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105bccb3b9
For quite a long time we've been using a 3 week, rather than 2 week, merge window as it was only 2 weeks during the timeframe where we did 2 month rather than 3 month releases. This corrects the places that still had 2 weeks and tries to make things a bit clearer overall. Cc: Heinrich Schuchardt <xypron.glpk@gmx.de> Signed-off-by: Tom Rini <trini@konsulko.com>
199 lines
8.0 KiB
ReStructuredText
199 lines
8.0 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0+:
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U-Boot Development Process
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==========================
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Management Summary
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------------------
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* Development happens in Release Cycles of 3 months.
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* The first 3 weeks of the cycle are referred to as the Merge Window, which is
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followed by a Stabilization Period.
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* Patches with new code get only accepted while the Merge Window is open.
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* A patch that is generally in good shape and that was submitted while the
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Merge Window was open is eligible to go into the upcoming release, even if
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changes and resubmits are needed.
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* During the Stabilization Period, only patches that contain bug fixes get
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applied.
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Phases of the Development Process
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---------------------------------
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U-Boot development takes place in `Release Cycles
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<https://www.denx.de/wiki/U-Boot/ReleaseCycle>`_. A Release Cycle lasts
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normally for three months.
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The first three weeks of each Release Cycle are called *Merge Window*.
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It is followed by a *Stabilization Period*.
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The end of a Release Cycle is marked by the release of a new U-Boot version.
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Merge Window
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------------
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The Merge Window is the period when new patches get submitted (and hopefully
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accepted) for inclusion into U-Boot mainline. This period lasts for 21 days (3
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weeks) and ends with the release of ``"-rc1"``.
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This is the only time when new code (like support for new processors or new
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boards, or other new features or reorganization of code) is accepted.
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Twilight Time
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-------------
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Usually patches do not get accepted as they are - the peer review that takes
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place will usually require changes and resubmissions of the patches before they
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are considered to be ripe for inclusion into mainline.
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Also the review often happens not immediately after a patch was submitted,
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but only when somebody (usually the responsible custodian) finds time to do
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this.
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The result is that the final version of such patches gets submitted after the
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merge window has been closed.
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It is current practice in U-Boot that such patches are eligible to go into the
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upcoming release.
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The result is that the release of the ``"-rc1"`` version and formal closing of
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the Merge Window does not preclude patches that were already posted from being
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merged for the upcoming release.
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Stabilization Period
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--------------------
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During the Stabilization Period only patches containing bug fixes get
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applied.
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Corner Cases
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------------
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Sometimes it is not clear if a patch contains a bug fix or not.
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For example, changes that remove dead code, unused macros etc. or
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that contain Coding Style fixes are not strict bug fixes.
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In such situations it is up to the responsible custodian to decide if they
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apply such patches even when the Merge Window is closed.
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Exception: at the end of the Stabilization Period only strict bug
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fixes my be applied.
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Sometimes patches miss the Merge Window slightly - say by a few
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hours or even a day. Patch acceptance is not as critical as a
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financial transaction, or such. So if there is such a slight delay,
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the custodian is free to turn a blind eye and accept it anyway. The
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idea of the development process is to make it foreseeable,
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but not to slow down development.
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It makes more sense if an engineer spends another day on testing and
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cleanup and submits the patch a couple of hours late, instead of
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submitting a green patch which will waste efforts from several people
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during several rounds of review and reposts.
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Differences to the Linux Development Process
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--------------------------------------------
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* In Linux, top-level maintainers will collect patches in their trees and send
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pull requests to Linus as soon as the merge window opens.
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So far, most U-Boot custodians do not work like that; they send pull requests
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only at (or even after) the end of the merge window.
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* In Linux, the closing of the merge window is marked by the release of the
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next ``"-rc1"``
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In U-Boot, ``"-rc1"`` will only be released after all (or at least most of
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the) patches that were submitted during the merge window have been applied.
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Custodians
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----------
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The Custodians take responsibility for some area of the U-Boot code. The
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in-tree ``MAINTAINERS`` files list who is responsible for which areas.
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It is their responsibility to pick up patches from the mailing list
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that fall into their responsibility, and to process these.
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A very important responsibility of each custodian is to provide
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feedback to the submitter of a patch about what is going on: if the
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patch was accepted, or if it was rejected (which exact list of
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reasons), if it needs to be reworked (with respective review
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comments). Even a "I have no time now, will look into it later"
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message is better than nothing. Also, if there are remarks to a
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patch, these should leave no doubt if they were just comments and the
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patch will be accepted anyway, or if the patch should be
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reworked/resubmitted, or if it was rejected.
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Work flow of a Custodian
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------------------------
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The normal flow of work in the U-Boot development process will look
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like this:
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#. A developer submits a patch via e-mail to the u-boot mailing list. In
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U-Boot, we make use of the `Developer Certificate of Origin
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<https://developercertificate.org/>`_ that is common in other projects such
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as the Linux kernel. Following this and adding a ``Signed-off-by:`` line
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that contains the developer's name and email address is required.
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#. Everybody who can is invited to review and test the changes. Typically, we
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follow the same guidelines as the Linux kernel for `Acked-by
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<https://www.kernel.org/doc/html/latest/process/submitting-patches.html#when-to-use-acked-by-cc-and-co-developed-by>`_
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as well as `Reviewed-by
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<https://www.kernel.org/doc/html/latest/process/submitting-patches.html#using-reported-by-tested-by-reviewed-by-suggested-by-and-fixes>`_
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and similar additional tags.
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#. The responsible custodian inspects this patch, especially for:
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#. :doc:`codingstyle`
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#. Basic logic:
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* The patch fixes a real problem.
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* The patch does not introduce new problems, especially it does not break
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other boards or architectures
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#. U-Boot Philosophy, as documented in :doc:`designprinciples`.
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#. Applies cleanly to the source tree. The custodian is expected to put in
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a "best effort" if a patch does not apply cleanly, but can be made to apply
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still. It is up to the custodian to decide how recent of a commit the
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patch must be against. It is acceptable to request patches against the
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last officially released version of U-Boot or newer. Of course a
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custodian can also accept patches against older code. It can be
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difficult to find the correct balance between putting too much work on
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the custodian or too much work on an individual submitting a patch when
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something does not apply cleanly.
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#. Passes :doc:`ci_testing` as this checks for new warnings and other issues.
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#. Note that in some cases more than one custodian may feel responsible for a
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particular change. To avoid duplicated efforts, the custodian who starts
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processing the patch should follow up to the email saying they intend to
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pick it up.
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#. Commits must show original author in the ``author`` field and include all of
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the ``Signed-off-by``, ``Reviewed-by``, etc, tags that have been submitted.
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#. The final decision to accept or reject a patch comes down to the custodian
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in question.
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#. If accepted, the custodian adds the patch to their public git repository.
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Ideally, they will also follow up on the mailing list with some notification
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that it has been applied. This is not always easy given different custodian
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workflows and environments however.
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#. Although a custodian is supposed to perform their own tests it is a
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well-known and accepted fact that they needs help from other developers who
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- for example - have access to the required hardware or other relevant
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environments. Custodians are expected to ask for assistance with testing
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when required.
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#. Custodians are expected to submit a timely pull request of their git
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repository to the main repository. It is strongly encouraged that a CI run
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has been completed prior to submission, but not required.
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