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Based on kernel version 2.6.34. Page generated on 2010-05-31 16:03 EST.

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.  For earlier kernel versions, you can get it
64	from <http://www.xenotime.net/linux/doc/dontdiff>.
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
72	logical stages.  This will facilitate easier reviewing by other
73	kernel developers, very important if you want your patch accepted.
74	There are a number of scripts which can aid in this:
75	
76	Quilt:
77	http://savannah.nongnu.org/projects/quilt
78	
79	Andrew Morton's patch scripts:
80	http://userweb.kernel.org/~akpm/stuff/patch-scripts.tar.gz
81	Instead of these scripts, quilt is the recommended patch management
82	tool (see above).
83	
84	
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	
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	
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	
101	
102	
103	3) Separate your changes.
104	
105	Separate _logical changes_ into a single patch file.
106	
107	For example, if your changes include both bug fixes and performance
108	enhancements for a single driver, separate those changes into two
109	or more patches.  If your changes include an API update, and a new
110	driver which uses that new API, separate those into two patches.
111	
112	On the other hand, if you make a single change to numerous files,
113	group those changes into a single patch.  Thus a single logical change
114	is contained within a single patch.
115	
116	If one patch depends on another patch in order for a change to be
117	complete, that is OK.  Simply note "this patch depends on patch X"
118	in your patch description.
119	
120	If you cannot condense your patch set into a smaller set of patches,
121	then only post say 15 or so at a time and wait for review and integration.
122	
123	
124	
125	4) Style check your changes.
126	
127	Check your patch for basic style violations, details of which can be
128	found in Documentation/CodingStyle.  Failure to do so simply wastes
129	the reviewers time and will get your patch rejected, probably
130	without even being read.
131	
132	At a minimum you should check your patches with the patch style
133	checker prior to submission (scripts/checkpatch.pl).  You should
134	be able to justify all violations that remain in your patch.
135	
136	
137	
138	5) Select e-mail destination.
139	
140	Look through the MAINTAINERS file and the source code, and determine
141	if your change applies to a specific subsystem of the kernel, with
142	an assigned maintainer.  If so, e-mail that person.
143	
144	If no maintainer is listed, or the maintainer does not respond, send
145	your patch to the primary Linux kernel developer's mailing list,
146	linux-kernel[AT]vger.kernel.org[DOT]  Most kernel developers monitor this
147	e-mail list, and can comment on your changes.
148	
149	
150	Do not send more than 15 patches at once to the vger mailing lists!!!
151	
152	
153	Linus Torvalds is the final arbiter of all changes accepted into the
154	Linux kernel.  His e-mail address is <torvalds[AT]linux-foundation.org>[DOT] 
155	He gets a lot of e-mail, so typically you should do your best to -avoid-
156	sending him e-mail. 
157	
158	Patches which are bug fixes, are "obvious" changes, or similarly
159	require little discussion should be sent or CC'd to Linus.  Patches
160	which require discussion or do not have a clear advantage should
161	usually be sent first to linux-kernel.  Only after the patch is
162	discussed should the patch then be submitted to Linus.
163	
164	
165	
166	6) Select your CC (e-mail carbon copy) list.
167	
168	Unless you have a reason NOT to do so, CC linux-kernel[AT]vger.kernel.org[DOT]
169	
170	Other kernel developers besides Linus need to be aware of your change,
171	so that they may comment on it and offer code review and suggestions.
172	linux-kernel is the primary Linux kernel developer mailing list.
173	Other mailing lists are available for specific subsystems, such as
174	USB, framebuffer devices, the VFS, the SCSI subsystem, etc.  See the
175	MAINTAINERS file for a mailing list that relates specifically to
176	your change.
177	
178	Majordomo lists of VGER.KERNEL.ORG at:
179		<http://vger.kernel.org/vger-lists.html>
180	
181	If changes affect userland-kernel interfaces, please send
182	the MAN-PAGES maintainer (as listed in the MAINTAINERS file)
183	a man-pages patch, or at least a notification of the change,
184	so that some information makes its way into the manual pages.
185	
186	Even if the maintainer did not respond in step #5, make sure to ALWAYS
187	copy the maintainer when you change their code.
188	
189	For small patches you may want to CC the Trivial Patch Monkey
190	trivial[AT]kernel.org which collects "trivial" patches[DOT] Have a look
191	into the MAINTAINERS file for its current manager.
192	Trivial patches must qualify for one of the following rules:
193	 Spelling fixes in documentation
194	 Spelling fixes which could break grep(1)
195	 Warning fixes (cluttering with useless warnings is bad)
196	 Compilation fixes (only if they are actually correct)
197	 Runtime fixes (only if they actually fix things)
198	 Removing use of deprecated functions/macros (eg. check_region)
199	 Contact detail and documentation fixes
200	 Non-portable code replaced by portable code (even in arch-specific,
201	 since people copy, as long as it's trivial)
202	 Any fix by the author/maintainer of the file (ie. patch monkey
203	 in re-transmission mode)
204	
205	
206	
207	7) No MIME, no links, no compression, no attachments.  Just plain text.
208	
209	Linus and other kernel developers need to be able to read and comment
210	on the changes you are submitting.  It is important for a kernel
211	developer to be able to "quote" your changes, using standard e-mail
212	tools, so that they may comment on specific portions of your code.
213	
214	For this reason, all patches should be submitting e-mail "inline".
215	WARNING:  Be wary of your editor's word-wrap corrupting your patch,
216	if you choose to cut-n-paste your patch.
217	
218	Do not attach the patch as a MIME attachment, compressed or not.
219	Many popular e-mail applications will not always transmit a MIME
220	attachment as plain text, making it impossible to comment on your
221	code.  A MIME attachment also takes Linus a bit more time to process,
222	decreasing the likelihood of your MIME-attached change being accepted.
223	
224	Exception:  If your mailer is mangling patches then someone may ask
225	you to re-send them using MIME.
226	
227	See Documentation/email-clients.txt for hints about configuring
228	your e-mail client so that it sends your patches untouched.
229	
230	8) E-mail size.
231	
232	When sending patches to Linus, always follow step #7.
233	
234	Large changes are not appropriate for mailing lists, and some
235	maintainers.  If your patch, uncompressed, exceeds 300 kB in size,
236	it is preferred that you store your patch on an Internet-accessible
237	server, and provide instead a URL (link) pointing to your patch.
238	
239	
240	
241	9) Name your kernel version.
242	
243	It is important to note, either in the subject line or in the patch
244	description, the kernel version to which this patch applies.
245	
246	If the patch does not apply cleanly to the latest kernel version,
247	Linus will not apply it.
248	
249	
250	
251	10) Don't get discouraged.  Re-submit.
252	
253	After you have submitted your change, be patient and wait.  If Linus
254	likes your change and applies it, it will appear in the next version
255	of the kernel that he releases.
256	
257	However, if your change doesn't appear in the next version of the
258	kernel, there could be any number of reasons.  It's YOUR job to
259	narrow down those reasons, correct what was wrong, and submit your
260	updated change.
261	
262	It is quite common for Linus to "drop" your patch without comment.
263	That's the nature of the system.  If he drops your patch, it could be
264	due to
265	* Your patch did not apply cleanly to the latest kernel version.
266	* Your patch was not sufficiently discussed on linux-kernel.
267	* A style issue (see section 2).
268	* An e-mail formatting issue (re-read this section).
269	* A technical problem with your change.
270	* He gets tons of e-mail, and yours got lost in the shuffle.
271	* You are being annoying.
272	
273	When in doubt, solicit comments on linux-kernel mailing list.
274	
275	
276	
277	11) Include PATCH in the subject
278	
279	Due to high e-mail traffic to Linus, and to linux-kernel, it is common
280	convention to prefix your subject line with [PATCH].  This lets Linus
281	and other kernel developers more easily distinguish patches from other
282	e-mail discussions.
283	
284	
285	
286	12) Sign your work
287	
288	To improve tracking of who did what, especially with patches that can
289	percolate to their final resting place in the kernel through several
290	layers of maintainers, we've introduced a "sign-off" procedure on
291	patches that are being emailed around.
292	
293	The sign-off is a simple line at the end of the explanation for the
294	patch, which certifies that you wrote it or otherwise have the right to
295	pass it on as a open-source patch.  The rules are pretty simple: if you
296	can certify the below:
297	
298	        Developer's Certificate of Origin 1.1
299	
300	        By making a contribution to this project, I certify that:
301	
302	        (a) The contribution was created in whole or in part by me and I
303	            have the right to submit it under the open source license
304	            indicated in the file; or
305	
306	        (b) The contribution is based upon previous work that, to the best
307	            of my knowledge, is covered under an appropriate open source
308	            license and I have the right under that license to submit that
309	            work with modifications, whether created in whole or in part
310	            by me, under the same open source license (unless I am
311	            permitted to submit under a different license), as indicated
312	            in the file; or
313	
314	        (c) The contribution was provided directly to me by some other
315	            person who certified (a), (b) or (c) and I have not modified
316	            it.
317	
318		(d) I understand and agree that this project and the contribution
319		    are public and that a record of the contribution (including all
320		    personal information I submit with it, including my sign-off) is
321		    maintained indefinitely and may be redistributed consistent with
322		    this project or the open source license(s) involved.
323	
324	then you just add a line saying
325	
326		Signed-off-by: Random J Developer <random[AT]developer.example[DOT]org>
327	
328	using your real name (sorry, no pseudonyms or anonymous contributions.)
329	
330	Some people also put extra tags at the end.  They'll just be ignored for
331	now, but you can do this to mark internal company procedures or just
332	point out some special detail about the sign-off. 
333	
334	If you are a subsystem or branch maintainer, sometimes you need to slightly
335	modify patches you receive in order to merge them, because the code is not
336	exactly the same in your tree and the submitters'. If you stick strictly to
337	rule (c), you should ask the submitter to rediff, but this is a totally
338	counter-productive waste of time and energy. Rule (b) allows you to adjust
339	the code, but then it is very impolite to change one submitter's code and
340	make him endorse your bugs. To solve this problem, it is recommended that
341	you add a line between the last Signed-off-by header and yours, indicating
342	the nature of your changes. While there is nothing mandatory about this, it
343	seems like prepending the description with your mail and/or name, all
344	enclosed in square brackets, is noticeable enough to make it obvious that
345	you are responsible for last-minute changes. Example :
346	
347		Signed-off-by: Random J Developer <random[AT]developer.example[DOT]org>
348		[lucky[AT]maintainer.example.org: struct foo moved from foo.c to foo[DOT]h]
349		Signed-off-by: Lucky K Maintainer <lucky[AT]maintainer.example[DOT]org>
350	
351	This practise is particularly helpful if you maintain a stable branch and
352	want at the same time to credit the author, track changes, merge the fix,
353	and protect the submitter from complaints. Note that under no circumstances
354	can you change the author's identity (the From header), as it is the one
355	which appears in the changelog.
356	
357	Special note to back-porters: It seems to be a common and useful practise
358	to insert an indication of the origin of a patch at the top of the commit
359	message (just after the subject line) to facilitate tracking. For instance,
360	here's what we see in 2.6-stable :
361	
362	    Date:   Tue May 13 19:10:30 2008 +0000
363	
364	        SCSI: libiscsi regression in 2.6.25: fix nop timer handling
365	
366	        commit 4cf1043593db6a337f10e006c23c69e5fc93e722 upstream
367	
368	And here's what appears in 2.4 :
369	
370	    Date:   Tue May 13 22:12:27 2008 +0200
371	
372	        wireless, airo: waitbusy() won't delay
373	
374	        [backport of 2.6 commit b7acbdfbd1f277c1eb23f344f899cfa4cd0bf36a]
375	
376	Whatever the format, this information provides a valuable help to people
377	tracking your trees, and to people trying to trouble-shoot bugs in your
378	tree.
379	
380	
381	13) When to use Acked-by: and Cc:
382	
383	The Signed-off-by: tag indicates that the signer was involved in the
384	development of the patch, or that he/she was in the patch's delivery path.
385	
386	If a person was not directly involved in the preparation or handling of a
387	patch but wishes to signify and record their approval of it then they can
388	arrange to have an Acked-by: line added to the patch's changelog.
389	
390	Acked-by: is often used by the maintainer of the affected code when that
391	maintainer neither contributed to nor forwarded the patch.
392	
393	Acked-by: is not as formal as Signed-off-by:.  It is a record that the acker
394	has at least reviewed the patch and has indicated acceptance.  Hence patch
395	mergers will sometimes manually convert an acker's "yep, looks good to me"
396	into an Acked-by:.
397	
398	Acked-by: does not necessarily indicate acknowledgement of the entire patch.
399	For example, if a patch affects multiple subsystems and has an Acked-by: from
400	one subsystem maintainer then this usually indicates acknowledgement of just
401	the part which affects that maintainer's code.  Judgement should be used here.
402	When in doubt people should refer to the original discussion in the mailing
403	list archives.
404	
405	If a person has had the opportunity to comment on a patch, but has not
406	provided such comments, you may optionally add a "Cc:" tag to the patch.
407	This is the only tag which might be added without an explicit action by the
408	person it names.  This tag documents that potentially interested parties
409	have been included in the discussion
410	
411	
412	14) Using Reported-by:, Tested-by: and Reviewed-by:
413	
414	If this patch fixes a problem reported by somebody else, consider adding a
415	Reported-by: tag to credit the reporter for their contribution.  Please
416	note that this tag should not be added without the reporter's permission,
417	especially if the problem was not reported in a public forum.  That said,
418	if we diligently credit our bug reporters, they will, hopefully, be
419	inspired to help us again in the future.
420	
421	A Tested-by: tag indicates that the patch has been successfully tested (in
422	some environment) by the person named.  This tag informs maintainers that
423	some testing has been performed, provides a means to locate testers for
424	future patches, and ensures credit for the testers.
425	
426	Reviewed-by:, instead, indicates that the patch has been reviewed and found
427	acceptable according to the Reviewer's Statement:
428	
429		Reviewer's statement of oversight
430	
431		By offering my Reviewed-by: tag, I state that:
432	
433	 	 (a) I have carried out a technical review of this patch to
434		     evaluate its appropriateness and readiness for inclusion into
435		     the mainline kernel.
436	
437		 (b) Any problems, concerns, or questions relating to the patch
438		     have been communicated back to the submitter.  I am satisfied
439		     with the submitter's response to my comments.
440	
441		 (c) While there may be things that could be improved with this
442		     submission, I believe that it is, at this time, (1) a
443		     worthwhile modification to the kernel, and (2) free of known
444		     issues which would argue against its inclusion.
445	
446		 (d) While I have reviewed the patch and believe it to be sound, I
447		     do not (unless explicitly stated elsewhere) make any
448		     warranties or guarantees that it will achieve its stated
449		     purpose or function properly in any given situation.
450	
451	A Reviewed-by tag is a statement of opinion that the patch is an
452	appropriate modification of the kernel without any remaining serious
453	technical issues.  Any interested reviewer (who has done the work) can
454	offer a Reviewed-by tag for a patch.  This tag serves to give credit to
455	reviewers and to inform maintainers of the degree of review which has been
456	done on the patch.  Reviewed-by: tags, when supplied by reviewers known to
457	understand the subject area and to perform thorough reviews, will normally
458	increase the likelihood of your patch getting into the kernel.
459	
460	
461	15) The canonical patch format
462	
463	The canonical patch subject line is:
464	
465	    Subject: [PATCH 001/123] subsystem: summary phrase
466	
467	The canonical patch message body contains the following:
468	
469	  - A "from" line specifying the patch author.
470	
471	  - An empty line.
472	
473	  - The body of the explanation, which will be copied to the
474	    permanent changelog to describe this patch.
475	
476	  - The "Signed-off-by:" lines, described above, which will
477	    also go in the changelog.
478	
479	  - A marker line containing simply "---".
480	
481	  - Any additional comments not suitable for the changelog.
482	
483	  - The actual patch (diff output).
484	
485	The Subject line format makes it very easy to sort the emails
486	alphabetically by subject line - pretty much any email reader will
487	support that - since because the sequence number is zero-padded,
488	the numerical and alphabetic sort is the same.
489	
490	The "subsystem" in the email's Subject should identify which
491	area or subsystem of the kernel is being patched.
492	
493	The "summary phrase" in the email's Subject should concisely
494	describe the patch which that email contains.  The "summary
495	phrase" should not be a filename.  Do not use the same "summary
496	phrase" for every patch in a whole patch series (where a "patch
497	series" is an ordered sequence of multiple, related patches).
498	
499	Bear in mind that the "summary phrase" of your email becomes a
500	globally-unique identifier for that patch.  It propagates all the way
501	into the git changelog.  The "summary phrase" may later be used in
502	developer discussions which refer to the patch.  People will want to
503	google for the "summary phrase" to read discussion regarding that
504	patch.  It will also be the only thing that people may quickly see
505	when, two or three months later, they are going through perhaps
506	thousands of patches using tools such as "gitk" or "git log
507	--oneline".
508	
509	For these reasons, the "summary" must be no more than 70-75
510	characters, and it must describe both what the patch changes, as well
511	as why the patch might be necessary.  It is challenging to be both
512	succinct and descriptive, but that is what a well-written summary
513	should do.
514	
515	The "summary phrase" may be prefixed by tags enclosed in square
516	brackets: "Subject: [PATCH tag] <summary phrase>".  The tags are not
517	considered part of the summary phrase, but describe how the patch
518	should be treated.  Common tags might include a version descriptor if
519	the multiple versions of the patch have been sent out in response to
520	comments (i.e., "v1, v2, v3"), or "RFC" to indicate a request for
521	comments.  If there are four patches in a patch series the individual
522	patches may be numbered like this: 1/4, 2/4, 3/4, 4/4.  This assures
523	that developers understand the order in which the patches should be
524	applied and that they have reviewed or applied all of the patches in
525	the patch series.
526	
527	A couple of example Subjects:
528	
529	    Subject: [patch 2/5] ext2: improve scalability of bitmap searching
530	    Subject: [PATCHv2 001/207] x86: fix eflags tracking
531	
532	The "from" line must be the very first line in the message body,
533	and has the form:
534	
535	        From: Original Author <author[AT]example[DOT]com>
536	
537	The "from" line specifies who will be credited as the author of the
538	patch in the permanent changelog.  If the "from" line is missing,
539	then the "From:" line from the email header will be used to determine
540	the patch author in the changelog.
541	
542	The explanation body will be committed to the permanent source
543	changelog, so should make sense to a competent reader who has long
544	since forgotten the immediate details of the discussion that might
545	have led to this patch.  Including symptoms of the failure which the
546	patch addresses (kernel log messages, oops messages, etc.) is
547	especially useful for people who might be searching the commit logs
548	looking for the applicable patch.  If a patch fixes a compile failure,
549	it may not be necessary to include _all_ of the compile failures; just
550	enough that it is likely that someone searching for the patch can find
551	it.  As in the "summary phrase", it is important to be both succinct as
552	well as descriptive.
553	
554	The "---" marker line serves the essential purpose of marking for patch
555	handling tools where the changelog message ends.
556	
557	One good use for the additional comments after the "---" marker is for
558	a diffstat, to show what files have changed, and the number of
559	inserted and deleted lines per file.  A diffstat is especially useful
560	on bigger patches.  Other comments relevant only to the moment or the
561	maintainer, not suitable for the permanent changelog, should also go
562	here.  A good example of such comments might be "patch changelogs"
563	which describe what has changed between the v1 and v2 version of the
564	patch.
565	
566	If you are going to include a diffstat after the "---" marker, please
567	use diffstat options "-p 1 -w 70" so that filenames are listed from
568	the top of the kernel source tree and don't use too much horizontal
569	space (easily fit in 80 columns, maybe with some indentation).
570	
571	See more details on the proper patch format in the following
572	references.
573	
574	
575	16) Sending "git pull" requests  (from Linus emails)
576	
577	Please write the git repo address and branch name alone on the same line
578	so that I can't even by mistake pull from the wrong branch, and so
579	that a triple-click just selects the whole thing.
580	
581	So the proper format is something along the lines of:
582	
583		"Please pull from
584	
585			git://jdelvare.pck.nerim.net/jdelvare-2.6 i2c-for-linus
586	
587		 to get these changes:"
588	
589	so that I don't have to hunt-and-peck for the address and inevitably
590	get it wrong (actually, I've only gotten it wrong a few times, and
591	checking against the diffstat tells me when I get it wrong, but I'm
592	just a lot more comfortable when I don't have to "look for" the right
593	thing to pull, and double-check that I have the right branch-name).
594	
595	
596	Please use "git diff -M --stat --summary" to generate the diffstat:
597	the -M enables rename detection, and the summary enables a summary of
598	new/deleted or renamed files.
599	
600	With rename detection, the statistics are rather different [...]
601	because git will notice that a fair number of the changes are renames.
602	
603	-----------------------------------
604	SECTION 2 - HINTS, TIPS, AND TRICKS
605	-----------------------------------
606	
607	This section lists many of the common "rules" associated with code
608	submitted to the kernel.  There are always exceptions... but you must
609	have a really good reason for doing so.  You could probably call this
610	section Linus Computer Science 101.
611	
612	
613	
614	1) Read Documentation/CodingStyle
615	
616	Nuff said.  If your code deviates too much from this, it is likely
617	to be rejected without further review, and without comment.
618	
619	One significant exception is when moving code from one file to
620	another -- in this case you should not modify the moved code at all in
621	the same patch which moves it.  This clearly delineates the act of
622	moving the code and your changes.  This greatly aids review of the
623	actual differences and allows tools to better track the history of
624	the code itself.
625	
626	Check your patches with the patch style checker prior to submission
627	(scripts/checkpatch.pl).  The style checker should be viewed as
628	a guide not as the final word.  If your code looks better with
629	a violation then its probably best left alone.
630	
631	The checker reports at three levels:
632	 - ERROR: things that are very likely to be wrong
633	 - WARNING: things requiring careful review
634	 - CHECK: things requiring thought
635	
636	You should be able to justify all violations that remain in your
637	patch.
638	
639	
640	
641	2) #ifdefs are ugly
642	
643	Code cluttered with ifdefs is difficult to read and maintain.  Don't do
644	it.  Instead, put your ifdefs in a header, and conditionally define
645	'static inline' functions, or macros, which are used in the code.
646	Let the compiler optimize away the "no-op" case.
647	
648	Simple example, of poor code:
649	
650		dev = alloc_etherdev (sizeof(struct funky_private));
651		if (!dev)
652			return -ENODEV;
653		#ifdef CONFIG_NET_FUNKINESS
654		init_funky_net(dev);
655		#endif
656	
657	Cleaned-up example:
658	
659	(in header)
660		#ifndef CONFIG_NET_FUNKINESS
661		static inline void init_funky_net (struct net_device *d) {}
662		#endif
663	
664	(in the code itself)
665		dev = alloc_etherdev (sizeof(struct funky_private));
666		if (!dev)
667			return -ENODEV;
668		init_funky_net(dev);
669	
670	
671	
672	3) 'static inline' is better than a macro
673	
674	Static inline functions are greatly preferred over macros.
675	They provide type safety, have no length limitations, no formatting
676	limitations, and under gcc they are as cheap as macros.
677	
678	Macros should only be used for cases where a static inline is clearly
679	suboptimal [there are a few, isolated cases of this in fast paths],
680	or where it is impossible to use a static inline function [such as
681	string-izing].
682	
683	'static inline' is preferred over 'static __inline__', 'extern inline',
684	and 'extern __inline__'.
685	
686	
687	
688	4) Don't over-design.
689	
690	Don't try to anticipate nebulous future cases which may or may not
691	be useful:  "Make it as simple as you can, and no simpler."
692	
693	
694	
695	----------------------
696	SECTION 3 - REFERENCES
697	----------------------
698	
699	Andrew Morton, "The perfect patch" (tpp).
700	  <http://userweb.kernel.org/~akpm/stuff/tpp.txt>
701	
702	Jeff Garzik, "Linux kernel patch submission format".
703	  <http://linux.yyz.us/patch-format.html>
704	
705	Greg Kroah-Hartman, "How to piss off a kernel subsystem maintainer".
706	  <http://www.kroah.com/log/2005/03/31/>
707	  <http://www.kroah.com/log/2005/07/08/>
708	  <http://www.kroah.com/log/2005/10/19/>
709	  <http://www.kroah.com/log/2006/01/11/>
710	
711	NO!!!! No more huge patch bombs to linux-kernel[AT]vger.kernel[DOT]org people!
712	  <http://marc.theaimsgroup.com/?l=linux-kernel&m=112112749912944&w=2>
713	
714	Kernel Documentation/CodingStyle:
715	  <http://users.sosdg.org/~qiyong/lxr/source/Documentation/CodingStyle>
716	
717	Linus Torvalds's mail on the canonical patch format:
718	  <http://lkml.org/lkml/2005/4/7/183>
719	
720	Andi Kleen, "On submitting kernel patches"
721	  Some strategies to get difficult or controversal changes in.
722	  http://halobates.de/on-submitting-patches.pdf
723	
724	--
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