Contributing to ARM Trusted Firmware

Before you start contributing to this project you must sign the ARM Contributor License Agreement (CLA).

Individuals who want to contribute their own work must sign and return an Individual CLA. Companies that want to contribute must sign and return a Corporate CLA if their employees' intellectual property has been assigned to the employer. Copies of the CLAs are available from the contributing page of the ARM website.

For this project, ARM also requires the GitHub account name(s) associated with each individual contributor or the designated employees of corporate contributors. Only contributions originating from these accounts will be considered covered by the CLA. To avoid delay, you should provide the Github account name(s) at the same time as the signed CLA.

ARM reserves the right to not accept a contribution. This may be for technical, commercial or legal reasons.

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.
- If this is your first contribution, you may add your name or your company name to the Acknowledgements 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 we have your signed CLA.
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. 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, ARM will integrate them.
- Typically, ARM 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, ARM may rebase it onto the master branch first, or ask you to do this.
- If the pull request cannot be automatically merged, ARM will ask you to rebase it onto the master branch.
- After final integration testing, ARM will push your merge commit to the master branch. If a problem is found at this stage, the merge commit will be removed from the integration branch and ARM 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.