Contributor's Guide
===================

Getting Started
---------------

-  Make sure you have a Github account and you are logged on both
   `developer.trustedfirmware.org`_ and `review.trustedfirmware.org`_.

-  If you plan to contribute a major piece of work, it is usually a good idea to
   start a discussion around it on the mailing list. This gives everyone
   visibility of what is coming up, you might learn that somebody else is
   already working on something similar or the community might be able to
   provide some early input to help shaping the design of the feature.

   If you intend to include Third Party IP in your contribution, please mention
   it explicitly in the email thread and ensure that the changes that include
   Third Party IP are made in a separate patch (or patch series).

-  Clone `Trusted Firmware-A`_ on your own machine as described in
   :ref:`prerequisites_get_source`.

-  Create a local topic branch based on the `Trusted Firmware-A`_ ``master``
   branch.

Making Changes
--------------

-  Make commits of logical units. See these general `Git guidelines`_ for
   contributing to a project.

-  Follow the :ref:`Coding Style` and :ref:`Coding Guidelines`.

   -  Use the checkpatch.pl script provided with the Linux source tree. A
      Makefile target is provided for convenience.

-  Keep the commits on topic. If you need to fix another bug or make another
   enhancement, please address it on a separate topic branch.

-  Avoid long commit series. If you do have a long series, consider whether
   some commits should be squashed together or addressed in a separate topic.

-  Make sure your commit messages are in the proper format. If a commit fixes
   an `issue`_, include a reference.

-  Where appropriate, please update the documentation.

   -  Consider whether the :ref:`Porting Guide`, :ref:`Firmware Design` document
      or other in-source documentation needs updating.

   -  If you are submitting new files that you intend to be the code owner for
      (for example, a new platform port), then also update the
      :ref:`code owners` file.

   -  For topics with multiple commits, you should make all documentation changes
      (and nothing else) in the last commit of the series. Otherwise, include
      the documentation changes within the single commit.

-  Ensure that each changed file has the correct copyright and license
   information. Files that entirely consist of contributions to this project
   should have a copyright notice and BSD-3-Clause SPDX license identifier of
   the form as shown in :ref:`license`. Files that contain changes to imported
   Third Party IP files should retain their original copyright and license
   notices.

   For significant contributions you may add your own copyright notice in the
   following format:

   ::

       Portions copyright (c) [XXXX-]YYYY, <OWNER>. All rights reserved.

   where XXXX is the year of first contribution (if different to YYYY) and YYYY
   is the year of most recent contribution. <OWNER> is your name or your company
   name.

-  Please test your changes. As a minimum, ensure that Linux boots on the
   Foundation FVP. See :ref:`Arm Fixed Virtual Platforms (FVP)` for more
   information. For more extensive testing, consider running the `TF-A Tests`_
   against your patches.

Submitting Changes
------------------

-  Ensure that each commit in the series has at least one ``Signed-off-by:``
   line, using your real name and email address. The names in the
   ``Signed-off-by:`` and ``Author:`` lines must match. If anyone else
   contributes to the commit, they must also add their own ``Signed-off-by:``
   line. By adding this line the contributor certifies the contribution is made
   under the terms of the
   :download:`Developer Certificate of Origin <../../dco.txt>`.

   More details may be found in the `Gerrit Signed-off-by Lines guidelines`_.

-  Ensure that each commit also has a unique ``Change-Id:`` line. If you have
   cloned the repository with the "`Clone with commit-msg hook`" clone method
   (following the :ref:`Prerequisites` document), this should already be the
   case.

   More details may be found in the `Gerrit Change-Ids documentation`_.

-  Submit your changes for review at https://review.trustedfirmware.org
   targeting the ``integration`` branch.

   -  The changes will then undergo further review and testing by the
      :ref:`code owners` and :ref:`maintainers`. Any review comments will be
      made directly on your patch. This may require you to do some rework. For
      controversial changes, the discussion might be moved to the `TF-A mailing
      list`_ to involve more of the community.

   Refer to the `Gerrit Uploading Changes documentation`_ for more details.

-  When the changes are accepted, the :ref:`maintainers` will integrate them.

   -  Typically, the :ref:`maintainers` will merge the changes into the
      ``integration`` branch.
   -  If the changes are not based on a sufficiently-recent commit, or if they
      cannot be automatically rebased, then the :ref:`maintainers` may rebase it
      on the ``integration`` branch or ask you to do so.
   -  After final integration testing, the changes will make their way into the
      ``master`` branch. If a problem is found during integration, the
      :ref:`maintainers` will request your help to solve the issue. They may
      revert your patches and ask you to resubmit a reworked version of them or
      they may ask you to provide a fix-up patch.

Binary Components
-----------------

-  Platforms may depend on binary components submitted to the `Trusted Firmware
   binary repository`_ if they require code that the contributor is unable or
   unwilling to open-source. This should be used as a rare exception.
-  All binary components must follow the contribution guidelines (in particular
   licensing rules) outlined in the `readme.rst <tf-binaries-readme_>`_ file of
   the binary repository.
-  Binary components must be restricted to only the specific functionality that
   cannot be open-sourced and must be linked into a larger open-source platform
   port. The majority of the platform port must still be implemented in open
   source. Platform ports that are merely a thin wrapper around a binary
   component that contains all the actual code will not be accepted.
-  Only platform port code (i.e. in the ``plat/<vendor>`` directory) may rely on
   binary components. Generic code must always be fully open-source.

--------------

*Copyright (c) 2013-2020, Arm Limited and Contributors. All rights reserved.*

.. _developer.trustedfirmware.org: https://developer.trustedfirmware.org
.. _review.trustedfirmware.org: https://review.trustedfirmware.org
.. _issue: https://developer.trustedfirmware.org/project/board/1/
.. _Trusted Firmware-A: https://git.trustedfirmware.org/TF-A/trusted-firmware-a.git
.. _Git guidelines: http://git-scm.com/book/ch5-2.html
.. _Gerrit Uploading Changes documentation: https://review.trustedfirmware.org/Documentation/user-upload.html
.. _Gerrit Signed-off-by Lines guidelines: https://review.trustedfirmware.org/Documentation/user-signedoffby.html
.. _Gerrit Change-Ids documentation: https://review.trustedfirmware.org/Documentation/user-changeid.html
.. _TF-A Tests: https://trustedfirmware-a-tests.readthedocs.io
.. _Trusted Firmware binary repository: https://review.trustedfirmware.org/admin/repos/tf-binaries
.. _tf-binaries-readme: https://git.trustedfirmware.org/tf-binaries.git/tree/readme.rst
.. _TF-A mailing list: https://lists.trustedfirmware.org/mailman/listinfo/tf-a