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Linux/Documentation/SubmittingPatches

  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 
 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.
 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 
 40         SRCTREE= linux-2.6
 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 
 53         MYSRC= /devel/linux-2.6
 54 
 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
 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
 62 patch.  The "dontdiff" file is included in the kernel tree in
 63 2.6.12 and later.
 64 
 65 Make sure your patch does not include any extra files which do not
 66 belong in a patch submission.  Make sure to review your patch -after-
 67 generated it with diff(1), to ensure accuracy.
 68 
 69 If your changes produce a lot of deltas, you may want to look into
 70 splitting them into individual patches which modify things in
 71 logical stages.  This will facilitate easier reviewing by other
 72 kernel developers, very important if you want your patch accepted.
 73 There are a number of scripts which can aid in this:
 74 
 75 Quilt:
 76 http://savannah.nongnu.org/projects/quilt
 77 
 78 Andrew Morton's patch scripts:
 79 http://userweb.kernel.org/~akpm/stuff/patch-scripts.tar.gz
 80 Instead of these scripts, quilt is the recommended patch management
 81 tool (see above).
 82 
 83 
 84 
 85 2) Describe your changes.
 86 
 87 Describe the technical detail of the change(s) your patch includes.
 88 
 89 Be as specific as possible.  The WORST descriptions possible include
 90 things like "update driver X", "bug fix for driver X", or "this patch
 91 includes updates for subsystem X.  Please apply."
 92 
 93 The maintainer will thank you if you write your patch description in a
 94 form which can be easily pulled into Linux's source code management
 95 system, git, as a "commit log".  See #15, below.
 96 
 97 If your description starts to get long, that's a sign that you probably
 98 need to split up your patch.  See #3, next.
 99 
100 When you submit or resubmit a patch or patch series, include the
101 complete patch description and justification for it.  Don't just
102 say that this is version N of the patch (series).  Don't expect the
103 patch merger to refer back to earlier patch versions or referenced
104 URLs to find the patch description and put that into the patch.
105 I.e., the patch (series) and its description should be self-contained.
106 This benefits both the patch merger(s) and reviewers.  Some reviewers
107 probably didn't even receive earlier versions of the patch.
108 
109 If the patch fixes a logged bug entry, refer to that bug entry by
110 number and URL.
111 
112 If you want to refer to a specific commit, don't just refer to the
113 SHA-1 ID of the commit. Please also include the oneline summary of
114 the commit, to make it easier for reviewers to know what it is about.
115 Example:
116 
117         Commit e21d2170f36602ae2708 ("video: remove unnecessary
118         platform_set_drvdata()") removed the unnecessary
119         platform_set_drvdata(), but left the variable "dev" unused,
120         delete it.
121 
122 
123 3) Separate your changes.
124 
125 Separate _logical changes_ into a single patch file.
126 
127 For example, if your changes include both bug fixes and performance
128 enhancements for a single driver, separate those changes into two
129 or more patches.  If your changes include an API update, and a new
130 driver which uses that new API, separate those into two patches.
131 
132 On the other hand, if you make a single change to numerous files,
133 group those changes into a single patch.  Thus a single logical change
134 is contained within a single patch.
135 
136 If one patch depends on another patch in order for a change to be
137 complete, that is OK.  Simply note "this patch depends on patch X"
138 in your patch description.
139 
140 If you cannot condense your patch set into a smaller set of patches,
141 then only post say 15 or so at a time and wait for review and integration.
142 
143 
144 
145 4) Style check your changes.
146 
147 Check your patch for basic style violations, details of which can be
148 found in Documentation/CodingStyle.  Failure to do so simply wastes
149 the reviewers time and will get your patch rejected, probably
150 without even being read.
151 
152 At a minimum you should check your patches with the patch style
153 checker prior to submission (scripts/checkpatch.pl).  You should
154 be able to justify all violations that remain in your patch.
155 
156 
157 
158 5) Select e-mail destination.
159 
160 Look through the MAINTAINERS file and the source code, and determine
161 if your change applies to a specific subsystem of the kernel, with
162 an assigned maintainer.  If so, e-mail that person.  The script
163 scripts/get_maintainer.pl can be very useful at this step.
164 
165 If no maintainer is listed, or the maintainer does not respond, send
166 your patch to the primary Linux kernel developer's mailing list,
167 linux-kernel@vger.kernel.org.  Most kernel developers monitor this
168 e-mail list, and can comment on your changes.
169 
170 
171 Do not send more than 15 patches at once to the vger mailing lists!!!
172 
173 
174 Linus Torvalds is the final arbiter of all changes accepted into the
175 Linux kernel.  His e-mail address is <torvalds@linux-foundation.org>. 
176 He gets a lot of e-mail, so typically you should do your best to -avoid-
177 sending him e-mail. 
178 
179 Patches which are bug fixes, are "obvious" changes, or similarly
180 require little discussion should be sent or CC'd to Linus.  Patches
181 which require discussion or do not have a clear advantage should
182 usually be sent first to linux-kernel.  Only after the patch is
183 discussed should the patch then be submitted to Linus.
184 
185 
186 
187 6) Select your CC (e-mail carbon copy) list.
188 
189 Unless you have a reason NOT to do so, CC linux-kernel@vger.kernel.org.
190 
191 Other kernel developers besides Linus need to be aware of your change,
192 so that they may comment on it and offer code review and suggestions.
193 linux-kernel is the primary Linux kernel developer mailing list.
194 Other mailing lists are available for specific subsystems, such as
195 USB, framebuffer devices, the VFS, the SCSI subsystem, etc.  See the
196 MAINTAINERS file for a mailing list that relates specifically to
197 your change.
198 
199 Majordomo lists of VGER.KERNEL.ORG at:
200         <http://vger.kernel.org/vger-lists.html>
201 
202 If changes affect userland-kernel interfaces, please send
203 the MAN-PAGES maintainer (as listed in the MAINTAINERS file)
204 a man-pages patch, or at least a notification of the change,
205 so that some information makes its way into the manual pages.
206 
207 Even if the maintainer did not respond in step #5, make sure to ALWAYS
208 copy the maintainer when you change their code.
209 
210 For small patches you may want to CC the Trivial Patch Monkey
211 trivial@kernel.org which collects "trivial" patches. Have a look
212 into the MAINTAINERS file for its current manager.
213 Trivial patches must qualify for one of the following rules:
214  Spelling fixes in documentation
215  Spelling fixes which could break grep(1)
216  Warning fixes (cluttering with useless warnings is bad)
217  Compilation fixes (only if they are actually correct)
218  Runtime fixes (only if they actually fix things)
219  Removing use of deprecated functions/macros (eg. check_region)
220  Contact detail and documentation fixes
221  Non-portable code replaced by portable code (even in arch-specific,
222  since people copy, as long as it's trivial)
223  Any fix by the author/maintainer of the file (ie. patch monkey
224  in re-transmission mode)
225 
226 
227 
228 7) No MIME, no links, no compression, no attachments.  Just plain text.
229 
230 Linus and other kernel developers need to be able to read and comment
231 on the changes you are submitting.  It is important for a kernel
232 developer to be able to "quote" your changes, using standard e-mail
233 tools, so that they may comment on specific portions of your code.
234 
235 For this reason, all patches should be submitting e-mail "inline".
236 WARNING:  Be wary of your editor's word-wrap corrupting your patch,
237 if you choose to cut-n-paste your patch.
238 
239 Do not attach the patch as a MIME attachment, compressed or not.
240 Many popular e-mail applications will not always transmit a MIME
241 attachment as plain text, making it impossible to comment on your
242 code.  A MIME attachment also takes Linus a bit more time to process,
243 decreasing the likelihood of your MIME-attached change being accepted.
244 
245 Exception:  If your mailer is mangling patches then someone may ask
246 you to re-send them using MIME.
247 
248 See Documentation/email-clients.txt for hints about configuring
249 your e-mail client so that it sends your patches untouched.
250 
251 8) E-mail size.
252 
253 When sending patches to Linus, always follow step #7.
254 
255 Large changes are not appropriate for mailing lists, and some
256 maintainers.  If your patch, uncompressed, exceeds 300 kB in size,
257 it is preferred that you store your patch on an Internet-accessible
258 server, and provide instead a URL (link) pointing to your patch.
259 
260 
261 
262 9) Name your kernel version.
263 
264 It is important to note, either in the subject line or in the patch
265 description, the kernel version to which this patch applies.
266 
267 If the patch does not apply cleanly to the latest kernel version,
268 Linus will not apply it.
269 
270 
271 
272 10) Don't get discouraged.  Re-submit.
273 
274 After you have submitted your change, be patient and wait.  If Linus
275 likes your change and applies it, it will appear in the next version
276 of the kernel that he releases.
277 
278 However, if your change doesn't appear in the next version of the
279 kernel, there could be any number of reasons.  It's YOUR job to
280 narrow down those reasons, correct what was wrong, and submit your
281 updated change.
282 
283 It is quite common for Linus to "drop" your patch without comment.
284 That's the nature of the system.  If he drops your patch, it could be
285 due to
286 * Your patch did not apply cleanly to the latest kernel version.
287 * Your patch was not sufficiently discussed on linux-kernel.
288 * A style issue (see section 2).
289 * An e-mail formatting issue (re-read this section).
290 * A technical problem with your change.
291 * He gets tons of e-mail, and yours got lost in the shuffle.
292 * You are being annoying.
293 
294 When in doubt, solicit comments on linux-kernel mailing list.
295 
296 
297 
298 11) Include PATCH in the subject
299 
300 Due to high e-mail traffic to Linus, and to linux-kernel, it is common
301 convention to prefix your subject line with [PATCH].  This lets Linus
302 and other kernel developers more easily distinguish patches from other
303 e-mail discussions.
304 
305 
306 
307 12) Sign your work
308 
309 To improve tracking of who did what, especially with patches that can
310 percolate to their final resting place in the kernel through several
311 layers of maintainers, we've introduced a "sign-off" procedure on
312 patches that are being emailed around.
313 
314 The sign-off is a simple line at the end of the explanation for the
315 patch, which certifies that you wrote it or otherwise have the right to
316 pass it on as an open-source patch.  The rules are pretty simple: if you
317 can certify the below:
318 
319         Developer's Certificate of Origin 1.1
320 
321         By making a contribution to this project, I certify that:
322 
323         (a) The contribution was created in whole or in part by me and I
324             have the right to submit it under the open source license
325             indicated in the file; or
326 
327         (b) The contribution is based upon previous work that, to the best
328             of my knowledge, is covered under an appropriate open source
329             license and I have the right under that license to submit that
330             work with modifications, whether created in whole or in part
331             by me, under the same open source license (unless I am
332             permitted to submit under a different license), as indicated
333             in the file; or
334 
335         (c) The contribution was provided directly to me by some other
336             person who certified (a), (b) or (c) and I have not modified
337             it.
338 
339         (d) I understand and agree that this project and the contribution
340             are public and that a record of the contribution (including all
341             personal information I submit with it, including my sign-off) is
342             maintained indefinitely and may be redistributed consistent with
343             this project or the open source license(s) involved.
344 
345 then you just add a line saying
346 
347         Signed-off-by: Random J Developer <random@developer.example.org>
348 
349 using your real name (sorry, no pseudonyms or anonymous contributions.)
350 
351 Some people also put extra tags at the end.  They'll just be ignored for
352 now, but you can do this to mark internal company procedures or just
353 point out some special detail about the sign-off. 
354 
355 If you are a subsystem or branch maintainer, sometimes you need to slightly
356 modify patches you receive in order to merge them, because the code is not
357 exactly the same in your tree and the submitters'. If you stick strictly to
358 rule (c), you should ask the submitter to rediff, but this is a totally
359 counter-productive waste of time and energy. Rule (b) allows you to adjust
360 the code, but then it is very impolite to change one submitter's code and
361 make him endorse your bugs. To solve this problem, it is recommended that
362 you add a line between the last Signed-off-by header and yours, indicating
363 the nature of your changes. While there is nothing mandatory about this, it
364 seems like prepending the description with your mail and/or name, all
365 enclosed in square brackets, is noticeable enough to make it obvious that
366 you are responsible for last-minute changes. Example :
367 
368         Signed-off-by: Random J Developer <random@developer.example.org>
369         [lucky@maintainer.example.org: struct foo moved from foo.c to foo.h]
370         Signed-off-by: Lucky K Maintainer <lucky@maintainer.example.org>
371 
372 This practise is particularly helpful if you maintain a stable branch and
373 want at the same time to credit the author, track changes, merge the fix,
374 and protect the submitter from complaints. Note that under no circumstances
375 can you change the author's identity (the From header), as it is the one
376 which appears in the changelog.
377 
378 Special note to back-porters: It seems to be a common and useful practise
379 to insert an indication of the origin of a patch at the top of the commit
380 message (just after the subject line) to facilitate tracking. For instance,
381 here's what we see in 2.6-stable :
382 
383     Date:   Tue May 13 19:10:30 2008 +0000
384 
385         SCSI: libiscsi regression in 2.6.25: fix nop timer handling
386 
387         commit 4cf1043593db6a337f10e006c23c69e5fc93e722 upstream
388 
389 And here's what appears in 2.4 :
390 
391     Date:   Tue May 13 22:12:27 2008 +0200
392 
393         wireless, airo: waitbusy() won't delay
394 
395         [backport of 2.6 commit b7acbdfbd1f277c1eb23f344f899cfa4cd0bf36a]
396 
397 Whatever the format, this information provides a valuable help to people
398 tracking your trees, and to people trying to trouble-shoot bugs in your
399 tree.
400 
401 
402 13) When to use Acked-by: and Cc:
403 
404 The Signed-off-by: tag indicates that the signer was involved in the
405 development of the patch, or that he/she was in the patch's delivery path.
406 
407 If a person was not directly involved in the preparation or handling of a
408 patch but wishes to signify and record their approval of it then they can
409 arrange to have an Acked-by: line added to the patch's changelog.
410 
411 Acked-by: is often used by the maintainer of the affected code when that
412 maintainer neither contributed to nor forwarded the patch.
413 
414 Acked-by: is not as formal as Signed-off-by:.  It is a record that the acker
415 has at least reviewed the patch and has indicated acceptance.  Hence patch
416 mergers will sometimes manually convert an acker's "yep, looks good to me"
417 into an Acked-by:.
418 
419 Acked-by: does not necessarily indicate acknowledgement of the entire patch.
420 For example, if a patch affects multiple subsystems and has an Acked-by: from
421 one subsystem maintainer then this usually indicates acknowledgement of just
422 the part which affects that maintainer's code.  Judgement should be used here.
423 When in doubt people should refer to the original discussion in the mailing
424 list archives.
425 
426 If a person has had the opportunity to comment on a patch, but has not
427 provided such comments, you may optionally add a "Cc:" tag to the patch.
428 This is the only tag which might be added without an explicit action by the
429 person it names.  This tag documents that potentially interested parties
430 have been included in the discussion
431 
432 
433 14) Using Reported-by:, Tested-by:, Reviewed-by: and Suggested-by:
434 
435 If this patch fixes a problem reported by somebody else, consider adding a
436 Reported-by: tag to credit the reporter for their contribution.  Please
437 note that this tag should not be added without the reporter's permission,
438 especially if the problem was not reported in a public forum.  That said,
439 if we diligently credit our bug reporters, they will, hopefully, be
440 inspired to help us again in the future.
441 
442 A Tested-by: tag indicates that the patch has been successfully tested (in
443 some environment) by the person named.  This tag informs maintainers that
444 some testing has been performed, provides a means to locate testers for
445 future patches, and ensures credit for the testers.
446 
447 Reviewed-by:, instead, indicates that the patch has been reviewed and found
448 acceptable according to the Reviewer's Statement:
449 
450         Reviewer's statement of oversight
451 
452         By offering my Reviewed-by: tag, I state that:
453 
454          (a) I have carried out a technical review of this patch to
455              evaluate its appropriateness and readiness for inclusion into
456              the mainline kernel.
457 
458          (b) Any problems, concerns, or questions relating to the patch
459              have been communicated back to the submitter.  I am satisfied
460              with the submitter's response to my comments.
461 
462          (c) While there may be things that could be improved with this
463              submission, I believe that it is, at this time, (1) a
464              worthwhile modification to the kernel, and (2) free of known
465              issues which would argue against its inclusion.
466 
467          (d) While I have reviewed the patch and believe it to be sound, I
468              do not (unless explicitly stated elsewhere) make any
469              warranties or guarantees that it will achieve its stated
470              purpose or function properly in any given situation.
471 
472 A Reviewed-by tag is a statement of opinion that the patch is an
473 appropriate modification of the kernel without any remaining serious
474 technical issues.  Any interested reviewer (who has done the work) can
475 offer a Reviewed-by tag for a patch.  This tag serves to give credit to
476 reviewers and to inform maintainers of the degree of review which has been
477 done on the patch.  Reviewed-by: tags, when supplied by reviewers known to
478 understand the subject area and to perform thorough reviews, will normally
479 increase the likelihood of your patch getting into the kernel.
480 
481 A Suggested-by: tag indicates that the patch idea is suggested by the person
482 named and ensures credit to the person for the idea. Please note that this
483 tag should not be added without the reporter's permission, especially if the
484 idea was not posted in a public forum. That said, if we diligently credit our
485 idea reporters, they will, hopefully, be inspired to help us again in the
486 future.
487 
488 
489 15) The canonical patch format
490 
491 The canonical patch subject line is:
492 
493     Subject: [PATCH 001/123] subsystem: summary phrase
494 
495 The canonical patch message body contains the following:
496 
497   - A "from" line specifying the patch author.
498 
499   - An empty line.
500 
501   - The body of the explanation, which will be copied to the
502     permanent changelog to describe this patch.
503 
504   - The "Signed-off-by:" lines, described above, which will
505     also go in the changelog.
506 
507   - A marker line containing simply "---".
508 
509   - Any additional comments not suitable for the changelog.
510 
511   - The actual patch (diff output).
512 
513 The Subject line format makes it very easy to sort the emails
514 alphabetically by subject line - pretty much any email reader will
515 support that - since because the sequence number is zero-padded,
516 the numerical and alphabetic sort is the same.
517 
518 The "subsystem" in the email's Subject should identify which
519 area or subsystem of the kernel is being patched.
520 
521 The "summary phrase" in the email's Subject should concisely
522 describe the patch which that email contains.  The "summary
523 phrase" should not be a filename.  Do not use the same "summary
524 phrase" for every patch in a whole patch series (where a "patch
525 series" is an ordered sequence of multiple, related patches).
526 
527 Bear in mind that the "summary phrase" of your email becomes a
528 globally-unique identifier for that patch.  It propagates all the way
529 into the git changelog.  The "summary phrase" may later be used in
530 developer discussions which refer to the patch.  People will want to
531 google for the "summary phrase" to read discussion regarding that
532 patch.  It will also be the only thing that people may quickly see
533 when, two or three months later, they are going through perhaps
534 thousands of patches using tools such as "gitk" or "git log
535 --oneline".
536 
537 For these reasons, the "summary" must be no more than 70-75
538 characters, and it must describe both what the patch changes, as well
539 as why the patch might be necessary.  It is challenging to be both
540 succinct and descriptive, but that is what a well-written summary
541 should do.
542 
543 The "summary phrase" may be prefixed by tags enclosed in square
544 brackets: "Subject: [PATCH tag] <summary phrase>".  The tags are not
545 considered part of the summary phrase, but describe how the patch
546 should be treated.  Common tags might include a version descriptor if
547 the multiple versions of the patch have been sent out in response to
548 comments (i.e., "v1, v2, v3"), or "RFC" to indicate a request for
549 comments.  If there are four patches in a patch series the individual
550 patches may be numbered like this: 1/4, 2/4, 3/4, 4/4.  This assures
551 that developers understand the order in which the patches should be
552 applied and that they have reviewed or applied all of the patches in
553 the patch series.
554 
555 A couple of example Subjects:
556 
557     Subject: [patch 2/5] ext2: improve scalability of bitmap searching
558     Subject: [PATCHv2 001/207] x86: fix eflags tracking
559 
560 The "from" line must be the very first line in the message body,
561 and has the form:
562 
563         From: Original Author <author@example.com>
564 
565 The "from" line specifies who will be credited as the author of the
566 patch in the permanent changelog.  If the "from" line is missing,
567 then the "From:" line from the email header will be used to determine
568 the patch author in the changelog.
569 
570 The explanation body will be committed to the permanent source
571 changelog, so should make sense to a competent reader who has long
572 since forgotten the immediate details of the discussion that might
573 have led to this patch.  Including symptoms of the failure which the
574 patch addresses (kernel log messages, oops messages, etc.) is
575 especially useful for people who might be searching the commit logs
576 looking for the applicable patch.  If a patch fixes a compile failure,
577 it may not be necessary to include _all_ of the compile failures; just
578 enough that it is likely that someone searching for the patch can find
579 it.  As in the "summary phrase", it is important to be both succinct as
580 well as descriptive.
581 
582 The "---" marker line serves the essential purpose of marking for patch
583 handling tools where the changelog message ends.
584 
585 One good use for the additional comments after the "---" marker is for
586 a diffstat, to show what files have changed, and the number of
587 inserted and deleted lines per file.  A diffstat is especially useful
588 on bigger patches.  Other comments relevant only to the moment or the
589 maintainer, not suitable for the permanent changelog, should also go
590 here.  A good example of such comments might be "patch changelogs"
591 which describe what has changed between the v1 and v2 version of the
592 patch.
593 
594 If you are going to include a diffstat after the "---" marker, please
595 use diffstat options "-p 1 -w 70" so that filenames are listed from
596 the top of the kernel source tree and don't use too much horizontal
597 space (easily fit in 80 columns, maybe with some indentation).
598 
599 See more details on the proper patch format in the following
600 references.
601 
602 
603 16) Sending "git pull" requests  (from Linus emails)
604 
605 Please write the git repo address and branch name alone on the same line
606 so that I can't even by mistake pull from the wrong branch, and so
607 that a triple-click just selects the whole thing.
608 
609 So the proper format is something along the lines of:
610 
611         "Please pull from
612 
613                 git://jdelvare.pck.nerim.net/jdelvare-2.6 i2c-for-linus
614 
615          to get these changes:"
616 
617 so that I don't have to hunt-and-peck for the address and inevitably
618 get it wrong (actually, I've only gotten it wrong a few times, and
619 checking against the diffstat tells me when I get it wrong, but I'm
620 just a lot more comfortable when I don't have to "look for" the right
621 thing to pull, and double-check that I have the right branch-name).
622 
623 
624 Please use "git diff -M --stat --summary" to generate the diffstat:
625 the -M enables rename detection, and the summary enables a summary of
626 new/deleted or renamed files.
627 
628 With rename detection, the statistics are rather different [...]
629 because git will notice that a fair number of the changes are renames.
630 
631 -----------------------------------
632 SECTION 2 - HINTS, TIPS, AND TRICKS
633 -----------------------------------
634 
635 This section lists many of the common "rules" associated with code
636 submitted to the kernel.  There are always exceptions... but you must
637 have a really good reason for doing so.  You could probably call this
638 section Linus Computer Science 101.
639 
640 
641 
642 1) Read Documentation/CodingStyle
643 
644 Nuff said.  If your code deviates too much from this, it is likely
645 to be rejected without further review, and without comment.
646 
647 One significant exception is when moving code from one file to
648 another -- in this case you should not modify the moved code at all in
649 the same patch which moves it.  This clearly delineates the act of
650 moving the code and your changes.  This greatly aids review of the
651 actual differences and allows tools to better track the history of
652 the code itself.
653 
654 Check your patches with the patch style checker prior to submission
655 (scripts/checkpatch.pl).  The style checker should be viewed as
656 a guide not as the final word.  If your code looks better with
657 a violation then its probably best left alone.
658 
659 The checker reports at three levels:
660  - ERROR: things that are very likely to be wrong
661  - WARNING: things requiring careful review
662  - CHECK: things requiring thought
663 
664 You should be able to justify all violations that remain in your
665 patch.
666 
667 
668 
669 2) #ifdefs are ugly
670 
671 Code cluttered with ifdefs is difficult to read and maintain.  Don't do
672 it.  Instead, put your ifdefs in a header, and conditionally define
673 'static inline' functions, or macros, which are used in the code.
674 Let the compiler optimize away the "no-op" case.
675 
676 Simple example, of poor code:
677 
678         dev = alloc_etherdev (sizeof(struct funky_private));
679         if (!dev)
680                 return -ENODEV;
681         #ifdef CONFIG_NET_FUNKINESS
682         init_funky_net(dev);
683         #endif
684 
685 Cleaned-up example:
686 
687 (in header)
688         #ifndef CONFIG_NET_FUNKINESS
689         static inline void init_funky_net (struct net_device *d) {}
690         #endif
691 
692 (in the code itself)
693         dev = alloc_etherdev (sizeof(struct funky_private));
694         if (!dev)
695                 return -ENODEV;
696         init_funky_net(dev);
697 
698 
699 
700 3) 'static inline' is better than a macro
701 
702 Static inline functions are greatly preferred over macros.
703 They provide type safety, have no length limitations, no formatting
704 limitations, and under gcc they are as cheap as macros.
705 
706 Macros should only be used for cases where a static inline is clearly
707 suboptimal [there are a few, isolated cases of this in fast paths],
708 or where it is impossible to use a static inline function [such as
709 string-izing].
710 
711 'static inline' is preferred over 'static __inline__', 'extern inline',
712 and 'extern __inline__'.
713 
714 
715 
716 4) Don't over-design.
717 
718 Don't try to anticipate nebulous future cases which may or may not
719 be useful:  "Make it as simple as you can, and no simpler."
720 
721 
722 
723 ----------------------
724 SECTION 3 - REFERENCES
725 ----------------------
726 
727 Andrew Morton, "The perfect patch" (tpp).
728   <http://userweb.kernel.org/~akpm/stuff/tpp.txt>
729 
730 Jeff Garzik, "Linux kernel patch submission format".
731   <http://linux.yyz.us/patch-format.html>
732 
733 Greg Kroah-Hartman, "How to piss off a kernel subsystem maintainer".
734   <http://www.kroah.com/log/linux/maintainer.html>
735   <http://www.kroah.com/log/linux/maintainer-02.html>
736   <http://www.kroah.com/log/linux/maintainer-03.html>
737   <http://www.kroah.com/log/linux/maintainer-04.html>
738   <http://www.kroah.com/log/linux/maintainer-05.html>
739 
740 NO!!!! No more huge patch bombs to linux-kernel@vger.kernel.org people!
741   <http://marc.theaimsgroup.com/?l=linux-kernel&m=112112749912944&w=2>
742 
743 Kernel Documentation/CodingStyle:
744   <http://users.sosdg.org/~qiyong/lxr/source/Documentation/CodingStyle>
745 
746 Linus Torvalds's mail on the canonical patch format:
747   <http://lkml.org/lkml/2005/4/7/183>
748 
749 Andi Kleen, "On submitting kernel patches"
750   Some strategies to get difficult or controversial changes in.
751   http://halobates.de/on-submitting-patches.pdf
752 
753 --

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