The Mesa 3D Graphics Library

Submitting Patches

Basic guidelines

Patch formatting

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 with Piglit and/or dEQP 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 off origin/master, you can run:

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

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

Submitting Patches

Patches are submitted to the Mesa project via a GitLab Merge Request.

Add labels to your MR to help reviewers find it. For example:

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

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 Requests page, 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.

Nominating a commit for a stable branch

There are three ways to nominate a patch for inclusion in the stable branch and release.

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.

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 formatting is the preferred way to nominate a commit that you know ahead of time 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 a "CC:" tag. Here are some examples of such a note:

CC: 20.0 19.3 <mesa-stable@lists.freedesktop.org>

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.

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 be cherry-picked. Alternatively the release manager will reply to the patch in question stating why the patch has been rejected or would request a backport. A summary of all the picked/rejected patches will be presented in the pre-release announcement. 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 de-nominate the patch.

For patches that either need to be nominated after they've landed in master, 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 should be based on and target the staging/year.quarter branch, not on the year.quarter branch, per the stable branch policy. Assigning the MR to release maintainer for said branch or mentioning them is helpful, but not required.

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