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diff --git a/Documentation/maintainer/modifying-patches.rst b/Documentation/maintainer/modifying-patches.rst new file mode 100644 index 000000000000..58385d2e8065 --- /dev/null +++ b/Documentation/maintainer/modifying-patches.rst @@ -0,0 +1,50 @@ +.. _modifyingpatches: + +Modifying Patches +================= + +If you are a subsystem or branch maintainer, sometimes you need to slightly +modify patches you receive in order to merge them, because the code is not +exactly the same in your tree and the submitters'. If you stick strictly to +rule (c) of the developers certificate of origin, you should ask the submitter +to rediff, but this is a totally counter-productive waste of time and energy. +Rule (b) allows you to adjust the code, but then it is very impolite to change +one submitters code and make him endorse your bugs. To solve this problem, it +is recommended that you add a line between the last Signed-off-by header and +yours, indicating the nature of your changes. While there is nothing mandatory +about this, it seems like prepending the description with your mail and/or +name, all enclosed in square brackets, is noticeable enough to make it obvious +that you are responsible for last-minute changes. Example:: + + Signed-off-by: Random J Developer <random@developer.example.org> + [lucky@maintainer.example.org: struct foo moved from foo.c to foo.h] + Signed-off-by: Lucky K Maintainer <lucky@maintainer.example.org> + +This practice is particularly helpful if you maintain a stable branch and +want at the same time to credit the author, track changes, merge the fix, +and protect the submitter from complaints. Note that under no circumstances +can you change the author's identity (the From header), as it is the one +which appears in the changelog. + +Special note to back-porters: It seems to be a common and useful practice +to insert an indication of the origin of a patch at the top of the commit +message (just after the subject line) to facilitate tracking. For instance, +here's what we see in a 3.x-stable release:: + + Date: Tue Oct 7 07:26:38 2014 -0400 + + libata: Un-break ATA blacklist + + commit 1c40279960bcd7d52dbdf1d466b20d24b99176c8 upstream. + +And here's what might appear in an older kernel once a patch is backported:: + + Date: Tue May 13 22:12:27 2008 +0200 + + wireless, airo: waitbusy() won't delay + + [backport of 2.6 commit b7acbdfbd1f277c1eb23f344f899cfa4cd0bf36a] + +Whatever the format, this information provides a valuable help to people +tracking your trees, and to people trying to troubleshoot bugs in your +tree. |