Contributing to ARM Trusted Firmware

Getting Started

Make sure you have a GitHub account.
Create an issue for your work if one does not already exist. This gives everyone visibility of whether others are working on something similar. ARM licensees may contact ARM directly via their partner managers instead if they prefer.
- Note that the issue tracker for this project is in a separate issue tracking repository. Please follow the guidelines in that repository.
- 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.
Fork arm-trusted-firmware on GitHub.
Clone the fork to your own machine.
Create a local topic branch based on the arm-trusted-firmware master branch.

Making Changes

Make commits of logical units. See these general Git guidelines for contributing to a project.
Follow the Linux coding style; this style is enforced for the ARM Trusted Firmware project (style errors only, not warnings).
- Use the checkpatch.pl script provided with the Linux source tree. A Makefile target is provided for convenience (see section 2 in the User Guide).
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 a GitHub issue, include a reference (e.g. "fixes arm-software/tf-issues#45"); this ensures the issue is automatically closed when merged into the arm-trusted-firmware master branch.
Where appropriate, please update the documentation.
- Consider whether the User Guide, Porting Guide, Firmware Design 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 the copyright notice and BSD-3-Clause SPDX license identifier as shown in license.md. Files that contain changes to imported Third Party IP should contain a notice as follows, with the original copyright and license text retained:
```
Portions copyright (c) [XXXX-]YYYY, ARM Limited and Contributors. All rights reserved.
```
  where XXXX is the year of first contribution (if different to YYYY) and YYYY is the year of most recent contribution.
- If not done previously, you may add your name or your company name to the Acknowledgements file.
- 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 UEFI boots to the shell on the Foundation FVP. See the "Running the software" section of the User Guide for more information.

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 (DCO).
Push your local changes to your fork of the repository.
Submit a pull request to the arm-trusted-firmware integration branch.
- The changes in the pull request will then undergo further review and testing by the Maintainers. Any review comments will be made as comments on the pull request. This may require you to do some rework.
When the changes are accepted, the Maintainers will integrate them.
- Typically, the Maintainers will merge the pull request into the integration branch within the GitHub UI, creating a merge commit.
- Please avoid creating merge commits in the pull request itself.
- If the pull request is not based on a recent commit, the Maintainers may rebase it onto the master branch first, or ask you to do this.
- If the pull request cannot be automatically merged, the Maintainers will ask you to rebase it onto the master branch.
- After final integration testing, the Maintainers will push your merge commit to 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 pull request to resolve the problem.
- Please do not delete your topic branch until it is safely merged into the master branch.