coreboot Gerrit Etiquette and Guidelines

The following rules are the requirements for behavior in the coreboot codebase in gerrit. These have mainly been unwritten rules up to this point, and should be familiar to most users who have been active in coreboot for a period of time. Following these rules will help reduce friction in the community.

Note that as with many rules, there are exceptions. Some have been noted in the ‘More Detail’ section. If you feel there is an exception not listed here, please discuss it in the mailing list to get this document updated. Don’t just assume that it’s okay, even if someone on IRC says it is.

Summary

These are the expectations for committing, reviewing, and submitting code into coreboot git and gerrit. While breaking individual rules may not have immediate consequences, the coreboot leadership may act on repeated or flagrant violations with or without notice.

  • Don’t violate the licenses.

  • Let non-trivial patches sit in a review state for at least 24 hours before submission.

  • Try to coordinate with platform maintainers when making changes to platforms.

  • If you give a patch a -2, you are responsible for giving concrete recommendations for what could be changed to resolve the issue the patch addresses.

  • Don’t modify other people’s patches without their consent.

  • Be respectful to others when commenting.

  • Don’t submit patches that you know will break other platforms.

More detail

  • Don’t violate the licenses. If you’re submitting code that you didn’t write yourself, make sure the license is compatible with the license of the project you’re submitting the changes to. If you’re submitting code that you wrote that might be owned by your employer, make sure that your employer is aware and you are authorized to submit the code. For clarification, see the Developer’s Certificate of Origin in the coreboot Signed-off-by policy.

  • In general, patches should remain open for review for at least 24 hours since the last significant modification to the change. The purpose is to let coreboot developers around the world have a chance to review. Complex reworks, even if they don’t change the purpose of the patch but the way it’s implemented, should restart the wait period.

  • A change can go in without the wait period if its purpose is to fix a recently-introduced issue (build, boot or OS-level compatibility, not necessarily identified by coreboot.org facilities). Its commit message has to explain what change introduced the problem and the nature of the problem so that the emergency need becomes apparent. Avoid stating something like “fix build error” in the commit summary, describe what the commit does instead, just like any other commit. In addition, it is recommended to reference the commit that introduced the issue. The change itself should be as limited in scope and impact as possible to make it simple to assess the impact. Such a change can be merged early with 3 Code-Review+2. For emergency fixes that affect a single project (SoC, mainboard, …) it’s strongly recommended to get a review by somebody not involved with that project to ensure that the documentation of the issue is clear enough.

  • Trivial changes that deal with minor issues like inconsistencies in whitespace or spelling fixes that don’t impact the final binary output also don’t need to wait. Such changes should point out in their commit messages how the the author verified that the binary output is identical (e.g. a TIMELESS build for a given configuration). When submitting such changes early, the submitter must be different from the author and must document the intent in the Gerrit discussion, e.g. “landed the change early because it’s trivial”. Note that trivial fixes shouldn’t necessarily be expedited: Just like they’re not critical enough for things to go wrong because of them, they’re not critical enough to require quick handling. This exception merely serves to acknowledge that a round-the-world review just isn’t necessary for some types of changes.

  • As explained in our Code of Conduct, we try to assume the best of each other in this community. It’s okay to discuss mistakes (e.g. isolated instances of non-trivial and non-critical changes submitted early) but try to keep such inquiries blameless. If a change leads to problems with our code, the focus should be on fixing the issue, not on assigning blame.

  • Do not +2 patches that you authored or own, even for something as trivial as whitespace fixes. When working on your own patches, it’s easy to overlook something like accidentally updating file permissions or git submodule commit IDs. Let someone else review the patch. An exception to this would be if two people worked in the patch together. If both +2 the patch, that is acceptable, as each is giving a +2 to the other’s work.

  • Try to coordinate with platform maintainers and other significant contributors to the code when making changes to platforms. The platform maintainers are the users who initially pushed the code for that platform, as well as users who have made significant changes to a platform. To find out who maintains a piece of code, please use util/scripts/maintainers.go or refer to the original author of the code in git log.

  • If you give a patch a -2, you are responsible for giving concrete recommendations for what could be changed to resolve the issue the patch addresses. If you feel strongly that a patch should NEVER be merged, you are responsible for defending your position and listening to other points of view. Giving a -2 and walking away is not acceptable, and may cause your -2 to be removed by the coreboot leadership after no less than a week. A notification that the -2 will be removed unless there is a response will be sent out at least 2 days before it is removed.

  • Don’t modify other people’s patches unless you have coordinated this with the owner of that patch. Not only is this considered rude, but your changes could be unintentionally lost. An exception to this would be for patches that have not been updated for more than 90 days. In that case, the patch can be taken over if the original author does not respond to requests for updates. Alternatively, a new patch can be pushed with the original content, and both patches should be updated to reference the other.

  • Be respectful to others when commenting on patches. Comments should be kept to the code, and should be kept in a polite tone. We are a worldwide community and English is a difficult language. Assume your colleagues are intelligent and do not intend disrespect. Resist the urge to retaliate against perceived verbal misconduct, such behavior is not conducive to getting patches merged.

  • Don’t submit code that you know will break other platforms. If your patch affects code that is used by other platforms, it should be compatible with those platforms. While it would be nice to update any other platforms, you must at least provide a path that will allow other platforms to continue working.

Sign-off Procedure

The coreboot project employs a sign-off procedure similar to what is used by the Linux kernel. Each gerrit commit requires a sign-off line saying that the contributed code abides by the Developer’s certificate of origin, below.

Signed-off-by: Random J Developer <random@developer.example.org>

Using ‘-s’ with ‘git commit’ will automatically add a Signed-off-by line to your commit message. Patches without a Signed-off-by should not be pushed to gerrit, and will be rejected by coreboot’s CI system.

You must use a known identity in the Signed-off-by line. Anonymous contributions cannot be committed! This can be anything sufficient to identify and contact the source of a contribution, such as your name or an established alias/nickname. Refer to this LKML thread and the SCO-Linux disputes for the rationale behind the DCO.

Developer’s Certificate of Origin 1.1

By making a contribution to this project, I certify that:

(a) The contribution was created in whole or in part by me and I have the right to submit it under the open source license indicated in the file; or

(b) The contribution is based upon previous work that, to the best of my knowledge, is covered under an appropriate open source license and I have the right under that license to submit that work with modifications, whether created in whole or in part by me, under the same open source license (unless I am permitted to submit under a different license), as indicated in the file; or

(c) The contribution was provided directly to me by some other person who certified (a), (b) or (c) and I have not modified it; and

(d) In the case of each of (a), (b), or (c), I understand and agree that this project and the contribution are public and that a record of the contribution (including all personal information I submit with it, including my sign-off) is maintained indefinitely and may be redistributed consistent with this project or the open source license indicated in the file.

Note: The Developer’s Certificate of Origin 1.1 is licensed under the terms of the Creative Commons Attribution-ShareAlike 2.5 License.

Recommendations for gerrit activity

These guidelines are less strict than the ones listed above. These are more of the “good idea” variety. You are requested to follow the below guidelines, but there will probably be no actual consequences if they’re not followed. That said, following the recommendations below will speed up review of your patches, and make the members of the community do less work.

  • Each patch should be kept to one logical change, which should be described in the title of the patch. Unrelated changes should be split out into separate patches. Fixing whitespace on a line you’re editing is reasonable. Fixing whitespace around the code you’re working on should be a separate ‘cleanup’ patch. Larger patches that touch several areas are fine, so long as they are one logical change. Adding new chips and doing code cleanup over wide areas are two examples of this.

  • Test your patches before submitting them to gerrit. It’s also appreciated if you add a line to the commit message describing how the patch was tested. This prevents people from having to ask whether and how the patch was tested. Examples of this sort of comment would be ‘TEST=Built platform’ or ‘Tested by building and booting platform’. Stating that the patch was not tested is also fine, although you might be asked to do some testing in cases where that would be reasonable.

  • Take advantage of the lint tools to make sure your patches don’t contain trivial mistakes. By running ‘make gitconfig’, the lint-stable tools are automatically put in place and will test your patches before they are committed. As a violation of these tools will cause the jenkins build test to fail, it’s to your advantage to test this before pushing to gerrit.

  • Don’t submit patch trains longer than around 20 patches unless you understand how to manage long patch trains. Long patch trains can become difficult to handle and tie up the build servers for long periods of time if not managed well. Rebasing a patch train over and over as you fix earlier patches in the train can hide comments, and make people review the code multiple times to see if anything has changed between revisions. When pushing long patch trains, it is recommended to only push the full patch train once - the initial time, and only to rebase three or four patches at a time.

  • Run ‘make what-jenkins-does’ locally on patch trains before submitting. This helps verify that the patch train won’t tie up the jenkins builders for no reason if there are failing patches in the train. For running parallel builds, you can specify the number of cores to use by setting the the CPUS environment variable. Example:

make what-jenkins-does CPUS=8

  • Use a topic when pushing a train of patches. This groups the commits together so people can easily see the connection at the top level of gerrit. Topics can be set for individual patches in gerrit by going into the patch and clicking on the icon next to the topic line. Topics can also be set when you push the patches into gerrit. For example, to push a set of commits with the i915-kernel-x60 set, use the command:

git push origin HEAD:refs/for/main%topic=i915-kernel-x60

  • If one of your patches isn’t ready to be merged, make sure it’s obvious that you don’t feel it’s ready for merge yet. The preferred way to show this is by marking in the commit message that it’s not ready until X. The commit message can be updated easily when it’s ready to be pushed. Examples of this are “WIP: title” or “[NEEDS_TEST]: title”. Another way to mark the patch as not ready would be to give it a -1 or -2 review, but isn’t as obvious as the commit message. These patches can also be pushed with the wip flag:

git push origin HEAD:refs/for/main%wip

  • When pushing patches that are not for submission, these should be marked as such. This can be done in the title ‘[DONOTSUBMIT]’, or can be pushed as private changes, so that only explicitly added reviewers will see them. These sorts of patches are frequently posted as ideas or RFCs for the community to look at. Note that private changes can still be fetched from Gerrit by anybody who knows their commit ID, so don’t use this for sensitive changes. To push a private change, use the command:

git push origin HEAD:refs/for/main%private

  • Multiple push options can be combined:

git push origin HEAD:refs/for/main%private,wip,topic=experiment

  • Respond to anyone who has taken the time to review your patches, even if it’s just to say that you disagree. While it may seem annoying to address a request to fix spelling or ‘trivial’ issues, it’s generally easy to handle in gerrit’s built-in editor. If you do use the built-in editor, remember to get that change to your local copy before re-pushing. It’s also acceptable to add fixes for these sorts of comments to another patch, but it’s recommended that that patch be pushed to gerrit before the initial patch gets submitted.

  • Consider breaking up large individual patches into smaller patches grouped by areas. This makes the patches easier to review, but increases the number of patches. The way you want to handle this is a personal decision, as long as each patch is still one logical change.

  • If you have an interest in a particular area or mainboard, set yourself up as a ‘maintainer’ of that area by adding yourself to the MAINTAINERS file in the coreboot root directory. Eventually, this should automatically add you as a reviewer when an area that you’re listed as a maintainer is changed.

  • Submit mainboards that you’re working on to the board-status repo. This helps others and shows that these mainboards are currently being maintained. At some point, boards that are not up to date in the board-status repo will probably end up getting removed from the coreboot main branch.

  • Abandon patches that are no longer useful, or that you don’t intend to keep working on to get submitted.

  • Bring attention to patches that you would like reviewed. Add reviewers, ask for reviewers on IRC or even just rebase it against the current codebase to bring it to the top of the gerrit list. If you’re not sure who would be a good reviewer, look in the MAINTAINERS file or git history of the files that you’ve changed, and add those people.

  • Familiarize yourself with the coreboot commit message guidelines, before pushing patches. This will help to keep annoying requests to fix your commit message to a minimum.

  • If there have been comments or discussion on a patch, verify that the comments have been addressed before giving a +2. If you feel that a comment is invalid, please respond to that comment instead of just ignoring it.

  • Be conscientious when reviewing patches. As a reviewer who approves (+2) a patch, you are responsible for the patch and the effect it has on the codebase. In the event that the patch breaks things, you are expected to be actively involved in the cleanup effort. This means you shouldn’t +2 a patch just because you trust the author of a patch - Make sure you understand what the implications of a patch might be, or leave the review to others. Partial reviews, reviewing code style, for example, can be given a +1 instead of a +2. This also applies if you think the patch looks good, but may not have the experience to know if there may be unintended consequences.

  • If there is still ongoing discussion to a patch, try to wait for a conclusion to the discussion before submitting it to the tree. If you feel that someone is just bikeshedding, maybe just state that and give a time that the patch will be submitted if no new objections are raised.

  • When working with patch trains, for minor requests it’s acceptable to create a fix addressing a comment in another patch at the end of the patch train. This minimizes rebases of the patch train while still addressing the request. For major problems where the change doesn’t work as intended or breaks other platforms, the change really needs to go into the original patch.

  • When bringing in a patch from another git repo, update the original git/gerrit tags by prepending the lines with ‘Original-’. Marking the original text this way makes it much easier to tell what changes happened in which repository. This applies to these lines, not the actual commit message itself:

    • Commit-Id:

    • Change-Id:

    • Signed-off-by:

    • Reviewed-on:

    • Tested-by:

    • Reviewed-by:

The script util/gitconfig/rebase.sh can be used to help automate this. Other tags such as ‘Commit-Queue’ can simply be removed.

  • Check if there’s documentation that needs to be updated to remain current after your change. If there’s no documentation for the part of coreboot you’re working on, consider adding some.

  • When contributing a significant change to core parts of the code base (such as the boot state machine or the resource allocator), or when introducing a new way of doing something that you think is worthwhile to apply across the tree (e.g. board variants), please bring up your design on the mailing list. When changing behavior substantially, an explanation of what changes and why may be useful to have, either in the commit message or, if the discussion of the subject matter needs way more space, in the documentation. Since “what we did in the past and why it isn’t appropriate anymore” isn’t the most useful reading several years down the road, such a description could be put into the release notes for the next version (that you can find in Documentation/releases/) where it will inform people now without cluttering up the regular documentation, and also gives a nice shout-out to your contribution by the next release.

Expectations contributors should have

  • Don’t expect that people will review your patch unless you ask them to. Adding other people as reviewers is the easiest way. Asking for reviews for individual patches in the IRC channel, or by sending a direct request to an individual through your favorite messenger is usually the best way to get a patch reviewed quickly.

  • Don’t expect that your patch will be submitted immediately after getting a +2. As stated previously, non-trivial patches should wait at least 24 hours before being submitted. That said, if you feel that your patch or series of patches has been sitting longer than needed, you can ask for it to be submitted on IRC, or comment that it’s ready for submission in the patch. This will move it to the top of the list where it’s more likely to be noticed and acted upon.

  • Reviews are about the code. It’s easy to take it personally when someone is criticising your code, but the whole idea is to get better code into our codebase. Again, this also applies in the other direction: review code, criticize code, but don’t make it personal.

Gerrit user roles

There are a few relevant roles a user can have on Gerrit:

  • The anonymous user can check out source code.

  • A registered user can also comment and give “+1” code reviews.

  • A reviewer can give “-1” and “+2” code reviews.

  • A core developer can also give “-2” (that is, blocking) code reviews and submit changes.

Anybody can register an account on our instance, using either an OpenID provider or OAuth through GitHub or Google.

The reviewer group is still quite open: Any core developer can add registered users to that group and should do so once some activity (commits, code reviews, and so on) has demonstrated rough knowledge of how we handle things.

A core developer should be sufficiently well established in the community so that they feel comfortable when submitting good patches, when asking for improvements to less good patches and reasonably uncomfortable when -2’ing patches. They’re typically the go-to person for some part of the coreboot tree and ideally listed as its maintainer in our MAINTAINERS registry. To become part of this group, a candidate developer who already demonstrated proficiency with the code base as a reviewer should be nominated, by themselves or others, at the regular coreboot leadership meetings where a decision is made.

Core developers are expected to use their privileges for the good of the project, which includes any of their own coreboot development but also beyond that. They should make sure that ready changes don’t linger around needlessly just because their authors aren’t well-connected with core developers but submit them if they went through review and generally look reasonable. They’re also expected to help clean-up breakage as a result of their submissions.

Since the project expects some activity by core developers, long-term absence (as in “years”) can lead to removal from the group, which can easily be reversed after they come back.

Requests for clarification and suggestions for updates to these guidelines should be sent to the coreboot mailing list at coreboot@coreboot.org.