Submitting Patches — The Mesa 3D Graphics Library latest documentation (original) (raw)

Introduction

Mesa contribution is a collaborative process that works like this: A contributor proposes a change (usually in the form of a GitLab merge request), which must undergo a review (usually in the form of comments from the maintainers on the merge request).

The maintainers either accept it as-is, reject it outright, or request changes from the contributor before a contribution can be accepted.

Mesa is a project that is made up of many different subprojects, for example drivers, API frontends, shader compiler infrastructure, etc. Each of these parts may have different maintainers and/or different rules and conventions. It is up to the maintainers of each specific part to decide what is acceptable for them and to direct the development of that part.

Expectations on contributors

Due to the collaborative nature of development, the expectation is that the contributor engages with the maintainers and works with us to shape the changeset into a form that can be accepted in the project.

If you want to contribute code to Mesa, we highly recommend the following:

In case you are not familiar with the code base, it’s okay to ask for help and guidance from more experienced developers.

The submitter is responsible for the code change, regardless of where that code change came from, whether they wrote it themselves, used an “AI” or other tool, or got it from someone else. That responsibility includes making sure that the code change can be submitted under the MIT license that Mesa uses.

The submitter needs to understand what code they are changing, what the change does, and justify that change in the commit messages. Using coding assistants or “AI” or other tools does not grant additional privileges or reduce our expectations.

If you don’t know programming (and don’t want to learn), but you are interested in the Mesa project, there are plenty of other ways to contribute besides writing code, for example reporting bugs, benchmarking, testing changes, etc.

Basic guidelines

Patch formatting

The Fixes: tag

If a patch addresses a issue introduced with earlier commit, that should be noted in the commit message. For example:

Fixes: d7b3707c612 ("util/disk_cache: use stat() to check if entry is a directory")

You can produce those fixes lines by running this command once:

git config --global alias.fixes "show -s --pretty='format:Fixes: %h ("%s")'"

After that, using git fixes <sha1> will print the full line for you.

The stable tag

If you want a commit to be applied to a stable branch, you should add an appropriate note to the commit message.

Using a Fixes: tag as described in Patch formattingis the preferred way to nominate a commit that should be backported. There are scripts that will figure out which releases to apply the patch to automatically, so you don’t need to figure it out.

Alternatively, you may use the Backport-to: tag, as presented in the following example:

This will backport the commit to the 21.0 branch, as well as any more recent stable branch. Multiple Backport-to: lines are allowed, but only the lowest number mentioned actually matters, so for clarity, please only use one.

The last option is deprecated and mostly here for historical reasons dating back to when patch submission was done via emails: using a Cc:tag. Support for this tag will be removed at some point. Here are some examples of such a note:

Cc: mesa-stable Cc: 20.0 CC: 20.0 19.3

Using the CC tag should include the stable branches you want to nominate the patch to. If you do not provide any version it is nominated to all active stable branches.

Testing Patches

It should go without saying that patches must be tested. In general, do whatever testing is prudent.

You should always run the Mesa test suite before submitting patches. The test suite can be run using the ‘meson test’ command. All tests must pass before patches will be accepted, this may mean you have to update the tests themselves.

Whenever possible and applicable, test the patch withPiglit and/ordEQP to check for regressions.

As mentioned at the beginning, patches should be bisectable. A good way to test this is to make use of the `git rebase` command, to run your tests on each commit. Assuming your branch is based offorigin/main, you can run:

$ git rebase --interactive --exec "meson test -C build/" origin/main

replacing "meson test" with whatever other test you want to run.

Submitting Patches

Patches are submitted to the Mesa project via aGitLab Merge Request (MR).

When opening a merge request, we recommend the following best practices:

Add a prefix to the title of the MR to indicate which part of the codebase is affected. This is helpful to people who receive many MRs and filter them by title. All commits must also have a prefix. If you are unsure what is the correct prefix, please check the git history for the files you are changing and choose based on that.

If you are already in the ‘developer’ role, add labels to your MR to help reviewers find your MR. For example:

If you don’t add any labels, a bot will attempt to add the correct ones.

Tick the following when creating the MR. It allows developers to rebase your work on top of main.

Allow commits from members who can merge to the target branch

If you revise your patches based on code review and push an update to your branch, you should maintain a clean history in your patches. There should not be “fixup” patches in the history. The series should be buildable and functional after every commit whenever you push the branch.

It is your responsibility to keep the MR alive and making progress, as there are no guarantees that a Mesa dev will independently take interest in it.

Some other notes:

Reviewing Patches

To participate in code review, you can monitor the GitLab Mesa Merge Requestspage, and/or register for notifications in your GitLab settings.

When you’ve reviewed a patch, please be unambiguous about your review. That is, state either

Reviewed-by: Joe Hacker jhacker@foo.com

or

Acked-by: Joe Hacker jhacker@foo.com

Rather than saying just “LGTM” or “Seems OK”.

If small changes are suggested, it’s OK to say something like:

With the above fixes, Reviewed-by: Joe Hacker jhacker@foo.com

which tells the patch author that the patch can be committed, as long as the issues are resolved first.

These Reviewed-by, Acked-by, and Tested-by tags should also be amended into commits in a MR before it is merged.

When providing a Reviewed-by, Acked-by, or Tested-by tag in a GitLab MR, enclose the tag in backticks:

Reviewed-by: Joe Hacker <jhacker@example.com>

This is the markdown format for literal, and will prevent GitLab from hiding the < and > symbols.

Review by non-experts is encouraged. Understanding how someone else goes about solving a problem is a great way to learn your way around the project. The submitter is expected to evaluate whether they have an appropriate amount of review feedback from people who also understand the code before merging their patches.

Merging merge requests

Once a merge request has been appropriately reviewed, its author can decide to merge it.

Warning

Pushing (git push) directly to main is forbidden. This bypasses all the CI checks and is likely to cause issues for everyone else.

Warning

Do not use the “Merge”/”Merge when pipeline succeeds”/”Set to auto-merge” buttons.

We use a custom script to manage this, triggered by assigning the MR to the pseudo-user @marge-bot.

Authors who do not have Developer access (or above) should ask on the merge request for someone else to do it for them, or reach onother channels if the MR reviewers don’t have access themselves.

Do not merge someone else’s MR unless you are sure they don’t have a new version that they are testing locally for instance.When in doubt, ask, for instance by leaving a comment on that MR.

Nominating a commit for a stable branch

There are several ways to nominate a patch for inclusion in the stable branch and release. In order or preference:

Please DO NOT send patches to mesa-stable@lists.freedesktop.org, it is not monitored actively and is a historical artifact.

If you are not the author of the original patch, please Cc: them in your nomination request.

The current patch status can be observed in the staging branch.

Criteria for accepting patches to the stable branch

Mesa has a designated release manager for each stable branch, and the release manager is the only developer that should be pushing changes to these branches. Everyone else should nominate patches using the mechanism described above. The following rules define which patches are accepted and which are not. The stable-release manager is also given broad discretion in rejecting patches that have been nominated.

If the patch complies with the rules it will becherry-picked. Alternatively the release manager will reply to the patch in question stating why the patch has been rejected or would request a backport. The stable-release manager may at times need to force-push changes to the stable branches, for example, to drop a previously-picked patch that was later identified as causing a regression). These force-pushes may cause changes to be lost from the stable branch if developers push things directly. Consider yourself warned.

Sending backports for the stable branch

By default merge conflicts are resolved by the stable-release manager. The release maintainer should resolve trivial conflicts, but for complex conflicts they should ask the original author to provide a backport or denominate the patch.

For patches that either need to be nominated after they’ve landed in main, or that are known ahead of time to not not apply cleanly to a stable branch (such as due to a rename), using a GitLab MR is most appropriate. The MR must be based on and target the YY.N branch, and the release manager will change the target to the staging/YY.N branch when merging it; this avoid issues with the rebasing nature of the stagingbranches. Assigning the MR to release maintainer for said branch or mentioning them is not required but helpful, to allow them to see the MR as soon as possible.

Warning

Do not merge your backport MR yourself, even if you think it’s ready. The release manager will do it once everything is ok.

Make sure to use git cherry-pick -x when cherry-picking the commits from the main branch. This adds the “cherry picked from commit …” line to the commit message, to allow the release maintainters to mark those as backported, which in turn allows the tools to correctly report any future Fixes: affecting the commits you backported.

Documentation patches

Our documentation is written as reStructuredText files in thedocs folder, and built using Sphinx.

Install dependencies (adapt for your distribution)

apk add coreutils graphviz clang-dev musl-dev linux-headers python3 -m venv docs-build ./docs-build/bin/pip3 install sphinx===8.2.3 mako===1.2.3 hawkmoth===0.19.0 clang===$(llvm-config --version)

Build docs (on Debian, set LD_LIBRARY_PATH to /usr/lib/llvm-VERSION/lib so it can find libclang.so)

./docs-build/bin/sphinx-build -W -b html docs docs-html/

The preferred language of the documentation is US English. This doesn’t mean that everyone is expected to pay close attention to the different English variants, but it does mean someone might suggest a spelling-change, either during review or as a follow-up merge-request.

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