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1 | .. _modifyingpatches: |
2 | ||
3 | Modifying Patches | |
4 | ================= | |
5 | ||
6 | If you are a subsystem or branch maintainer, sometimes you need to slightly | |
7 | modify patches you receive in order to merge them, because the code is not | |
8 | exactly the same in your tree and the submitters'. If you stick strictly to | |
9 | rule (c) of the developers certificate of origin, you should ask the submitter | |
10 | to rediff, but this is a totally counter-productive waste of time and energy. | |
11 | Rule (b) allows you to adjust the code, but then it is very impolite to change | |
12 | one submitters code and make him endorse your bugs. To solve this problem, it | |
13 | is recommended that you add a line between the last Signed-off-by header and | |
14 | yours, indicating the nature of your changes. While there is nothing mandatory | |
15 | about this, it seems like prepending the description with your mail and/or | |
16 | name, all enclosed in square brackets, is noticeable enough to make it obvious | |
17 | that you are responsible for last-minute changes. Example:: | |
18 | ||
19 | Signed-off-by: Random J Developer <random@developer.example.org> | |
20 | [lucky@maintainer.example.org: struct foo moved from foo.c to foo.h] | |
21 | Signed-off-by: Lucky K Maintainer <lucky@maintainer.example.org> | |
22 | ||
23 | This practice is particularly helpful if you maintain a stable branch and | |
24 | want at the same time to credit the author, track changes, merge the fix, | |
25 | and protect the submitter from complaints. Note that under no circumstances | |
26 | can you change the author's identity (the From header), as it is the one | |
27 | which appears in the changelog. | |
28 | ||
29 | Special note to back-porters: It seems to be a common and useful practice | |
30 | to insert an indication of the origin of a patch at the top of the commit | |
31 | message (just after the subject line) to facilitate tracking. For instance, | |
32 | here's what we see in a 3.x-stable release:: | |
33 | ||
34 | Date: Tue Oct 7 07:26:38 2014 -0400 | |
35 | ||
36 | libata: Un-break ATA blacklist | |
37 | ||
38 | commit 1c40279960bcd7d52dbdf1d466b20d24b99176c8 upstream. | |
39 | ||
40 | And here's what might appear in an older kernel once a patch is backported:: | |
41 | ||
42 | Date: Tue May 13 22:12:27 2008 +0200 | |
43 | ||
44 | wireless, airo: waitbusy() won't delay | |
45 | ||
46 | [backport of 2.6 commit b7acbdfbd1f277c1eb23f344f899cfa4cd0bf36a] | |
47 | ||
48 | Whatever the format, this information provides a valuable help to people | |
49 | tracking your trees, and to people trying to troubleshoot bugs in your | |
50 | tree. |