5. Contributor’s Guide¶

5.1. Getting Started¶

Make sure you have a Github account and you are logged on developer.trustedfirmware.org.
Create an issue for your work if one does not already exist. This gives everyone visibility of whether others are working on something similar.
- If you intend to include Third Party IP in your contribution, please raise a separate issue for this and ensure that the changes that include Third Party IP are made on a separate topic branch.
Clone Trusted Firmware-A on your own machine as described in Getting the TF-A Source.
Create a local topic branch based on the Trusted Firmware-A master branch.

5.2. Making Changes¶

Make commits of logical units. See these general Git guidelines for contributing to a project.
Follow the Coding Style and 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 create a separate issue and 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 Porting Guide, Firmware Design document or other in-source documentation needs updating.
- 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 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 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.
- If you are submitting new files that you intend to be the technical sub-maintainer for (for example, a new platform port), then also update the Maintainers 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.
Please test your changes. As a minimum, ensure that Linux boots on the Foundation FVP. See Arm Fixed Virtual Platforms (FVP) for more information. For more extensive testing, consider running the TF-A Tests against your patches.

5.3. 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 Developer Certificate of Origin.

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 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 Maintainers. Any review comments will be made directly on your patch. This may require you to do some rework.
Refer to the Gerrit Uploading Changes documentation for more details.
When the changes are accepted, the Maintainers will integrate them.
- Typically, the 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 Maintainers may rebase it on the master 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 merge commit will be removed from the integration branch and the Maintainers will ask you to create a new patch set to resolve the problem.

5.4. 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 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.