The repeated sign-offs necessary when a subsystem maintainer modifies an incoming patch has been moved from submitting-patches.rst to Documentation/maintainer, since the affairs of a subsystem maintainer are not especially relevant to someone reading a guide for how to submit their first patch. Signed-off-by: Drew DeVault <sir@cmpwn.com> Link: https://lore.kernel.org/r/20200903160545.83185-4-sir@cmpwn.com Signed-off-by: Jonathan Corbet <corbet@lwn.net>
		
			
				
	
	
		
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.. _modifyingpatches:
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Modifying Patches
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=================
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If you are a subsystem or branch maintainer, sometimes you need to slightly
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modify patches you receive in order to merge them, because the code is not
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exactly the same in your tree and the submitters'. If you stick strictly to
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rule (c) of the developers certificate of origin, you should ask the submitter
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to rediff, but this is a totally counter-productive waste of time and energy.
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Rule (b) allows you to adjust the code, but then it is very impolite to change
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one submitters code and make him endorse your bugs. To solve this problem, it
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is recommended that you add a line between the last Signed-off-by header and
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yours, indicating the nature of your changes. While there is nothing mandatory
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about this, it seems like prepending the description with your mail and/or
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name, all enclosed in square brackets, is noticeable enough to make it obvious
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that you are responsible for last-minute changes. Example::
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       Signed-off-by: Random J Developer <random@developer.example.org>
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       [lucky@maintainer.example.org: struct foo moved from foo.c to foo.h]
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       Signed-off-by: Lucky K Maintainer <lucky@maintainer.example.org>
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This practice is particularly helpful if you maintain a stable branch and
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want at the same time to credit the author, track changes, merge the fix,
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and protect the submitter from complaints. Note that under no circumstances
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can you change the author's identity (the From header), as it is the one
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which appears in the changelog.
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Special note to back-porters: It seems to be a common and useful practice
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to insert an indication of the origin of a patch at the top of the commit
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message (just after the subject line) to facilitate tracking. For instance,
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here's what we see in a 3.x-stable release::
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  Date:   Tue Oct 7 07:26:38 2014 -0400
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    libata: Un-break ATA blacklist
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    commit 1c40279960bcd7d52dbdf1d466b20d24b99176c8 upstream.
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And here's what might appear in an older kernel once a patch is backported::
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    Date:   Tue May 13 22:12:27 2008 +0200
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        wireless, airo: waitbusy() won't delay
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        [backport of 2.6 commit b7acbdfbd1f277c1eb23f344f899cfa4cd0bf36a]
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Whatever the format, this information provides a valuable help to people
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tracking your trees, and to people trying to troubleshoot bugs in your
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tree.
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