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1da177e4 LT |
1 | |
2 | How to Get Your Change Into the Linux Kernel | |
3 | or | |
4 | Care And Operation Of Your Linus Torvalds | |
5 | ||
6 | ||
7 | ||
8 | For a person or company who wishes to submit a change to the Linux | |
9 | kernel, the process can sometimes be daunting if you're not familiar | |
10 | with "the system." This text is a collection of suggestions which | |
11 | can greatly increase the chances of your change being accepted. | |
12 | ||
bc7455fa RD |
13 | Read Documentation/SubmitChecklist for a list of items to check |
14 | before submitting code. If you are submitting a driver, also read | |
15 | Documentation/SubmittingDrivers. | |
1da177e4 LT |
16 | |
17 | ||
18 | ||
19 | -------------------------------------------- | |
20 | SECTION 1 - CREATING AND SENDING YOUR CHANGE | |
21 | -------------------------------------------- | |
22 | ||
23 | ||
24 | ||
25 | 1) "diff -up" | |
26 | ------------ | |
27 | ||
28 | Use "diff -up" or "diff -uprN" to create patches. | |
29 | ||
30 | All changes to the Linux kernel occur in the form of patches, as | |
31 | generated by diff(1). When creating your patch, make sure to create it | |
32 | in "unified diff" format, as supplied by the '-u' argument to diff(1). | |
33 | Also, please use the '-p' argument which shows which C function each | |
34 | change is in - that makes the resultant diff a lot easier to read. | |
35 | Patches should be based in the root kernel source directory, | |
36 | not in any lower subdirectory. | |
37 | ||
38 | To create a patch for a single file, it is often sufficient to do: | |
39 | ||
84da7c08 | 40 | SRCTREE= linux-2.6 |
1da177e4 LT |
41 | MYFILE= drivers/net/mydriver.c |
42 | ||
43 | cd $SRCTREE | |
44 | cp $MYFILE $MYFILE.orig | |
45 | vi $MYFILE # make your change | |
46 | cd .. | |
47 | diff -up $SRCTREE/$MYFILE{.orig,} > /tmp/patch | |
48 | ||
49 | To create a patch for multiple files, you should unpack a "vanilla", | |
50 | or unmodified kernel source tree, and generate a diff against your | |
51 | own source tree. For example: | |
52 | ||
84da7c08 | 53 | MYSRC= /devel/linux-2.6 |
1da177e4 | 54 | |
84da7c08 RD |
55 | tar xvfz linux-2.6.12.tar.gz |
56 | mv linux-2.6.12 linux-2.6.12-vanilla | |
57 | diff -uprN -X linux-2.6.12-vanilla/Documentation/dontdiff \ | |
58 | linux-2.6.12-vanilla $MYSRC > /tmp/patch | |
1da177e4 LT |
59 | |
60 | "dontdiff" is a list of files which are generated by the kernel during | |
61 | the build process, and should be ignored in any diff(1)-generated | |
84da7c08 RD |
62 | patch. The "dontdiff" file is included in the kernel tree in |
63 | 2.6.12 and later. For earlier kernel versions, you can get it | |
64 | from <http://www.xenotime.net/linux/doc/dontdiff>. | |
1da177e4 LT |
65 | |
66 | Make sure your patch does not include any extra files which do not | |
67 | belong in a patch submission. Make sure to review your patch -after- | |
68 | generated it with diff(1), to ensure accuracy. | |
69 | ||
70 | If your changes produce a lot of deltas, you may want to look into | |
71 | splitting them into individual patches which modify things in | |
84da7c08 | 72 | logical stages. This will facilitate easier reviewing by other |
1da177e4 | 73 | kernel developers, very important if you want your patch accepted. |
84da7c08 | 74 | There are a number of scripts which can aid in this: |
1da177e4 LT |
75 | |
76 | Quilt: | |
77 | http://savannah.nongnu.org/projects/quilt | |
78 | ||
1da177e4 | 79 | Andrew Morton's patch scripts: |
2223c651 | 80 | http://userweb.kernel.org/~akpm/stuff/patch-scripts.tar.gz |
5b0ed2c6 XVP |
81 | Instead of these scripts, quilt is the recommended patch management |
82 | tool (see above). | |
84da7c08 RD |
83 | |
84 | ||
1da177e4 LT |
85 | |
86 | 2) Describe your changes. | |
87 | ||
88 | Describe the technical detail of the change(s) your patch includes. | |
89 | ||
90 | Be as specific as possible. The WORST descriptions possible include | |
91 | things like "update driver X", "bug fix for driver X", or "this patch | |
92 | includes updates for subsystem X. Please apply." | |
93 | ||
2ae19aca TT |
94 | The maintainer will thank you if you write your patch description in a |
95 | form which can be easily pulled into Linux's source code management | |
96 | system, git, as a "commit log". See #15, below. | |
97 | ||
1da177e4 LT |
98 | If your description starts to get long, that's a sign that you probably |
99 | need to split up your patch. See #3, next. | |
100 | ||
d89b1945 RD |
101 | When you submit or resubmit a patch or patch series, include the |
102 | complete patch description and justification for it. Don't just | |
103 | say that this is version N of the patch (series). Don't expect the | |
104 | patch merger to refer back to earlier patch versions or referenced | |
105 | URLs to find the patch description and put that into the patch. | |
106 | I.e., the patch (series) and its description should be self-contained. | |
107 | This benefits both the patch merger(s) and reviewers. Some reviewers | |
108 | probably didn't even receive earlier versions of the patch. | |
109 | ||
110 | If the patch fixes a logged bug entry, refer to that bug entry by | |
111 | number and URL. | |
1da177e4 LT |
112 | |
113 | ||
114 | 3) Separate your changes. | |
115 | ||
5b0ed2c6 | 116 | Separate _logical changes_ into a single patch file. |
1da177e4 LT |
117 | |
118 | For example, if your changes include both bug fixes and performance | |
119 | enhancements for a single driver, separate those changes into two | |
120 | or more patches. If your changes include an API update, and a new | |
121 | driver which uses that new API, separate those into two patches. | |
122 | ||
123 | On the other hand, if you make a single change to numerous files, | |
124 | group those changes into a single patch. Thus a single logical change | |
125 | is contained within a single patch. | |
126 | ||
127 | If one patch depends on another patch in order for a change to be | |
128 | complete, that is OK. Simply note "this patch depends on patch X" | |
129 | in your patch description. | |
130 | ||
5b0ed2c6 XVP |
131 | If you cannot condense your patch set into a smaller set of patches, |
132 | then only post say 15 or so at a time and wait for review and integration. | |
133 | ||
134 | ||
1da177e4 | 135 | |
0a920b5b AW |
136 | 4) Style check your changes. |
137 | ||
138 | Check your patch for basic style violations, details of which can be | |
139 | found in Documentation/CodingStyle. Failure to do so simply wastes | |
f56d35e7 | 140 | the reviewers time and will get your patch rejected, probably |
0a920b5b AW |
141 | without even being read. |
142 | ||
143 | At a minimum you should check your patches with the patch style | |
a570ab6f | 144 | checker prior to submission (scripts/checkpatch.pl). You should |
0a920b5b AW |
145 | be able to justify all violations that remain in your patch. |
146 | ||
147 | ||
148 | ||
149 | 5) Select e-mail destination. | |
1da177e4 LT |
150 | |
151 | Look through the MAINTAINERS file and the source code, and determine | |
152 | if your change applies to a specific subsystem of the kernel, with | |
e52d2e1f MM |
153 | an assigned maintainer. If so, e-mail that person. The script |
154 | scripts/get_maintainer.pl can be very useful at this step. | |
1da177e4 LT |
155 | |
156 | If no maintainer is listed, or the maintainer does not respond, send | |
157 | your patch to the primary Linux kernel developer's mailing list, | |
158 | linux-kernel@vger.kernel.org. Most kernel developers monitor this | |
159 | e-mail list, and can comment on your changes. | |
160 | ||
5b0ed2c6 XVP |
161 | |
162 | Do not send more than 15 patches at once to the vger mailing lists!!! | |
163 | ||
164 | ||
1da177e4 | 165 | Linus Torvalds is the final arbiter of all changes accepted into the |
99ddcc7e LT |
166 | Linux kernel. His e-mail address is <torvalds@linux-foundation.org>. |
167 | He gets a lot of e-mail, so typically you should do your best to -avoid- | |
168 | sending him e-mail. | |
1da177e4 LT |
169 | |
170 | Patches which are bug fixes, are "obvious" changes, or similarly | |
171 | require little discussion should be sent or CC'd to Linus. Patches | |
172 | which require discussion or do not have a clear advantage should | |
173 | usually be sent first to linux-kernel. Only after the patch is | |
174 | discussed should the patch then be submitted to Linus. | |
175 | ||
1da177e4 LT |
176 | |
177 | ||
0a920b5b | 178 | 6) Select your CC (e-mail carbon copy) list. |
1da177e4 LT |
179 | |
180 | Unless you have a reason NOT to do so, CC linux-kernel@vger.kernel.org. | |
181 | ||
182 | Other kernel developers besides Linus need to be aware of your change, | |
183 | so that they may comment on it and offer code review and suggestions. | |
184 | linux-kernel is the primary Linux kernel developer mailing list. | |
185 | Other mailing lists are available for specific subsystems, such as | |
186 | USB, framebuffer devices, the VFS, the SCSI subsystem, etc. See the | |
187 | MAINTAINERS file for a mailing list that relates specifically to | |
188 | your change. | |
189 | ||
5b0ed2c6 XVP |
190 | Majordomo lists of VGER.KERNEL.ORG at: |
191 | <http://vger.kernel.org/vger-lists.html> | |
192 | ||
1caf1f0f PJ |
193 | If changes affect userland-kernel interfaces, please send |
194 | the MAN-PAGES maintainer (as listed in the MAINTAINERS file) | |
195 | a man-pages patch, or at least a notification of the change, | |
196 | so that some information makes its way into the manual pages. | |
197 | ||
8103b5cc | 198 | Even if the maintainer did not respond in step #5, make sure to ALWAYS |
1da177e4 LT |
199 | copy the maintainer when you change their code. |
200 | ||
201 | For small patches you may want to CC the Trivial Patch Monkey | |
82d27b2b MH |
202 | trivial@kernel.org which collects "trivial" patches. Have a look |
203 | into the MAINTAINERS file for its current manager. | |
204 | Trivial patches must qualify for one of the following rules: | |
1da177e4 | 205 | Spelling fixes in documentation |
8e9cb8fd | 206 | Spelling fixes which could break grep(1) |
1da177e4 LT |
207 | Warning fixes (cluttering with useless warnings is bad) |
208 | Compilation fixes (only if they are actually correct) | |
209 | Runtime fixes (only if they actually fix things) | |
8e9cb8fd | 210 | Removing use of deprecated functions/macros (eg. check_region) |
1da177e4 LT |
211 | Contact detail and documentation fixes |
212 | Non-portable code replaced by portable code (even in arch-specific, | |
213 | since people copy, as long as it's trivial) | |
8e9cb8fd | 214 | Any fix by the author/maintainer of the file (ie. patch monkey |
1da177e4 | 215 | in re-transmission mode) |
84da7c08 | 216 | |
1da177e4 LT |
217 | |
218 | ||
0a920b5b | 219 | 7) No MIME, no links, no compression, no attachments. Just plain text. |
1da177e4 LT |
220 | |
221 | Linus and other kernel developers need to be able to read and comment | |
222 | on the changes you are submitting. It is important for a kernel | |
223 | developer to be able to "quote" your changes, using standard e-mail | |
224 | tools, so that they may comment on specific portions of your code. | |
225 | ||
226 | For this reason, all patches should be submitting e-mail "inline". | |
227 | WARNING: Be wary of your editor's word-wrap corrupting your patch, | |
228 | if you choose to cut-n-paste your patch. | |
229 | ||
230 | Do not attach the patch as a MIME attachment, compressed or not. | |
231 | Many popular e-mail applications will not always transmit a MIME | |
232 | attachment as plain text, making it impossible to comment on your | |
233 | code. A MIME attachment also takes Linus a bit more time to process, | |
234 | decreasing the likelihood of your MIME-attached change being accepted. | |
235 | ||
236 | Exception: If your mailer is mangling patches then someone may ask | |
237 | you to re-send them using MIME. | |
238 | ||
097091c0 MO |
239 | See Documentation/email-clients.txt for hints about configuring |
240 | your e-mail client so that it sends your patches untouched. | |
1da177e4 | 241 | |
0a920b5b | 242 | 8) E-mail size. |
1da177e4 | 243 | |
0a920b5b | 244 | When sending patches to Linus, always follow step #7. |
1da177e4 LT |
245 | |
246 | Large changes are not appropriate for mailing lists, and some | |
4932be77 | 247 | maintainers. If your patch, uncompressed, exceeds 300 kB in size, |
1da177e4 LT |
248 | it is preferred that you store your patch on an Internet-accessible |
249 | server, and provide instead a URL (link) pointing to your patch. | |
250 | ||
251 | ||
252 | ||
0a920b5b | 253 | 9) Name your kernel version. |
1da177e4 LT |
254 | |
255 | It is important to note, either in the subject line or in the patch | |
256 | description, the kernel version to which this patch applies. | |
257 | ||
258 | If the patch does not apply cleanly to the latest kernel version, | |
259 | Linus will not apply it. | |
260 | ||
261 | ||
262 | ||
0a920b5b | 263 | 10) Don't get discouraged. Re-submit. |
1da177e4 LT |
264 | |
265 | After you have submitted your change, be patient and wait. If Linus | |
266 | likes your change and applies it, it will appear in the next version | |
267 | of the kernel that he releases. | |
268 | ||
269 | However, if your change doesn't appear in the next version of the | |
270 | kernel, there could be any number of reasons. It's YOUR job to | |
271 | narrow down those reasons, correct what was wrong, and submit your | |
272 | updated change. | |
273 | ||
274 | It is quite common for Linus to "drop" your patch without comment. | |
275 | That's the nature of the system. If he drops your patch, it could be | |
276 | due to | |
8e9cb8fd | 277 | * Your patch did not apply cleanly to the latest kernel version. |
1da177e4 | 278 | * Your patch was not sufficiently discussed on linux-kernel. |
8e9cb8fd PM |
279 | * A style issue (see section 2). |
280 | * An e-mail formatting issue (re-read this section). | |
281 | * A technical problem with your change. | |
282 | * He gets tons of e-mail, and yours got lost in the shuffle. | |
283 | * You are being annoying. | |
1da177e4 LT |
284 | |
285 | When in doubt, solicit comments on linux-kernel mailing list. | |
286 | ||
287 | ||
288 | ||
0a920b5b | 289 | 11) Include PATCH in the subject |
1da177e4 LT |
290 | |
291 | Due to high e-mail traffic to Linus, and to linux-kernel, it is common | |
292 | convention to prefix your subject line with [PATCH]. This lets Linus | |
293 | and other kernel developers more easily distinguish patches from other | |
294 | e-mail discussions. | |
295 | ||
296 | ||
297 | ||
0a920b5b | 298 | 12) Sign your work |
1da177e4 LT |
299 | |
300 | To improve tracking of who did what, especially with patches that can | |
301 | percolate to their final resting place in the kernel through several | |
302 | layers of maintainers, we've introduced a "sign-off" procedure on | |
303 | patches that are being emailed around. | |
304 | ||
305 | The sign-off is a simple line at the end of the explanation for the | |
306 | patch, which certifies that you wrote it or otherwise have the right to | |
db12fb83 | 307 | pass it on as an open-source patch. The rules are pretty simple: if you |
1da177e4 LT |
308 | can certify the below: |
309 | ||
cbd83da8 | 310 | Developer's Certificate of Origin 1.1 |
1da177e4 LT |
311 | |
312 | By making a contribution to this project, I certify that: | |
313 | ||
314 | (a) The contribution was created in whole or in part by me and I | |
315 | have the right to submit it under the open source license | |
316 | indicated in the file; or | |
317 | ||
318 | (b) The contribution is based upon previous work that, to the best | |
319 | of my knowledge, is covered under an appropriate open source | |
320 | license and I have the right under that license to submit that | |
321 | work with modifications, whether created in whole or in part | |
322 | by me, under the same open source license (unless I am | |
323 | permitted to submit under a different license), as indicated | |
324 | in the file; or | |
325 | ||
326 | (c) The contribution was provided directly to me by some other | |
327 | person who certified (a), (b) or (c) and I have not modified | |
328 | it. | |
329 | ||
cbd83da8 LT |
330 | (d) I understand and agree that this project and the contribution |
331 | are public and that a record of the contribution (including all | |
332 | personal information I submit with it, including my sign-off) is | |
333 | maintained indefinitely and may be redistributed consistent with | |
334 | this project or the open source license(s) involved. | |
335 | ||
1da177e4 LT |
336 | then you just add a line saying |
337 | ||
9fd5559c | 338 | Signed-off-by: Random J Developer <random@developer.example.org> |
1da177e4 | 339 | |
af45f32d GK |
340 | using your real name (sorry, no pseudonyms or anonymous contributions.) |
341 | ||
1da177e4 LT |
342 | Some people also put extra tags at the end. They'll just be ignored for |
343 | now, but you can do this to mark internal company procedures or just | |
344 | point out some special detail about the sign-off. | |
345 | ||
adbd5886 WT |
346 | If you are a subsystem or branch maintainer, sometimes you need to slightly |
347 | modify patches you receive in order to merge them, because the code is not | |
348 | exactly the same in your tree and the submitters'. If you stick strictly to | |
349 | rule (c), you should ask the submitter to rediff, but this is a totally | |
350 | counter-productive waste of time and energy. Rule (b) allows you to adjust | |
351 | the code, but then it is very impolite to change one submitter's code and | |
352 | make him endorse your bugs. To solve this problem, it is recommended that | |
353 | you add a line between the last Signed-off-by header and yours, indicating | |
354 | the nature of your changes. While there is nothing mandatory about this, it | |
355 | seems like prepending the description with your mail and/or name, all | |
356 | enclosed in square brackets, is noticeable enough to make it obvious that | |
357 | you are responsible for last-minute changes. Example : | |
358 | ||
359 | Signed-off-by: Random J Developer <random@developer.example.org> | |
360 | [lucky@maintainer.example.org: struct foo moved from foo.c to foo.h] | |
361 | Signed-off-by: Lucky K Maintainer <lucky@maintainer.example.org> | |
362 | ||
363 | This practise is particularly helpful if you maintain a stable branch and | |
364 | want at the same time to credit the author, track changes, merge the fix, | |
365 | and protect the submitter from complaints. Note that under no circumstances | |
366 | can you change the author's identity (the From header), as it is the one | |
367 | which appears in the changelog. | |
368 | ||
369 | Special note to back-porters: It seems to be a common and useful practise | |
370 | to insert an indication of the origin of a patch at the top of the commit | |
371 | message (just after the subject line) to facilitate tracking. For instance, | |
372 | here's what we see in 2.6-stable : | |
373 | ||
374 | Date: Tue May 13 19:10:30 2008 +0000 | |
375 | ||
376 | SCSI: libiscsi regression in 2.6.25: fix nop timer handling | |
377 | ||
378 | commit 4cf1043593db6a337f10e006c23c69e5fc93e722 upstream | |
379 | ||
380 | And here's what appears in 2.4 : | |
381 | ||
382 | Date: Tue May 13 22:12:27 2008 +0200 | |
383 | ||
384 | wireless, airo: waitbusy() won't delay | |
385 | ||
386 | [backport of 2.6 commit b7acbdfbd1f277c1eb23f344f899cfa4cd0bf36a] | |
387 | ||
388 | Whatever the format, this information provides a valuable help to people | |
389 | tracking your trees, and to people trying to trouble-shoot bugs in your | |
390 | tree. | |
391 | ||
1da177e4 | 392 | |
ef40203a | 393 | 13) When to use Acked-by: and Cc: |
0a920b5b | 394 | |
0f44cd23 AM |
395 | The Signed-off-by: tag indicates that the signer was involved in the |
396 | development of the patch, or that he/she was in the patch's delivery path. | |
397 | ||
398 | If a person was not directly involved in the preparation or handling of a | |
399 | patch but wishes to signify and record their approval of it then they can | |
400 | arrange to have an Acked-by: line added to the patch's changelog. | |
401 | ||
402 | Acked-by: is often used by the maintainer of the affected code when that | |
403 | maintainer neither contributed to nor forwarded the patch. | |
404 | ||
405 | Acked-by: is not as formal as Signed-off-by:. It is a record that the acker | |
406 | has at least reviewed the patch and has indicated acceptance. Hence patch | |
407 | mergers will sometimes manually convert an acker's "yep, looks good to me" | |
408 | into an Acked-by:. | |
409 | ||
410 | Acked-by: does not necessarily indicate acknowledgement of the entire patch. | |
411 | For example, if a patch affects multiple subsystems and has an Acked-by: from | |
412 | one subsystem maintainer then this usually indicates acknowledgement of just | |
413 | the part which affects that maintainer's code. Judgement should be used here. | |
ef40203a | 414 | When in doubt people should refer to the original discussion in the mailing |
0f44cd23 AM |
415 | list archives. |
416 | ||
ef40203a JC |
417 | If a person has had the opportunity to comment on a patch, but has not |
418 | provided such comments, you may optionally add a "Cc:" tag to the patch. | |
419 | This is the only tag which might be added without an explicit action by the | |
420 | person it names. This tag documents that potentially interested parties | |
421 | have been included in the discussion | |
0f44cd23 | 422 | |
ef40203a | 423 | |
bbb0a424 JC |
424 | 14) Using Reported-by:, Tested-by: and Reviewed-by: |
425 | ||
426 | If this patch fixes a problem reported by somebody else, consider adding a | |
427 | Reported-by: tag to credit the reporter for their contribution. Please | |
428 | note that this tag should not be added without the reporter's permission, | |
429 | especially if the problem was not reported in a public forum. That said, | |
430 | if we diligently credit our bug reporters, they will, hopefully, be | |
431 | inspired to help us again in the future. | |
ef40203a JC |
432 | |
433 | A Tested-by: tag indicates that the patch has been successfully tested (in | |
434 | some environment) by the person named. This tag informs maintainers that | |
435 | some testing has been performed, provides a means to locate testers for | |
436 | future patches, and ensures credit for the testers. | |
437 | ||
438 | Reviewed-by:, instead, indicates that the patch has been reviewed and found | |
439 | acceptable according to the Reviewer's Statement: | |
440 | ||
441 | Reviewer's statement of oversight | |
442 | ||
443 | By offering my Reviewed-by: tag, I state that: | |
444 | ||
445 | (a) I have carried out a technical review of this patch to | |
446 | evaluate its appropriateness and readiness for inclusion into | |
447 | the mainline kernel. | |
448 | ||
449 | (b) Any problems, concerns, or questions relating to the patch | |
450 | have been communicated back to the submitter. I am satisfied | |
451 | with the submitter's response to my comments. | |
452 | ||
453 | (c) While there may be things that could be improved with this | |
454 | submission, I believe that it is, at this time, (1) a | |
455 | worthwhile modification to the kernel, and (2) free of known | |
456 | issues which would argue against its inclusion. | |
457 | ||
458 | (d) While I have reviewed the patch and believe it to be sound, I | |
459 | do not (unless explicitly stated elsewhere) make any | |
460 | warranties or guarantees that it will achieve its stated | |
461 | purpose or function properly in any given situation. | |
462 | ||
463 | A Reviewed-by tag is a statement of opinion that the patch is an | |
464 | appropriate modification of the kernel without any remaining serious | |
465 | technical issues. Any interested reviewer (who has done the work) can | |
466 | offer a Reviewed-by tag for a patch. This tag serves to give credit to | |
467 | reviewers and to inform maintainers of the degree of review which has been | |
468 | done on the patch. Reviewed-by: tags, when supplied by reviewers known to | |
469 | understand the subject area and to perform thorough reviews, will normally | |
5801da1b | 470 | increase the likelihood of your patch getting into the kernel. |
ef40203a JC |
471 | |
472 | ||
473 | 15) The canonical patch format | |
84da7c08 | 474 | |
75f8426c PJ |
475 | The canonical patch subject line is: |
476 | ||
d6b9acc0 | 477 | Subject: [PATCH 001/123] subsystem: summary phrase |
75f8426c PJ |
478 | |
479 | The canonical patch message body contains the following: | |
480 | ||
481 | - A "from" line specifying the patch author. | |
482 | ||
483 | - An empty line. | |
484 | ||
485 | - The body of the explanation, which will be copied to the | |
486 | permanent changelog to describe this patch. | |
487 | ||
488 | - The "Signed-off-by:" lines, described above, which will | |
489 | also go in the changelog. | |
490 | ||
491 | - A marker line containing simply "---". | |
492 | ||
493 | - Any additional comments not suitable for the changelog. | |
494 | ||
495 | - The actual patch (diff output). | |
496 | ||
497 | The Subject line format makes it very easy to sort the emails | |
498 | alphabetically by subject line - pretty much any email reader will | |
499 | support that - since because the sequence number is zero-padded, | |
500 | the numerical and alphabetic sort is the same. | |
501 | ||
d6b9acc0 PJ |
502 | The "subsystem" in the email's Subject should identify which |
503 | area or subsystem of the kernel is being patched. | |
504 | ||
505 | The "summary phrase" in the email's Subject should concisely | |
506 | describe the patch which that email contains. The "summary | |
507 | phrase" should not be a filename. Do not use the same "summary | |
66effdc6 RD |
508 | phrase" for every patch in a whole patch series (where a "patch |
509 | series" is an ordered sequence of multiple, related patches). | |
d6b9acc0 | 510 | |
2ae19aca TT |
511 | Bear in mind that the "summary phrase" of your email becomes a |
512 | globally-unique identifier for that patch. It propagates all the way | |
513 | into the git changelog. The "summary phrase" may later be used in | |
514 | developer discussions which refer to the patch. People will want to | |
515 | google for the "summary phrase" to read discussion regarding that | |
516 | patch. It will also be the only thing that people may quickly see | |
517 | when, two or three months later, they are going through perhaps | |
518 | thousands of patches using tools such as "gitk" or "git log | |
519 | --oneline". | |
520 | ||
521 | For these reasons, the "summary" must be no more than 70-75 | |
522 | characters, and it must describe both what the patch changes, as well | |
523 | as why the patch might be necessary. It is challenging to be both | |
524 | succinct and descriptive, but that is what a well-written summary | |
525 | should do. | |
526 | ||
527 | The "summary phrase" may be prefixed by tags enclosed in square | |
528 | brackets: "Subject: [PATCH tag] <summary phrase>". The tags are not | |
529 | considered part of the summary phrase, but describe how the patch | |
530 | should be treated. Common tags might include a version descriptor if | |
531 | the multiple versions of the patch have been sent out in response to | |
532 | comments (i.e., "v1, v2, v3"), or "RFC" to indicate a request for | |
533 | comments. If there are four patches in a patch series the individual | |
534 | patches may be numbered like this: 1/4, 2/4, 3/4, 4/4. This assures | |
535 | that developers understand the order in which the patches should be | |
536 | applied and that they have reviewed or applied all of the patches in | |
537 | the patch series. | |
d6b9acc0 PJ |
538 | |
539 | A couple of example Subjects: | |
540 | ||
541 | Subject: [patch 2/5] ext2: improve scalability of bitmap searching | |
542 | Subject: [PATCHv2 001/207] x86: fix eflags tracking | |
75f8426c PJ |
543 | |
544 | The "from" line must be the very first line in the message body, | |
545 | and has the form: | |
546 | ||
547 | From: Original Author <author@example.com> | |
548 | ||
549 | The "from" line specifies who will be credited as the author of the | |
550 | patch in the permanent changelog. If the "from" line is missing, | |
551 | then the "From:" line from the email header will be used to determine | |
552 | the patch author in the changelog. | |
553 | ||
554 | The explanation body will be committed to the permanent source | |
555 | changelog, so should make sense to a competent reader who has long | |
556 | since forgotten the immediate details of the discussion that might | |
2ae19aca TT |
557 | have led to this patch. Including symptoms of the failure which the |
558 | patch addresses (kernel log messages, oops messages, etc.) is | |
559 | especially useful for people who might be searching the commit logs | |
560 | looking for the applicable patch. If a patch fixes a compile failure, | |
561 | it may not be necessary to include _all_ of the compile failures; just | |
562 | enough that it is likely that someone searching for the patch can find | |
563 | it. As in the "summary phrase", it is important to be both succinct as | |
564 | well as descriptive. | |
75f8426c PJ |
565 | |
566 | The "---" marker line serves the essential purpose of marking for patch | |
567 | handling tools where the changelog message ends. | |
568 | ||
569 | One good use for the additional comments after the "---" marker is for | |
2ae19aca TT |
570 | a diffstat, to show what files have changed, and the number of |
571 | inserted and deleted lines per file. A diffstat is especially useful | |
572 | on bigger patches. Other comments relevant only to the moment or the | |
573 | maintainer, not suitable for the permanent changelog, should also go | |
574 | here. A good example of such comments might be "patch changelogs" | |
575 | which describe what has changed between the v1 and v2 version of the | |
576 | patch. | |
577 | ||
578 | If you are going to include a diffstat after the "---" marker, please | |
579 | use diffstat options "-p 1 -w 70" so that filenames are listed from | |
580 | the top of the kernel source tree and don't use too much horizontal | |
581 | space (easily fit in 80 columns, maybe with some indentation). | |
75f8426c PJ |
582 | |
583 | See more details on the proper patch format in the following | |
584 | references. | |
585 | ||
586 | ||
14863617 | 587 | 16) Sending "git pull" requests (from Linus emails) |
84da7c08 | 588 | |
14863617 RD |
589 | Please write the git repo address and branch name alone on the same line |
590 | so that I can't even by mistake pull from the wrong branch, and so | |
591 | that a triple-click just selects the whole thing. | |
592 | ||
593 | So the proper format is something along the lines of: | |
594 | ||
595 | "Please pull from | |
596 | ||
597 | git://jdelvare.pck.nerim.net/jdelvare-2.6 i2c-for-linus | |
598 | ||
599 | to get these changes:" | |
600 | ||
601 | so that I don't have to hunt-and-peck for the address and inevitably | |
602 | get it wrong (actually, I've only gotten it wrong a few times, and | |
603 | checking against the diffstat tells me when I get it wrong, but I'm | |
604 | just a lot more comfortable when I don't have to "look for" the right | |
605 | thing to pull, and double-check that I have the right branch-name). | |
606 | ||
607 | ||
608 | Please use "git diff -M --stat --summary" to generate the diffstat: | |
609 | the -M enables rename detection, and the summary enables a summary of | |
610 | new/deleted or renamed files. | |
611 | ||
612 | With rename detection, the statistics are rather different [...] | |
613 | because git will notice that a fair number of the changes are renames. | |
84da7c08 | 614 | |
1da177e4 LT |
615 | ----------------------------------- |
616 | SECTION 2 - HINTS, TIPS, AND TRICKS | |
617 | ----------------------------------- | |
618 | ||
619 | This section lists many of the common "rules" associated with code | |
620 | submitted to the kernel. There are always exceptions... but you must | |
621 | have a really good reason for doing so. You could probably call this | |
622 | section Linus Computer Science 101. | |
623 | ||
624 | ||
625 | ||
626 | 1) Read Documentation/CodingStyle | |
627 | ||
628 | Nuff said. If your code deviates too much from this, it is likely | |
629 | to be rejected without further review, and without comment. | |
630 | ||
5ab3bd57 KK |
631 | One significant exception is when moving code from one file to |
632 | another -- in this case you should not modify the moved code at all in | |
de7d4f0e AW |
633 | the same patch which moves it. This clearly delineates the act of |
634 | moving the code and your changes. This greatly aids review of the | |
635 | actual differences and allows tools to better track the history of | |
636 | the code itself. | |
637 | ||
0a920b5b | 638 | Check your patches with the patch style checker prior to submission |
de7d4f0e AW |
639 | (scripts/checkpatch.pl). The style checker should be viewed as |
640 | a guide not as the final word. If your code looks better with | |
641 | a violation then its probably best left alone. | |
642 | ||
643 | The checker reports at three levels: | |
644 | - ERROR: things that are very likely to be wrong | |
645 | - WARNING: things requiring careful review | |
646 | - CHECK: things requiring thought | |
647 | ||
648 | You should be able to justify all violations that remain in your | |
649 | patch. | |
0a920b5b | 650 | |
1da177e4 LT |
651 | |
652 | ||
653 | 2) #ifdefs are ugly | |
654 | ||
655 | Code cluttered with ifdefs is difficult to read and maintain. Don't do | |
656 | it. Instead, put your ifdefs in a header, and conditionally define | |
657 | 'static inline' functions, or macros, which are used in the code. | |
658 | Let the compiler optimize away the "no-op" case. | |
659 | ||
660 | Simple example, of poor code: | |
661 | ||
662 | dev = alloc_etherdev (sizeof(struct funky_private)); | |
663 | if (!dev) | |
664 | return -ENODEV; | |
665 | #ifdef CONFIG_NET_FUNKINESS | |
666 | init_funky_net(dev); | |
667 | #endif | |
668 | ||
669 | Cleaned-up example: | |
670 | ||
671 | (in header) | |
672 | #ifndef CONFIG_NET_FUNKINESS | |
673 | static inline void init_funky_net (struct net_device *d) {} | |
674 | #endif | |
675 | ||
676 | (in the code itself) | |
677 | dev = alloc_etherdev (sizeof(struct funky_private)); | |
678 | if (!dev) | |
679 | return -ENODEV; | |
680 | init_funky_net(dev); | |
681 | ||
682 | ||
683 | ||
684 | 3) 'static inline' is better than a macro | |
685 | ||
686 | Static inline functions are greatly preferred over macros. | |
687 | They provide type safety, have no length limitations, no formatting | |
688 | limitations, and under gcc they are as cheap as macros. | |
689 | ||
690 | Macros should only be used for cases where a static inline is clearly | |
f2b2ea69 | 691 | suboptimal [there are a few, isolated cases of this in fast paths], |
1da177e4 LT |
692 | or where it is impossible to use a static inline function [such as |
693 | string-izing]. | |
694 | ||
695 | 'static inline' is preferred over 'static __inline__', 'extern inline', | |
696 | and 'extern __inline__'. | |
697 | ||
698 | ||
699 | ||
700 | 4) Don't over-design. | |
701 | ||
702 | Don't try to anticipate nebulous future cases which may or may not | |
84da7c08 | 703 | be useful: "Make it as simple as you can, and no simpler." |
1da177e4 | 704 | |
5b0ed2c6 XVP |
705 | |
706 | ||
707 | ---------------------- | |
708 | SECTION 3 - REFERENCES | |
709 | ---------------------- | |
710 | ||
711 | Andrew Morton, "The perfect patch" (tpp). | |
2223c651 | 712 | <http://userweb.kernel.org/~akpm/stuff/tpp.txt> |
5b0ed2c6 | 713 | |
8e9cb8fd | 714 | Jeff Garzik, "Linux kernel patch submission format". |
5b0ed2c6 XVP |
715 | <http://linux.yyz.us/patch-format.html> |
716 | ||
8e9cb8fd | 717 | Greg Kroah-Hartman, "How to piss off a kernel subsystem maintainer". |
f5039935 VN |
718 | <http://www.kroah.com/log/linux/maintainer.html> |
719 | <http://www.kroah.com/log/linux/maintainer-02.html> | |
720 | <http://www.kroah.com/log/linux/maintainer-03.html> | |
721 | <http://www.kroah.com/log/linux/maintainer-04.html> | |
722 | <http://www.kroah.com/log/linux/maintainer-05.html> | |
5b0ed2c6 | 723 | |
bc7455fa | 724 | NO!!!! No more huge patch bombs to linux-kernel@vger.kernel.org people! |
5b0ed2c6 XVP |
725 | <http://marc.theaimsgroup.com/?l=linux-kernel&m=112112749912944&w=2> |
726 | ||
8e9cb8fd | 727 | Kernel Documentation/CodingStyle: |
4db29c17 | 728 | <http://users.sosdg.org/~qiyong/lxr/source/Documentation/CodingStyle> |
5b0ed2c6 | 729 | |
8e9cb8fd | 730 | Linus Torvalds's mail on the canonical patch format: |
5b0ed2c6 | 731 | <http://lkml.org/lkml/2005/4/7/183> |
9536727e AK |
732 | |
733 | Andi Kleen, "On submitting kernel patches" | |
25985edc | 734 | Some strategies to get difficult or controversial changes in. |
9536727e AK |
735 | http://halobates.de/on-submitting-patches.pdf |
736 | ||
5b0ed2c6 | 737 | -- |