debian policy closely.
+
+When a recipe references a git revision that does not correspond to a released
+version of software (e.g. is not a tagged version), the :term:`PV` variable
+should include the Git revision using the following to make the
+version clear::
+
+    PV = "<version>+git${SRCPV}"
+
+In this case, ``<version>`` should be the most recently released version of the
+software from the current source revision (``git describe`` can be useful for
+determining this). Whilst not recommended for published layers, this format is
+also useful when using :term:`AUTOREV` to set the recipe to increment source
+control revisions automatically, which can be useful during local development.
+
+Version Number Changes
+======================
+
+The :term:`PR` variable is used to indicate different revisions of a recipe
+that reference the same upstream source version. It can be used to force a
+new version of a package to be installed onto a device from a package feed.
+These once had to be set manually but in most cases these can now be set and
+incremented automatically by a PR Server connected with a package feed.
+
+When :term:`PV` increases, any existing :term:`PR` value can and should be
+removed.
+
+If :term:`PV` changes in such a way that it does not increase with respect to
+the previous value, you need to increase :term:`PE` to ensure package managers
+will upgrade it correctly. If unset you should set :term:`PE` to "1" since
+the default of empty is easily confused with "0" depending on the package
+manager. :term:`PE` can only have an integer value.
+
+Recipe formatting
+=================
+
+Variable Formatting
+-------------------
+
+-  Variable assignment should a space around each side of the operator, e.g.
+   ``FOO = "bar"``, not ``FOO="bar"``.
+
+-  Double quotes should be used on the right-hand side of the assignment,
+   e.g. ``FOO = "bar"`` not ``FOO = 'bar'``
+
+-  Spaces should be used for indenting variables, with 4 spaces per tab
+
+-  Long variables should be split over multiple lines when possible by using
+   the continuation character (``\``)
+
+-  When splitting a long variable over multiple lines, all continuation lines
+   should be indented (with spaces) to align with the start of the quote on the
+   first line::
+
+       FOO = "this line is \
+              long \
+              "
+
+   Instead of::
+
+       FOO = "this line is \
+       long \
+       "
+
+Python Function formatting
+--------------------------
+
+-  Spaces must be used for indenting Python code, with 4 spaces per tab
+
+Shell Function formatting
+-------------------------
+
+-  The formatting of shell functions should be consistent within layers.
+   Some use tabs, some use spaces.
+
+Recipe metadata
+===============
+
+Required Variables
+------------------
+
+The following variables should be included in all recipes:
+
+-  :term:`SUMMARY`: a one line description of the upstream project
+
+-  :term:`DESCRIPTION`: an extended description of the upstream project,
+   possibly with multiple lines. If no reasonable description can be written,
+   this may be omitted as it defaults to :term:`SUMMARY`.
+
+-  :term:`HOMEPAGE`: the URL to the upstream projects homepage.
+
+-  :term:`BUGTRACKER`: the URL upstream projects bug tracking website,
+   if applicable.
+
+Recipe Ordering
+---------------
+
+When a variable is defined in recipes and classes, variables should follow the
+general order when possible:
+
+-  :term:`SUMMARY`
+-  :term:`DESCRIPTION`
+-  :term:`HOMEPAGE`
+-  :term:`BUGTRACKER`
+-  :term:`SECTION`
+-  :term:`LICENSE`
+-  :term:`LIC_FILES_CHKSUM`
+-  :term:`DEPENDS`
+-  :term:`PROVIDES`
+-  :term:`PV`
+-  :term:`SRC_URI`
+-  :term:`SRCREV`
+-  :term:`S`
+-  ``inherit ...``
+-  :term:`PACKAGECONFIG`
+-  Build class specific variables such as ``EXTRA_QMAKEVARS_POST`` and :term:`EXTRA_OECONF`
+-  Tasks such as :ref:`ref-tasks-configure`
+-  :term:`PACKAGE_ARCH`
+-  :term:`PACKAGES`
+-  :term:`FILES`
+-  :term:`RDEPENDS`
+-  :term:`RRECOMMENDS`
+-  :term:`RSUGGESTS`
+-  :term:`RPROVIDES`
+-  :term:`RCONFLICTS`
+-  :term:`BBCLASSEXTEND`
+
+There are some cases where ordering is important and these cases would override
+this default order. Examples include:
+
+-  :term:`PACKAGE_ARCH` needing to be set before ``inherit packagegroup``
+
+Tasks should be ordered based on the order they generally execute. For commonly
+used tasks this would be:
+
+-  :ref:`ref-tasks-fetch`
+-  :ref:`ref-tasks-unpack`
+-  :ref:`ref-tasks-patch`
+-  :ref:`ref-tasks-prepare_recipe_sysroot`
+-  :ref:`ref-tasks-configure`
+-  :ref:`ref-tasks-compile`
+-  :ref:`ref-tasks-install`
+-  :ref:`ref-tasks-populate_sysroot`
+-  :ref:`ref-tasks-package`
+
+Custom tasks should be sorted similarly.
+
+Package specific variables are typically grouped together, e.g.::
+
+    RDEPENDS:${PN} = “foo”
+    RDEPENDS:${PN}-libs = “bar”
+
+    RRECOMMENDS:${PN} = “one”
+    RRECOMMENDS:${PN}-libs = “two”
+
+Recipe License Fields
+---------------------
+
+Recipes need to define both the :term:`LICENSE` and
+:term:`LIC_FILES_CHKSUM` variables:
+
+-  :term:`LICENSE`: This variable specifies the license for the software.
+   If you do not know the license under which the software you are
+   building is distributed, you should go to the source code and look
+   for that information. Typical files containing this information
+   include ``COPYING``, :term:`LICENSE`, and ``README`` files. You could
+   also find the information near the top of a source file. For example,
+   given a piece of software licensed under the GNU General Public
+   License version 2, you would set :term:`LICENSE` as follows::
+
+      LICENSE = "GPL-2.0-only"
+
+   The licenses you specify within :term:`LICENSE` can have any name as long
+   as you do not use spaces, since spaces are used as separators between
+   license names. For standard licenses, use the names of the files in
+   ``meta/files/common-licenses/`` or the :term:`SPDXLICENSEMAP` flag names
+   defined in ``meta/conf/licenses.conf``.
+
+-  :term:`LIC_FILES_CHKSUM`: The OpenEmbedded build system uses this
+   variable to make sure the license text has not changed. If it has,
+   the build produces an error and it affords you the chance to figure
+   it out and correct the problem.
+
+   You need to specify all applicable licensing files for the software.
+   At the end of the configuration step, the build process will compare
+   the checksums of the files to be sure the text has not changed. Any
+   differences result in an error with the message containing the
+   current checksum. For more explanation and examples of how to set the
+   :term:`LIC_FILES_CHKSUM` variable, see the
+   ":ref:`dev-manual/licenses:tracking license changes`" section.
+
+   To determine the correct checksum string, you can list the
+   appropriate files in the :term:`LIC_FILES_CHKSUM` variable with incorrect
+   md5 strings, attempt to build the software, and then note the
+   resulting error messages that will report the correct md5 strings.
+   See the ":ref:`dev-manual/new-recipe:fetching code`" section for
+   additional information.
+
+   Here is an example that assumes the software has a ``COPYING`` file::
+
+      LIC_FILES_CHKSUM = "file://COPYING;md5=xxx"
+
+   When you try to build the
+   software, the build system will produce an error and give you the
+   correct string that you can substitute into the recipe file for a
+   subsequent build.
+
+Tips and Guidelines for Writing Recipes
+---------------------------------------
+
+-  Use :term:`BBCLASSEXTEND` instead of creating separate recipes such as ``-native``
+   and ``-nativesdk`` ones, whenever possible. This avoids having to maintain multiple
+   recipe files at the same time.
diff --git a/documentation/contributor-guide/report-defect.rst b/documentation/contributor-guide/report-defect.rst
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+.. SPDX-License-Identifier: CC-BY-SA-2.0-UK
+
+Reporting a Defect Against the Yocto Project and OpenEmbedded
+**************************************************************
+
+You can use the Yocto Project instance of
+`Bugzilla <https://www.bugzilla.org/about/>`__ to submit a defect (bug)
+against BitBake, OpenEmbedded-Core, against any other Yocto Project component
+or for tool issues. For additional information on this implementation of
+Bugzilla see the ":ref:`Yocto Project Bugzilla <resources-bugtracker>`" section
+in the Yocto Project Reference Manual. For more detail on any of the following
+steps, see the Yocto Project
+:yocto_wiki:`Bugzilla wiki page </Bugzilla_Configuration_and_Bug_Tracking>`.
+
+Use the following general steps to submit a bug:
+
+#.  Open the Yocto Project implementation of :yocto_bugs:`Bugzilla <>`.
+
+#.  Click "File a Bug" to enter a new bug.
+
+#.  Choose the appropriate "Classification", "Product", and "Component"
+    for which the bug was found. Bugs for the Yocto Project fall into
+    one of several classifications, which in turn break down into
+    several products and components. For example, for a bug against the
+    ``meta-intel`` layer, you would choose "Build System, Metadata &
+    Runtime", "BSPs", and "bsps-meta-intel", respectively.
+
+#.  Choose the "Version" of the Yocto Project for which you found the
+    bug (e.g. &DISTRO;).
+
+#.  Determine and select the "Severity" of the bug. The severity
+    indicates how the bug impacted your work.
+
+#.  Choose the "Hardware" that the bug impacts.
+
+#.  Choose the "Architecture" that the bug impacts.
+
+#.  Choose a "Documentation change" item for the bug. Fixing a bug might
+    or might not affect the Yocto Project documentation. If you are
+    unsure of the impact to the documentation, select "Don't Know".
+
+#.  Provide a brief "Summary" of the bug. Try to limit your summary to
+    just a line or two and be sure to capture the essence of the bug.
+
+#.  Provide a detailed "Description" of the bug. You should provide as
+    much detail as you can about the context, behavior, output, and so
+    forth that surrounds the bug. You can even attach supporting files
+    for output from logs by using the "Add an attachment" button.
+
+#.  Click the "Submit Bug" button submit the bug. A new Bugzilla number
+    is assigned to the bug and the defect is logged in the bug tracking
+    system.
+
+Once you file a bug, the bug is processed by the Yocto Project Bug
+Triage Team and further details concerning the bug are assigned (e.g.
+priority and owner). You are the "Submitter" of the bug and any further
+categorization, progress, or comments on the bug result in Bugzilla
+sending you an automated email concerning the particular change or
+progress to the bug.
+
+There are no guarantees about if or when a bug might be worked on since an
+open-source project has no dedicated engineering resources. However, the
+project does have a good track record of resolving common issues over the
+medium and long term. We do encourage people to file bugs so issues are
+at least known about. It helps other users when they find somebody having
+the same issue as they do, and an issue that is unknown is much less likely
+to ever be fixed!
diff --git a/documentation/contributor-guide/submit-changes.rst b/documentation/contributor-guide/submit-changes.rst
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+.. SPDX-License-Identifier: CC-BY-SA-2.0-UK
+
+Contributing Changes to a Component
+************************************
+
+Contributions to the Yocto Project and OpenEmbedded are very welcome.
+Because the system is extremely configurable and flexible, we recognize
+that developers will want to extend, configure or optimize it for their
+specific uses.
+
+.. _ref-why-mailing-lists:
+
+Contributing through mailing lists --- Why not using web-based workflows?
+=========================================================================
+
+Both Yocto Project and OpenEmbedded have many key components that are
+maintained by patches being submitted on mailing lists. We appreciate this
+approach does look a little old fashioned when other workflows are available
+through web technology such as GitHub, GitLab and others. Since we are often
+asked this question, we’ve decided to document the reasons for using mailing
+lists.
+
+One significant factor is that we value peer review. When a change is proposed
+to many of the core pieces of the project, it helps to have many eyes of review
+go over them. Whilst there is ultimately one maintainer who needs to make the
+final call on accepting or rejecting a patch, the review is made by many eyes
+and the exact people reviewing it are likely unknown to the maintainer. It is
+often the surprise reviewer that catches the most interesting issues!
+
+This is in contrast to the "GitHub" style workflow where either just a
+maintainer makes that review, or review is specifically requested from
+nominated people. We believe there is significant value added to the codebase
+by this peer review and that moving away from mailing lists would be to the
+detriment of our code.
+
+We also need to acknowledge that many of our developers are used to this
+mailing list workflow and have worked with it for years, with tools and
+processes built around it. Changing away from this would result in a loss
+of key people from the project, which would again be to its detriment.
+
+The projects are acutely aware that potential new contributors find the
+mailing list approach off-putting and would prefer a web-based GUI.
+Since we don’t believe that can work for us, the project is aiming to ensure
+`patchwork <https://patchwork.yoctoproject.org/>`__ is available to help track
+patch status and also looking at how tooling can provide more feedback to users
+about patch status. We are looking at improving tools such as ``patchtest`` to
+test user contributions before they hit the mailing lists and also at better
+documenting how to use such workflows since we recognise that whilst this was
+common knowledge a decade ago, it might not be as familiar now.
+
+Preparing Changes for Submission
+================================
+
+Set up Git
+----------
+
+The first thing to do is to install Git packages. Here is an example
+on Debian and Ubuntu::
+
+   sudo aptitude install git-core git-email
+
+Then, you need to set a name and e-mail address that Git will
+use to identify your commits::
+
+   git config --global user.name "Ada Lovelace"
+   git config --global user.email "ada.lovelace@gmail.com"
+
+Clone the Git repository for the component to modify
+----------------------------------------------------
+
+After identifying the component to modify as described in the
+":doc:`../contributor-guide/identify-component`" section, clone the
+corresponding Git repository. Here is an example for OpenEmbedded-Core::
+
+  git clone https://git.openembedded.org/openembedded-core
+  cd openembedded-core
+
+Create a new branch
+-------------------
+
+Then, create a new branch in your local Git repository
+for your changes, starting from the reference branch in the upstream
+repository (often called ``master``)::
+
+   $ git checkout <ref-branch>
+   $ git checkout -b my-changes
+
+If you have completely unrelated sets of changes to submit, you should even
+create one branch for each set.
+
+Implement and commit changes
+----------------------------
+
+In each branch, you should group your changes into small, controlled and
+isolated ones. Keeping changes small and isolated aids review, makes
+merging/rebasing easier and keeps the change history clean should anyone need
+to refer to it in future.
+
+To this purpose, you should create *one Git commit per change*,
+corresponding to each of the patches you will eventually submit.
+See `further guidance <https://www.kernel.org/doc/html/latest/process/submitting-patches.html#separate-your-changes>`__
+in the Linux kernel documentation if needed.
+
+For example, when you intend to add multiple new recipes, each recipe
+should be added in a separate commit. For upgrades to existing recipes,
+the previous version should usually be deleted as part of the same commit
+to add the upgraded version.
+
+#. *Stage Your Changes:* Stage your changes by using the ``git add``
+   command on each file you modified. If you want to stage all the
+   files you modified, you can even use the ``git add -A`` command.
+
+#. *Commit Your Changes:* This is when you can create separate commits. For
+   each commit to create, use the ``git commit -s`` command with the files
+   or directories you want to include in the commit::
+
+      $ git commit -s file1 file2 dir1 dir2 ...
+
+   To include **a**\ ll staged files::
+
+      $ git commit -sa
+
+   -  The ``-s`` option of ``git commit`` adds a "Signed-off-by:" line
+      to your commit message. There is the same requirement for contributing
+      to the Linux kernel. Adding such a line signifies that you, the
+      submitter, have agreed to the `Developer's Certificate of Origin 1.1
+      <https://www.kernel.org/doc/html/latest/process/submitting-patches.html#sign-your-work-the-developer-s-certificate-of-origin>`__
+      as follows:
+
+      .. code-block:: none
+
+         Developer's Certificate of Origin 1.1
+
+         By making a contribution to this project, I certify that:
+
+         (a) The contribution was created in whole or in part by me and I
+             have the right to submit it under the open source license
+             indicated in the file; or
+
+         (b) The contribution is based upon previous work that, to the best
+             of my knowledge, is covered under an appropriate open source
+             license and I have the right under that license to submit that
+             work with modifications, whether created in whole or in part
+             by me, under the same open source license (unless I am
+             permitted to submit under a different license), as indicated
+             in the file; or
+
+         (c) The contribution was provided directly to me by some other
+             person who certified (a), (b) or (c) and I have not modified
+             it.
+
+         (d) I understand and agree that this project and the contribution
+             are public and that a record of the contribution (including all
+             personal information I submit with it, including my sign-off) is
+             maintained indefinitely and may be redistributed consistent with
+             this project or the open source license(s) involved.
+
+   -  Provide a single-line summary of the change and, if more
+      explanation is needed, provide more detail in the body of the
+      commit. This summary is typically viewable in the "shortlist" of
+      changes. Thus, providing something short and descriptive that
+      gives the reader a summary of the change is useful when viewing a
+      list of many commits. You should prefix this short description
+      with the recipe name (if changing a recipe), or else with the
+      short form path to the file being changed.
+
+      .. note::
+
+         To find a suitable prefix for the commit summary, a good idea
+         is to look for prefixes used in previous commits touching the
+         same files or directories::
+
+            git log --oneline <paths>
+
+   -  For the body of the commit message, provide detailed information
+      that describes what you changed, why you made the change, and the
+      approach you used. It might also be helpful if you mention how you
+      tested the change. Provide as much detail as you can in the body
+      of the commit message.
+
+      .. note::
+
+         If the single line summary is enough to describe a simple
+         change, the body of the commit message can be left empty.
+
+   -  If the change addresses a specific bug or issue that is associated
+      with a bug-tracking ID, include a reference to that ID in your
+      detailed description. For example, the Yocto Project uses a
+      specific convention for bug references --- any commit that addresses
+      a specific bug should use the following form for the detailed
+      description. Be sure to use the actual bug-tracking ID from
+      Bugzilla for bug-id::
+
+         Fixes [YOCTO #bug-id]
+
+         detailed description of change
+
+#. *Crediting contributors:* By using the ``git commit --amend`` command,
+   you can add some tags to the commit description to credit other contributors
+   to the change:
+
+   -  ``Reported-by``: name and email of a person reporting a bug
+      that your commit is trying to fix. This is a good practice
+      to encourage people to go on reporting bugs and let them
+      know that their reports are taken into account.
+
+   -  ``Suggested-by``: name and email of a person to credit for the
+      idea of making the change.
+
+   -  ``Tested-by``, ``Reviewed-by``: name and email for people having
+      tested your changes or reviewed their code. These fields are
+      usually added by the maintainer accepting a patch, or by
+      yourself if you submitted your patches to early reviewers,
+      or are submitting an unmodified patch again as part of a
+      new iteration of your patch series.
+
+   -  ``CC:`` Name and email of people you want to send a copy
+      of your changes to. This field will be used by ``git send-email``.
+
+   See `more guidance about using such tags
+   <https://www.kernel.org/doc/html/latest/process/submitting-patches.html#using-reported-by-tested-by-reviewed-by-suggested-by-and-fixes>`__
+   in the Linux kernel documentation.
+
+Creating Patches
+================
+
+Here is the general procedure on how to create patches to be sent through email:
+
+#. *Describe the Changes in your Branch:* If you have more than one commit
+   in your branch, it's recommended to provide a cover letter describing
+   the series of patches you are about to send.
+
+   For this purpose, a good solution is to store the cover letter contents
+   in the branch itself::
+
+      git branch --edit-description
+
+   This will open a text editor to fill in the description for your
+   changes. This description can be updated when necessary and will
+   be used by Git to create the cover letter together with the patches.
+
+   It is recommended to start this description with a title line which
+   will serve a the subject line for the cover letter.
+
+#. *Generate Patches for your Branch:* The ``git format-patch`` command will
+   generate patch files for each of the commits in your branch. You need
+   to pass the reference branch your branch starts from.
+
+   If you branch didn't need a description in the previous step::
+
+      $ git format-patch <ref-branch>
+
+   If you filled a description for your branch, you will want to generate
+   a cover letter too::
+
+      $ git format-patch --cover-letter --cover-from-description=auto <ref-branch>
+
+   After the command is run, the current directory contains numbered
+   ``.patch`` files for the commits in your branch. If you have a cover
+   letter, it will be in the ``0000-cover-letter.patch``.
+
+   .. note::
+
+      The ``--cover-from-description=auto`` option makes ``git format-patch``
+      use the first paragraph of the branch description as the cover
+      letter title. Another possibility, which is easier to remember, is to pass
+      only the ``--cover-letter`` option, but you will have to edit the
+      subject line manually every time you generate the patches.
+
+      See the `git format-patch manual page <https://git-scm.com/docs/git-format-patch>`__
+      for details.
+
+#. *Review each of the Patch Files:* This final review of the patches
+   before sending them often allows to view your changes from a different
+   perspective and discover defects such as typos, spacing issues or lines
+   or even files that you didn't intend to modify. This review should
+   include the cover letter patch too.
+
+   If necessary, rework your commits as described in
+   ":ref:`contributor-guide/submit-changes:taking patch review into account`".
+
+Sending the Patches via Email
+=============================
+
+Using Git to Send Patches
+-------------------------
+
+To submit patches through email, it is very important that you send them
+without any whitespace or HTML formatting that either you or your mailer
+introduces. The maintainer that receives your patches needs to be able
+to save and apply them directly from your emails, using the ``git am``
+command.
+
+Using the ``git send-email`` command is the only error-proof way of sending
+your patches using email since there is no risk of compromising whitespace
+in the body of the message, which can occur when you use your own mail
+client. It will also properly include your patches as *inline attachments*,
+which is not easy to do with standard e-mail clients without breaking lines.
+If you used your regular e-mail client and shared your patches as regular
+attachments, reviewers wouldn't be able to quote specific sections of your
+changes and make comments about them.
+
+Setting up Git to Send Email
+----------------------------
+
+The ``git send-email`` command can send email by using a local or remote
+Mail Transport Agent (MTA) such as ``msmtp``, ``sendmail``, or
+through a direct SMTP configuration in your Git ``~/.gitconfig`` file.
+
+Here are the settings for letting ``git send-email`` send e-mail through your
+regular STMP server, using a Google Mail account as an example::
+
+   git config --global sendemail.smtpserver smtp.gmail.com
+   git config --global sendemail.smtpserverport 587
+   git config --global sendemail.smtpencryption tls
+   git config --global sendemail.smtpuser ada.lovelace@gmail.com
+   git config --global sendemail.smtppass = XXXXXXXX
+
+These settings will appear in the ``.gitconfig`` file in your home directory.
+
+If you neither can use a local MTA nor SMTP,  make sure you use an email client
+that does not touch the message (turning spaces in tabs, wrapping lines, etc.).
+A good mail client to do so is Pine (or Alpine) or Mutt. For more
+information about suitable clients, see `Email clients info for Linux
+<https://www.kernel.org/doc/html/latest/process/email-clients.html>`__
+in the Linux kernel sources.
+
+If you use such clients, just include the patch in the body of your email.
+
+Finding a Suitable Mailing List
+-------------------------------
+
+You should send patches to the appropriate mailing list so that they can be
+reviewed by the right contributors and merged by the appropriate maintainer.
+The specific mailing list you need to use depends on the location of the code
+you are changing.
+
+If people have concerns with any of the patches, they will usually voice
+their concern over the mailing list. If patches do not receive any negative
+reviews, the maintainer of the affected layer typically takes them, tests them,
+and then based on successful testing, merges them.
+
+In general, each component (e.g. layer) should have a ``README`` file
+that indicates where to send the changes and which process to follow.
+
+The "poky" repository, which is the Yocto Project's reference build
+environment, is a hybrid repository that contains several individual
+pieces (e.g. BitBake, Metadata, documentation, and so forth) built using
+the combo-layer tool. The upstream location used for submitting changes
+varies by component:
+
+-  *Core Metadata:* Send your patches to the
+   :oe_lists:`openembedded-core </g/openembedded-core>`
+   mailing list. For example, a change to anything under the ``meta`` or
+   ``scripts`` directories should be sent to this mailing list.
+
+-  *BitBake:* For changes to BitBake (i.e. anything under the
+   ``bitbake`` directory), send your patches to the
+   :oe_lists:`bitbake-devel </g/bitbake-devel>`
+   mailing list.
+
+-  *"meta-\*" trees:* These trees contain Metadata. Use the
+   :yocto_lists:`poky </g/poky>` mailing list.
+
+-  *Documentation*: For changes to the Yocto Project documentation, use the
+   :yocto_lists:`docs </g/docs>` mailing list.
+
+For changes to other layers and tools hosted in the Yocto Project source
+repositories (i.e. :yocto_git:`git.yoctoproject.org <>`), use the
+:yocto_lists:`yocto </g/yocto/>` general mailing list.
+
+For changes to other layers hosted in the OpenEmbedded source
+repositories (i.e. :oe_git:`git.openembedded.org <>`), use
+the :oe_lists:`openembedded-devel </g/openembedded-devel>`
+mailing list, unless specified otherwise in the layer's ``README`` file.
+
+If you intend to submit a new recipe that neither fits into the core Metadata,
+nor into :oe_git:`meta-openembedded </meta-openembedded/>`, you should
+look for a suitable layer in https://layers.openembedded.org. If similar
+recipes can be expected, you may consider :ref:`dev-manual/layers:creating your own layer`.
+
+If in doubt, please ask on the :yocto_lists:`yocto </g/yocto/>` general mailing list
+or on the :oe_lists:`openembedded-devel </g/openembedded-devel>` mailing list.
+
+Subscribing to the Mailing List
+-------------------------------
+
+After identifying the right mailing list to use, you will have to subscribe to
+it if you haven't done it yet.
+
+If you attempt to send patches to a list you haven't subscribed to, your email
+will be returned as undelivered.
+
+However, if you don't want to be receive all the messages sent to a mailing list,
+you can set your subscription to "no email". You will still be a subscriber able
+to send messages, but you won't receive any e-mail. If people reply to your message,
+their e-mail clients will default to including your email address in the
+conversation anyway.
+
+Anyway, you'll also be able to access the new messages on mailing list archives,
+either through a web browser, or for the lists archived on https://lore.kernelorg,
+through an individual newsgroup feed or a git repository.
+
+Sending Patches via Email
+-------------------------
+
+At this stage, you are ready to send your patches via email. Here's the
+typical usage of ``git send-email``::
+
+   git send-email --to <mailing-list-address> *.patch
+
+Then, review each subject line and list of recipients carefully, and then
+and then allow the command to send each message.
+
+You will see that ``git send-email`` will automatically copy the people listed
+in any commit tags such as ``Signed-off-by`` or ``Reported-by``.
+
+In case you are sending patches for :oe_git:`meta-openembedded </meta-openembedded/>`
+or any layer other than :oe_git:`openembedded-core </openembedded-core/>`,
+please add the appropriate prefix so that it is clear which layer the patch is intended
+to be applied to::
+
+   git send-email --subject-prefix="meta-oe][PATCH" ...
+
+.. note::
+
+   It is actually possible to send patches without generating them
+   first. However, make sure you have reviewed your changes carefully
+   because ``git send-email`` will just show you the title lines of
+   each patch.
+
+   Here's a command you can use if you just have one patch in your
+   branch::
+
+      git send-email --to <mailing-list-address> -1
+
+   If you have multiple patches and a cover letter, you can send
+   patches for all the commits between the reference branch
+   and the tip of your branch::
+
+      git send-email --cover-letter --cover-from-description=auto --to <mailing-list-address> -M <ref-branch>
+
+See the `git send-email manual page <https://git-scm.com/docs/git-send-email>`__
+for details.
+
+Troubleshooting Email Issues
+----------------------------
+
+Fixing your From identity
+~~~~~~~~~~~~~~~~~~~~~~~~~
+
+We have a frequent issue with contributors whose patches are received through
+a ``From`` field which doesn't match the ``Signed-off-by`` information. Here is
+a typical example for people sending from a domain name with :wikipedia:`DMARC`::
+
+   From: "Linus Torvalds via lists.openembedded.org <linus.torvalds=kernel.org@lists.openembedded.org>"
+
+This ``From`` field is used by ``git am`` to recreate commits with the right
+author name. The following will ensure that your e-mails have an additional
+``From`` field at the beginning of the Email body, and therefore that
+maintainers accepting your patches don't have to fix commit author information
+manually::
+
+   git config --global sendemail.from "linus.torvalds@kernel.org"
+
+The ``sendemail.from`` should match your ``user.email`` setting,
+which appears in the ``Signed-off-by`` line of your commits.
+
+Streamlining git send-email usage
+---------------------------------
+
+If you want to save time and not be forced to remember the right options to use
+with ``git send-email``, you can use Git configuration settings.
+
+-  To set the right mailing list address for a given repository::
+
+      git config --local sendemail.to openembedded-devel@lists.openembedded.org
+
+-  If the mailing list requires a subject prefix for the layer
+   (this only works when the repository only contains one layer)::
+
+      git config --local format.subjectprefix "meta-something][PATCH"
+
+Using Scripts to Push a Change Upstream and Request a Pull
+==========================================================
+
+For larger patch series it is preferable to send a pull request which not
+only includes the patch but also a pointer to a branch that can be pulled
+from. This involves making a local branch for your changes, pushing this
+branch to an accessible repository and then using the ``create-pull-request``
+and ``send-pull-request`` scripts from openembedded-core to create and send a
+patch series with a link to the branch for review.
+
+Follow this procedure to push a change to an upstream "contrib" Git
+repository once the steps in
+":ref:`contributor-guide/submit-changes:preparing changes for submission`"
+have been followed:
+
+.. note::
+
+   You can find general Git information on how to push a change upstream
+   in the
+   `Git Community Book <https://git-scm.com/book/en/v2/Distributed-Git-Distributed-Workflows>`__.
+
+#. *Request Push Access to an "Upstream" Contrib Repository:* Send an email to
+   ``helpdesk@yoctoproject.org``:
+
+    -  Attach your SSH public key which usually named ``id_rsa.pub.``.
+       If you don't have one generate it by running ``ssh-keygen -t rsa -b 4096 -C "your_email@example.com"``.
+
+    -  List the repositories you're planning to contribute to.
+
+    -  Include your preferred branch prefix for ``-contrib`` repositories.
+
+#. *Push Your Commits to the "Contrib" Upstream:* Push your
+   changes to that repository::
+
+      $ git push upstream_remote_repo local_branch_name
+
+   For example, suppose you have permissions to push
+   into the upstream ``meta-intel-contrib`` repository and you are
+   working in a local branch named `your_name`\ ``/README``. The following
+   command pushes your local commits to the ``meta-intel-contrib``
+   upstream repository and puts the commit in a branch named
+   `your_name`\ ``/README``::
+
+      $ git push meta-intel-contrib your_name/README
+
+#. *Determine Who to Notify:* Determine the maintainer or the mailing
+   list that you need to notify for the change.
+
+   Before submitting any change, you need to be sure who the maintainer
+   is or what mailing list that you need to notify. Use either these
+   methods to find out:
+
+   -  *Maintenance File:* Examine the ``maintainers.inc`` file, which is
+      located in the :term:`Source Directory` at
+      ``meta/conf/distro/include``, to see who is responsible for code.
+
+   -  *Search by File:* Using :ref:`overview-manual/development-environment:git`, you can
+      enter the following command to bring up a short list of all
+      commits against a specific file::
+
+         git shortlog -- filename
+
+      Just provide the name of the file for which you are interested. The
+      information returned is not ordered by history but does include a
+      list of everyone who has committed grouped by name. From the list,
+      you can see who is responsible for the bulk of the changes against
+      the file.
+
+   -  *Find the Mailing List to Use:* See the
+      ":ref:`contributor-guide/submit-changes:finding a suitable mailing list`"
+      section above.
+
+#. *Make a Pull Request:* Notify the maintainer or the mailing list that
+   you have pushed a change by making a pull request.
+
+   The Yocto Project provides two scripts that conveniently let you
+   generate and send pull requests to the Yocto Project. These scripts
+   are ``create-pull-request`` and ``send-pull-request``. You can find
+   these scripts in the ``scripts`` directory within the
+   :term:`Source Directory` (e.g.
+   ``poky/scripts``).
+
+   Using these scripts correctly formats the requests without
+   introducing any whitespace or HTML formatting. The maintainer that
+   receives your patches either directly or through the mailing list
+   needs to be able to save and apply them directly from your emails.
+   Using these scripts is the preferred method for sending patches.
+
+   First, create the pull request. For example, the following command
+   runs the script, specifies the upstream repository in the contrib
+   directory into which you pushed the change, and provides a subject
+   line in the created patch files::
+
+      $ poky/scripts/create-pull-request -u meta-intel-contrib -s "Updated Manual Section Reference in README"
+
+   Running this script forms ``*.patch`` files in a folder named
+   ``pull-``\ `PID` in the current directory. One of the patch files is a
+   cover letter.
+
+   Before running the ``send-pull-request`` script, you must edit the
+   cover letter patch to insert information about your change. After
+   editing the cover letter, send the pull request. For example, the
+   following command runs the script and specifies the patch directory
+   and email address. In this example, the email address is a mailing
+   list::
+
+      $ poky/scripts/send-pull-request -p ~/meta-intel/pull-10565 -t meta-intel@lists.yoctoproject.org
+
+   You need to follow the prompts as the script is interactive.
+
+   .. note::
+
+      For help on using these scripts, simply provide the ``-h``
+      argument as follows::
+
+              $ poky/scripts/create-pull-request -h
+              $ poky/scripts/send-pull-request -h
+
+Submitting Changes to Stable Release Branches
+=============================================
+
+The process for proposing changes to a Yocto Project stable branch differs
+from the steps described above. Changes to a stable branch must address
+identified bugs or CVEs and should be made carefully in order to avoid the
+risk of introducing new bugs or breaking backwards compatibility. Typically
+bug fixes must already be accepted into the master branch before they can be
+backported to a stable branch unless the bug in question does not affect the
+master branch or the fix on the master branch is unsuitable for backporting.
+
+The list of stable branches along with the status and maintainer for each
+branch can be obtained from the
+:yocto_wiki:`Releases wiki page </Releases>`.
+
+.. note::
+
+   Changes will not typically be accepted for branches which are marked as
+   End-Of-Life (EOL).
+
+With this in mind, the steps to submit a change for a stable branch are as
+follows:
+
+#. *Identify the bug or CVE to be fixed:* This information should be
+   collected so that it can be included in your submission.
+
+   See :ref:`dev-manual/vulnerabilities:checking for vulnerabilities`
+   for details about CVE tracking.
+
+#. *Check if the fix is already present in the master branch:* This will
+   result in the most straightforward path into the stable branch for the
+   fix.
+
+   #. *If the fix is present in the master branch --- submit a backport request
+      by email:* You should send an email to the relevant stable branch
+      maintainer and the mailing list with details of the bug or CVE to be
+      fixed, the commit hash on the master branch that fixes the issue and
+      the stable branches which you would like this fix to be backported to.
+
+   #. *If the fix is not present in the master branch --- submit the fix to the
+      master branch first:* This will ensure that the fix passes through the
+      project's usual patch review and test processes before being accepted.
+      It will also ensure that bugs are not left unresolved in the master
+      branch itself. Once the fix is accepted in the master branch a backport
+      request can be submitted as above.
+
+   #. *If the fix is unsuitable for the master branch --- submit a patch
+      directly for the stable branch:* This method should be considered as a
+      last resort. It is typically necessary when the master branch is using
+      a newer version of the software which includes an upstream fix for the
+      issue or when the issue has been fixed on the master branch in a way
+      that introduces backwards incompatible changes. In this case follow the
+      steps in ":ref:`contributor-guide/submit-changes:preparing changes for submission`"
+      and in the following sections but modify the subject header of your patch
+      email to include the name of the stable branch which you are
+      targetting. This can be done using the ``--subject-prefix`` argument to
+      ``git format-patch``, for example to submit a patch to the
+      "&DISTRO_NAME_NO_CAP_MINUS_ONE;" branch use::
+
+         git format-patch --subject-prefix='&DISTRO_NAME_NO_CAP_MINUS_ONE;][PATCH' ...
+
+Taking Patch Review into Account
+================================
+
+You may get feedback on your submitted patches from other community members
+or from the automated patchtest service. If issues are identified in your
+patches then it is usually necessary to address these before the patches are
+accepted into the project. In this case you should your commits according
+to the feedback and submit an updated version to the relevant mailing list.
+
+In any case, never fix reported issues by fixing them in new commits
+on the tip of your branch. Always come up with a new series of commits
+without the reported issues.
+
+.. note::
+
+   It is a good idea to send a copy to the reviewers who provided feedback
+   to the previous version of the patch. You can make sure this happens
+   by adding a ``CC`` tag to the commit description::
+
+      CC: William Shakespeare <bill@yoctoproject.org>
+
+A single patch can be amended using ``git commit --amend``, and multiple
+patches can be easily reworked and reordered through an interactive Git rebase::
+
+   git rebase -i <ref-branch>
+
+See `this tutorial <https://hackernoon.com/beginners-guide-to-interactive-rebasing-346a3f9c3a6d>`__
+for practical guidance about using Git interactive rebasing.
+
+You should also modify the ``[PATCH]`` tag in the email subject line when
+sending the revised patch to mark the new iteration as ``[PATCH v2]``,
+``[PATCH v3]``, etc as appropriate. This can be done by passing the ``-v``
+argument to ``git format-patch`` with a version number::
+
+   git format-patch -v2 <ref-branch>
+
+Lastly please ensure that you also test your revised changes. In particular
+please don't just edit the patch file written out by ``git format-patch`` and
+resend it.
+
+Tracking the Status of Patches
+==============================
+
+The Yocto Project uses a `Patchwork instance <https://patchwork.yoctoproject.org/>`__
+to track the status of patches submitted to the various mailing lists and to
+support automated patch testing. Each submitted patch is checked for common
+mistakes and deviations from the expected patch format and submitters are
+notified by ``patchtest`` if such mistakes are found. This process helps to
+reduce the burden of patch review on maintainers.
+
+.. note::
+
+   This system is imperfect and changes can sometimes get lost in the flow.
+   Asking about the status of a patch or change is reasonable if the change
+   has been idle for a while with no feedback.
+
+If your patches have not had any feedback in a few days, they may have already
+been merged. You can run ``git pull``  branch to check this. Note that many if
+not most layer maintainers do not send out acknowledgement emails when they
+accept patches. Alternatively, if there is no response or merge after a few days
+the patch may have been missed or the appropriate reviewers may not currently be
+around. It is then perfectly fine to reply to it yourself with a reminder asking
+for feedback.
+
+.. note::
+
+      Patch reviews for feature and recipe upgrade patches are likely be delayed
+      during a feature freeze because these types of patches aren't merged during
+      at that time --- you may have to wait until after the freeze is lifted.
+
+Maintainers also commonly use ``-next`` branches to test submissions prior to
+merging patches. Thus, you can get an idea of the status of a patch based on
+whether the patch has been merged into one of these branches. The commonly
+used testing branches for OpenEmbedded-Core are as follows:
+
+-  *openembedded-core "master-next" branch:* This branch is part of the
+   :oe_git:`openembedded-core </openembedded-core/>` repository and contains
+   proposed changes to the core metadata.
+
+-  *poky "master-next" branch:* This branch is part of the
+   :yocto_git:`poky </poky/>` repository and combines proposed
+   changes to BitBake, the core metadata and the poky distro.
+
+Similarly, stable branches maintained by the project may have corresponding
+``-next`` branches which collect proposed changes. For example,
+``&DISTRO_NAME_NO_CAP;-next`` and ``&DISTRO_NAME_NO_CAP_MINUS_ONE;-next``
+branches in both the "openembdedded-core" and "poky" repositories.
+
+Other layers may have similar testing branches but there is no formal
+requirement or standard for these so please check the documentation for the
+layers you are contributing to.
+