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Based on kernel version 2.6.30. Page generated on 2009-06-11 10:12 EST.

1	HOWTO do Linux kernel development
2	---------------------------------
3	
4	This is the be-all, end-all document on this topic.  It contains
5	instructions on how to become a Linux kernel developer and how to learn
6	to work with the Linux kernel development community.  It tries to not
7	contain anything related to the technical aspects of kernel programming,
8	but will help point you in the right direction for that.
9	
10	If anything in this document becomes out of date, please send in patches
11	to the maintainer of this file, who is listed at the bottom of the
12	document.
13	
14	
15	Introduction
16	------------
17	
18	So, you want to learn how to become a Linux kernel developer?  Or you
19	have been told by your manager, "Go write a Linux driver for this
20	device."  This document's goal is to teach you everything you need to
21	know to achieve this by describing the process you need to go through,
22	and hints on how to work with the community.  It will also try to
23	explain some of the reasons why the community works like it does.
24	
25	The kernel is written mostly in C, with some architecture-dependent
26	parts written in assembly. A good understanding of C is required for
27	kernel development.  Assembly (any architecture) is not required unless
28	you plan to do low-level development for that architecture.  Though they
29	are not a good substitute for a solid C education and/or years of
30	experience, the following books are good for, if anything, reference:
31	 - "The C Programming Language" by Kernighan and Ritchie [Prentice Hall]
32	 - "Practical C Programming" by Steve Oualline [O'Reilly]
33	 - "C:  A Reference Manual" by Harbison and Steele [Prentice Hall]
34	
35	The kernel is written using GNU C and the GNU toolchain.  While it
36	adheres to the ISO C89 standard, it uses a number of extensions that are
37	not featured in the standard.  The kernel is a freestanding C
38	environment, with no reliance on the standard C library, so some
39	portions of the C standard are not supported.  Arbitrary long long
40	divisions and floating point are not allowed.  It can sometimes be
41	difficult to understand the assumptions the kernel has on the toolchain
42	and the extensions that it uses, and unfortunately there is no
43	definitive reference for them.  Please check the gcc info pages (`info
44	gcc`) for some information on them.
45	
46	Please remember that you are trying to learn how to work with the
47	existing development community.  It is a diverse group of people, with
48	high standards for coding, style and procedure.  These standards have
49	been created over time based on what they have found to work best for
50	such a large and geographically dispersed team.  Try to learn as much as
51	possible about these standards ahead of time, as they are well
52	documented; do not expect people to adapt to you or your company's way
53	of doing things.
54	
55	
56	Legal Issues
57	------------
58	
59	The Linux kernel source code is released under the GPL.  Please see the
60	file, COPYING, in the main directory of the source tree, for details on
61	the license.  If you have further questions about the license, please
62	contact a lawyer, and do not ask on the Linux kernel mailing list.  The
63	people on the mailing lists are not lawyers, and you should not rely on
64	their statements on legal matters.
65	
66	For common questions and answers about the GPL, please see:
67		http://www.gnu.org/licenses/gpl-faq.html
68	
69	
70	Documentation
71	------------
72	
73	The Linux kernel source tree has a large range of documents that are
74	invaluable for learning how to interact with the kernel community.  When
75	new features are added to the kernel, it is recommended that new
76	documentation files are also added which explain how to use the feature.
77	When a kernel change causes the interface that the kernel exposes to
78	userspace to change, it is recommended that you send the information or
79	a patch to the manual pages explaining the change to the manual pages
80	maintainer at mtk.manpages[AT]gmail[DOT]com, and CC the list
81	linux-api[AT]vger.kernel.org[DOT]
82	
83	Here is a list of files that are in the kernel source tree that are
84	required reading:
85	  README
86	    This file gives a short background on the Linux kernel and describes
87	    what is necessary to do to configure and build the kernel.  People
88	    who are new to the kernel should start here.
89	
90	  Documentation/Changes
91	    This file gives a list of the minimum levels of various software
92	    packages that are necessary to build and run the kernel
93	    successfully.
94	
95	  Documentation/CodingStyle
96	    This describes the Linux kernel coding style, and some of the
97	    rationale behind it. All new code is expected to follow the
98	    guidelines in this document. Most maintainers will only accept
99	    patches if these rules are followed, and many people will only
100	    review code if it is in the proper style.
101	
102	  Documentation/SubmittingPatches
103	  Documentation/SubmittingDrivers
104	    These files describe in explicit detail how to successfully create
105	    and send a patch, including (but not limited to):
106	       - Email contents
107	       - Email format
108	       - Who to send it to
109	    Following these rules will not guarantee success (as all patches are
110	    subject to scrutiny for content and style), but not following them
111	    will almost always prevent it.
112	
113	    Other excellent descriptions of how to create patches properly are:
114		"The Perfect Patch"
115			http://userweb.kernel.org/~akpm/stuff/tpp.txt
116		"Linux kernel patch submission format"
117			http://linux.yyz.us/patch-format.html
118	
119	  Documentation/stable_api_nonsense.txt
120	    This file describes the rationale behind the conscious decision to
121	    not have a stable API within the kernel, including things like:
122	      - Subsystem shim-layers (for compatibility?)
123	      - Driver portability between Operating Systems.
124	      - Mitigating rapid change within the kernel source tree (or
125		preventing rapid change)
126	    This document is crucial for understanding the Linux development
127	    philosophy and is very important for people moving to Linux from
128	    development on other Operating Systems.
129	
130	  Documentation/SecurityBugs
131	    If you feel you have found a security problem in the Linux kernel,
132	    please follow the steps in this document to help notify the kernel
133	    developers, and help solve the issue.
134	
135	  Documentation/ManagementStyle
136	    This document describes how Linux kernel maintainers operate and the
137	    shared ethos behind their methodologies.  This is important reading
138	    for anyone new to kernel development (or anyone simply curious about
139	    it), as it resolves a lot of common misconceptions and confusion
140	    about the unique behavior of kernel maintainers.
141	
142	  Documentation/stable_kernel_rules.txt
143	    This file describes the rules on how the stable kernel releases
144	    happen, and what to do if you want to get a change into one of these
145	    releases.
146	
147	  Documentation/kernel-docs.txt
148	    A list of external documentation that pertains to kernel
149	    development.  Please consult this list if you do not find what you
150	    are looking for within the in-kernel documentation.
151	
152	  Documentation/applying-patches.txt
153	    A good introduction describing exactly what a patch is and how to
154	    apply it to the different development branches of the kernel.
155	
156	The kernel also has a large number of documents that can be
157	automatically generated from the source code itself.  This includes a
158	full description of the in-kernel API, and rules on how to handle
159	locking properly.  The documents will be created in the
160	Documentation/DocBook/ directory and can be generated as PDF,
161	Postscript, HTML, and man pages by running:
162		make pdfdocs
163		make psdocs
164		make htmldocs
165		make mandocs
166	respectively from the main kernel source directory.
167	
168	
169	Becoming A Kernel Developer
170	---------------------------
171	
172	If you do not know anything about Linux kernel development, you should
173	look at the Linux KernelNewbies project:
174		http://kernelnewbies.org
175	It consists of a helpful mailing list where you can ask almost any type
176	of basic kernel development question (make sure to search the archives
177	first, before asking something that has already been answered in the
178	past.)  It also has an IRC channel that you can use to ask questions in
179	real-time, and a lot of helpful documentation that is useful for
180	learning about Linux kernel development.
181	
182	The website has basic information about code organization, subsystems,
183	and current projects (both in-tree and out-of-tree). It also describes
184	some basic logistical information, like how to compile a kernel and
185	apply a patch.
186	
187	If you do not know where you want to start, but you want to look for
188	some task to start doing to join into the kernel development community,
189	go to the Linux Kernel Janitor's project:
190		http://janitor.kernelnewbies.org/
191	It is a great place to start.  It describes a list of relatively simple
192	problems that need to be cleaned up and fixed within the Linux kernel
193	source tree.  Working with the developers in charge of this project, you
194	will learn the basics of getting your patch into the Linux kernel tree,
195	and possibly be pointed in the direction of what to go work on next, if
196	you do not already have an idea.
197	
198	If you already have a chunk of code that you want to put into the kernel
199	tree, but need some help getting it in the proper form, the
200	kernel-mentors project was created to help you out with this.  It is a
201	mailing list, and can be found at:
202		http://selenic.com/mailman/listinfo/kernel-mentors
203	
204	Before making any actual modifications to the Linux kernel code, it is
205	imperative to understand how the code in question works.  For this
206	purpose, nothing is better than reading through it directly (most tricky
207	bits are commented well), perhaps even with the help of specialized
208	tools.  One such tool that is particularly recommended is the Linux
209	Cross-Reference project, which is able to present source code in a
210	self-referential, indexed webpage format. An excellent up-to-date
211	repository of the kernel code may be found at:
212		http://users.sosdg.org/~qiyong/lxr/
213	
214	
215	The development process
216	-----------------------
217	
218	Linux kernel development process currently consists of a few different
219	main kernel "branches" and lots of different subsystem-specific kernel
220	branches.  These different branches are:
221	  - main 2.6.x kernel tree
222	  - 2.6.x.y -stable kernel tree
223	  - 2.6.x -git kernel patches
224	  - 2.6.x -mm kernel patches
225	  - subsystem specific kernel trees and patches
226	
227	2.6.x kernel tree
228	-----------------
229	2.6.x kernels are maintained by Linus Torvalds, and can be found on
230	kernel.org in the pub/linux/kernel/v2.6/ directory.  Its development
231	process is as follows:
232	  - As soon as a new kernel is released a two weeks window is open,
233	    during this period of time maintainers can submit big diffs to
234	    Linus, usually the patches that have already been included in the
235	    -mm kernel for a few weeks.  The preferred way to submit big changes
236	    is using git (the kernel's source management tool, more information
237	    can be found at http://git.or.cz/) but plain patches are also just
238	    fine.
239	  - After two weeks a -rc1 kernel is released it is now possible to push
240	    only patches that do not include new features that could affect the
241	    stability of the whole kernel.  Please note that a whole new driver
242	    (or filesystem) might be accepted after -rc1 because there is no
243	    risk of causing regressions with such a change as long as the change
244	    is self-contained and does not affect areas outside of the code that
245	    is being added.  git can be used to send patches to Linus after -rc1
246	    is released, but the patches need to also be sent to a public
247	    mailing list for review.
248	  - A new -rc is released whenever Linus deems the current git tree to
249	    be in a reasonably sane state adequate for testing.  The goal is to
250	    release a new -rc kernel every week.
251	  - Process continues until the kernel is considered "ready", the
252	    process should last around 6 weeks.
253	  - Known regressions in each release are periodically posted to the 
254	    linux-kernel mailing list.  The goal is to reduce the length of 
255	    that list to zero before declaring the kernel to be "ready," but, in
256	    the real world, a small number of regressions often remain at 
257	    release time.
258	
259	It is worth mentioning what Andrew Morton wrote on the linux-kernel
260	mailing list about kernel releases:
261		"Nobody knows when a kernel will be released, because it's
262		released according to perceived bug status, not according to a
263		preconceived timeline."
264	
265	2.6.x.y -stable kernel tree
266	---------------------------
267	Kernels with 4-part versions are -stable kernels. They contain
268	relatively small and critical fixes for security problems or significant
269	regressions discovered in a given 2.6.x kernel.
270	
271	This is the recommended branch for users who want the most recent stable
272	kernel and are not interested in helping test development/experimental
273	versions.
274	
275	If no 2.6.x.y kernel is available, then the highest numbered 2.6.x
276	kernel is the current stable kernel.
277	
278	2.6.x.y are maintained by the "stable" team <stable[AT]kernel[DOT]org>, and are
279	released as needs dictate.  The normal release period is approximately 
280	two weeks, but it can be longer if there are no pressing problems.  A
281	security-related problem, instead, can cause a release to happen almost
282	instantly.
283	
284	The file Documentation/stable_kernel_rules.txt in the kernel tree
285	documents what kinds of changes are acceptable for the -stable tree, and
286	how the release process works.
287	
288	2.6.x -git patches
289	------------------
290	These are daily snapshots of Linus' kernel tree which are managed in a
291	git repository (hence the name.) These patches are usually released
292	daily and represent the current state of Linus' tree.  They are more
293	experimental than -rc kernels since they are generated automatically
294	without even a cursory glance to see if they are sane.
295	
296	2.6.x -mm kernel patches
297	------------------------
298	These are experimental kernel patches released by Andrew Morton.  Andrew
299	takes all of the different subsystem kernel trees and patches and mushes
300	them together, along with a lot of patches that have been plucked from
301	the linux-kernel mailing list.  This tree serves as a proving ground for
302	new features and patches.  Once a patch has proved its worth in -mm for
303	a while Andrew or the subsystem maintainer pushes it on to Linus for
304	inclusion in mainline.
305	
306	It is heavily encouraged that all new patches get tested in the -mm tree
307	before they are sent to Linus for inclusion in the main kernel tree.  Code
308	which does not make an appearance in -mm before the opening of the merge
309	window will prove hard to merge into the mainline.
310	
311	These kernels are not appropriate for use on systems that are supposed
312	to be stable and they are more risky to run than any of the other
313	branches.
314	
315	If you wish to help out with the kernel development process, please test
316	and use these kernel releases and provide feedback to the linux-kernel
317	mailing list if you have any problems, and if everything works properly.
318	
319	In addition to all the other experimental patches, these kernels usually
320	also contain any changes in the mainline -git kernels available at the
321	time of release.
322	
323	The -mm kernels are not released on a fixed schedule, but usually a few
324	-mm kernels are released in between each -rc kernel (1 to 3 is common).
325	
326	Subsystem Specific kernel trees and patches
327	-------------------------------------------
328	A number of the different kernel subsystem developers expose their
329	development trees so that others can see what is happening in the
330	different areas of the kernel.  These trees are pulled into the -mm
331	kernel releases as described above.
332	
333	Here is a list of some of the different kernel trees available:
334	  git trees:
335	    - Kbuild development tree, Sam Ravnborg <sam[AT]ravnborg[DOT]org>
336		git.kernel.org:/pub/scm/linux/kernel/git/sam/kbuild.git
337	
338	    - ACPI development tree, Len Brown <len.brown[AT]intel[DOT]com>
339		git.kernel.org:/pub/scm/linux/kernel/git/lenb/linux-acpi-2.6.git
340	
341	    - Block development tree, Jens Axboe <jens.axboe[AT]oracle[DOT]com>
342		git.kernel.org:/pub/scm/linux/kernel/git/axboe/linux-2.6-block.git
343	
344	    - DRM development tree, Dave Airlie <airlied[AT]linux[DOT]ie>
345		git.kernel.org:/pub/scm/linux/kernel/git/airlied/drm-2.6.git
346	
347	    - ia64 development tree, Tony Luck <tony.luck[AT]intel[DOT]com>
348		git.kernel.org:/pub/scm/linux/kernel/git/aegl/linux-2.6.git
349	
350	    - infiniband, Roland Dreier <rolandd[AT]cisco[DOT]com>
351		git.kernel.org:/pub/scm/linux/kernel/git/roland/infiniband.git
352	
353	    - libata, Jeff Garzik <jgarzik[AT]pobox[DOT]com>
354		git.kernel.org:/pub/scm/linux/kernel/git/jgarzik/libata-dev.git
355	
356	    - network drivers, Jeff Garzik <jgarzik[AT]pobox[DOT]com>
357		git.kernel.org:/pub/scm/linux/kernel/git/jgarzik/netdev-2.6.git
358	
359	    - pcmcia, Dominik Brodowski <linux[AT]dominikbrodowski[DOT]net>
360		git.kernel.org:/pub/scm/linux/kernel/git/brodo/pcmcia-2.6.git
361	
362	    - SCSI, James Bottomley <James.Bottomley[AT]hansenpartnership[DOT]com>
363		git.kernel.org:/pub/scm/linux/kernel/git/jejb/scsi-misc-2.6.git
364	
365	    - x86, Ingo Molnar <mingo[AT]elte[DOT]hu>
366		git://git.kernel.org/pub/scm/linux/kernel/git/x86/linux-2.6-x86.git
367	
368	  quilt trees:
369	    - USB, Driver Core, and I2C, Greg Kroah-Hartman <gregkh[AT]suse[DOT]de>
370		kernel.org/pub/linux/kernel/people/gregkh/gregkh-2.6/
371	
372	  Other kernel trees can be found listed at http://git.kernel.org/ and in
373	  the MAINTAINERS file.
374	
375	Bug Reporting
376	-------------
377	
378	bugzilla.kernel.org is where the Linux kernel developers track kernel
379	bugs.  Users are encouraged to report all bugs that they find in this
380	tool.  For details on how to use the kernel bugzilla, please see:
381		http://bugzilla.kernel.org/page.cgi?id=faq.html
382	
383	The file REPORTING-BUGS in the main kernel source directory has a good
384	template for how to report a possible kernel bug, and details what kind
385	of information is needed by the kernel developers to help track down the
386	problem.
387	
388	
389	Managing bug reports
390	--------------------
391	
392	One of the best ways to put into practice your hacking skills is by fixing
393	bugs reported by other people. Not only you will help to make the kernel
394	more stable, you'll learn to fix real world problems and you will improve
395	your skills, and other developers will be aware of your presence. Fixing
396	bugs is one of the best ways to get merits among other developers, because
397	not many people like wasting time fixing other people's bugs.
398	
399	To work in the already reported bug reports, go to http://bugzilla.kernel.org.
400	If you want to be advised of the future bug reports, you can subscribe to the
401	bugme-new mailing list (only new bug reports are mailed here) or to the
402	bugme-janitor mailing list (every change in the bugzilla is mailed here)
403	
404		http://lists.linux-foundation.org/mailman/listinfo/bugme-new
405		http://lists.linux-foundation.org/mailman/listinfo/bugme-janitors
406	
407	
408	
409	Mailing lists
410	-------------
411	
412	As some of the above documents describe, the majority of the core kernel
413	developers participate on the Linux Kernel Mailing list.  Details on how
414	to subscribe and unsubscribe from the list can be found at:
415		http://vger.kernel.org/vger-lists.html#linux-kernel
416	There are archives of the mailing list on the web in many different
417	places.  Use a search engine to find these archives.  For example:
418		http://dir.gmane.org/gmane.linux.kernel
419	It is highly recommended that you search the archives about the topic
420	you want to bring up, before you post it to the list. A lot of things
421	already discussed in detail are only recorded at the mailing list
422	archives.
423	
424	Most of the individual kernel subsystems also have their own separate
425	mailing list where they do their development efforts.  See the
426	MAINTAINERS file for a list of what these lists are for the different
427	groups.
428	
429	Many of the lists are hosted on kernel.org. Information on them can be
430	found at:
431		http://vger.kernel.org/vger-lists.html
432	
433	Please remember to follow good behavioral habits when using the lists.
434	Though a bit cheesy, the following URL has some simple guidelines for
435	interacting with the list (or any list):
436		http://www.albion.com/netiquette/
437	
438	If multiple people respond to your mail, the CC: list of recipients may
439	get pretty large. Don't remove anybody from the CC: list without a good
440	reason, or don't reply only to the list address. Get used to receiving the
441	mail twice, one from the sender and the one from the list, and don't try
442	to tune that by adding fancy mail-headers, people will not like it.
443	
444	Remember to keep the context and the attribution of your replies intact,
445	keep the "John Kernelhacker wrote ...:" lines at the top of your reply, and
446	add your statements between the individual quoted sections instead of
447	writing at the top of the mail.
448	
449	If you add patches to your mail, make sure they are plain readable text
450	as stated in Documentation/SubmittingPatches. Kernel developers don't
451	want to deal with attachments or compressed patches; they may want
452	to comment on individual lines of your patch, which works only that way.
453	Make sure you use a mail program that does not mangle spaces and tab
454	characters. A good first test is to send the mail to yourself and try
455	to apply your own patch by yourself. If that doesn't work, get your
456	mail program fixed or change it until it works.
457	
458	Above all, please remember to show respect to other subscribers.
459	
460	
461	Working with the community
462	--------------------------
463	
464	The goal of the kernel community is to provide the best possible kernel
465	there is.  When you submit a patch for acceptance, it will be reviewed
466	on its technical merits and those alone.  So, what should you be
467	expecting?
468	  - criticism
469	  - comments
470	  - requests for change
471	  - requests for justification
472	  - silence
473	
474	Remember, this is part of getting your patch into the kernel.  You have
475	to be able to take criticism and comments about your patches, evaluate
476	them at a technical level and either rework your patches or provide
477	clear and concise reasoning as to why those changes should not be made.
478	If there are no responses to your posting, wait a few days and try
479	again, sometimes things get lost in the huge volume.
480	
481	What should you not do?
482	  - expect your patch to be accepted without question
483	  - become defensive
484	  - ignore comments
485	  - resubmit the patch without making any of the requested changes
486	
487	In a community that is looking for the best technical solution possible,
488	there will always be differing opinions on how beneficial a patch is.
489	You have to be cooperative, and willing to adapt your idea to fit within
490	the kernel.  Or at least be willing to prove your idea is worth it.
491	Remember, being wrong is acceptable as long as you are willing to work
492	toward a solution that is right.
493	
494	It is normal that the answers to your first patch might simply be a list
495	of a dozen things you should correct.  This does _not_ imply that your
496	patch will not be accepted, and it is _not_ meant against you
497	personally.  Simply correct all issues raised against your patch and
498	resend it.
499	
500	
501	Differences between the kernel community and corporate structures
502	-----------------------------------------------------------------
503	
504	The kernel community works differently than most traditional corporate
505	development environments.  Here are a list of things that you can try to
506	do to try to avoid problems:
507	  Good things to say regarding your proposed changes:
508	    - "This solves multiple problems."
509	    - "This deletes 2000 lines of code."
510	    - "Here is a patch that explains what I am trying to describe."
511	    - "I tested it on 5 different architectures..."
512	    - "Here is a series of small patches that..."
513	    - "This increases performance on typical machines..."
514	
515	  Bad things you should avoid saying:
516	    - "We did it this way in AIX/ptx/Solaris, so therefore it must be
517	      good..."
518	    - "I've being doing this for 20 years, so..."
519	    - "This is required for my company to make money"
520	    - "This is for our Enterprise product line."
521	    - "Here is my 1000 page design document that describes my idea"
522	    - "I've been working on this for 6 months..."
523	    - "Here's a 5000 line patch that..."
524	    - "I rewrote all of the current mess, and here it is..."
525	    - "I have a deadline, and this patch needs to be applied now."
526	
527	Another way the kernel community is different than most traditional
528	software engineering work environments is the faceless nature of
529	interaction.  One benefit of using email and irc as the primary forms of
530	communication is the lack of discrimination based on gender or race.
531	The Linux kernel work environment is accepting of women and minorities
532	because all you are is an email address.  The international aspect also
533	helps to level the playing field because you can't guess gender based on
534	a person's name. A man may be named Andrea and a woman may be named Pat.
535	Most women who have worked in the Linux kernel and have expressed an
536	opinion have had positive experiences.
537	
538	The language barrier can cause problems for some people who are not
539	comfortable with English.  A good grasp of the language can be needed in
540	order to get ideas across properly on mailing lists, so it is
541	recommended that you check your emails to make sure they make sense in
542	English before sending them.
543	
544	
545	Break up your changes
546	---------------------
547	
548	The Linux kernel community does not gladly accept large chunks of code
549	dropped on it all at once.  The changes need to be properly introduced,
550	discussed, and broken up into tiny, individual portions.  This is almost
551	the exact opposite of what companies are used to doing.  Your proposal
552	should also be introduced very early in the development process, so that
553	you can receive feedback on what you are doing.  It also lets the
554	community feel that you are working with them, and not simply using them
555	as a dumping ground for your feature.  However, don't send 50 emails at
556	one time to a mailing list, your patch series should be smaller than
557	that almost all of the time.
558	
559	The reasons for breaking things up are the following:
560	
561	1) Small patches increase the likelihood that your patches will be
562	   applied, since they don't take much time or effort to verify for
563	   correctness.  A 5 line patch can be applied by a maintainer with
564	   barely a second glance. However, a 500 line patch may take hours to
565	   review for correctness (the time it takes is exponentially
566	   proportional to the size of the patch, or something).
567	
568	   Small patches also make it very easy to debug when something goes
569	   wrong.  It's much easier to back out patches one by one than it is
570	   to dissect a very large patch after it's been applied (and broken
571	   something).
572	
573	2) It's important not only to send small patches, but also to rewrite
574	   and simplify (or simply re-order) patches before submitting them.
575	
576	Here is an analogy from kernel developer Al Viro:
577		"Think of a teacher grading homework from a math student.  The
578		teacher does not want to see the student's trials and errors
579		before they came up with the solution. They want to see the
580		cleanest, most elegant answer.  A good student knows this, and
581		would never submit her intermediate work before the final
582		solution."
583	
584		The same is true of kernel development. The maintainers and
585		reviewers do not want to see the thought process behind the
586		solution to the problem one is solving. They want to see a
587		simple and elegant solution."
588	
589	It may be challenging to keep the balance between presenting an elegant
590	solution and working together with the community and discussing your
591	unfinished work. Therefore it is good to get early in the process to
592	get feedback to improve your work, but also keep your changes in small
593	chunks that they may get already accepted, even when your whole task is
594	not ready for inclusion now.
595	
596	Also realize that it is not acceptable to send patches for inclusion
597	that are unfinished and will be "fixed up later."
598	
599	
600	Justify your change
601	-------------------
602	
603	Along with breaking up your patches, it is very important for you to let
604	the Linux community know why they should add this change.  New features
605	must be justified as being needed and useful.
606	
607	
608	Document your change
609	--------------------
610	
611	When sending in your patches, pay special attention to what you say in
612	the text in your email.  This information will become the ChangeLog
613	information for the patch, and will be preserved for everyone to see for
614	all time.  It should describe the patch completely, containing:
615	  - why the change is necessary
616	  - the overall design approach in the patch
617	  - implementation details
618	  - testing results
619	
620	For more details on what this should all look like, please see the
621	ChangeLog section of the document:
622	  "The Perfect Patch"
623	      http://userweb.kernel.org/~akpm/stuff/tpp.txt
624	
625	
626	
627	
628	All of these things are sometimes very hard to do. It can take years to
629	perfect these practices (if at all). It's a continuous process of
630	improvement that requires a lot of patience and determination. But
631	don't give up, it's possible. Many have done it before, and each had to
632	start exactly where you are now.
633	
634	
635	
636	
637	----------
638	Thanks to Paolo Ciarrocchi who allowed the "Development Process"
639	(http://linux.tar.bz/articles/2.6-development_process) section
640	to be based on text he had written, and to Randy Dunlap and Gerrit
641	Huizenga for some of the list of things you should and should not say.
642	Also thanks to Pat Mochel, Hanna Linder, Randy Dunlap, Kay Sievers,
643	Vojtech Pavlik, Jan Kara, Josh Boyer, Kees Cook, Andrew Morton, Andi
644	Kleen, Vadim Lobanov, Jesper Juhl, Adrian Bunk, Keri Harris, Frans Pop,
645	David A. Wheeler, Junio Hamano, Michael Kerrisk, and Alex Shepard for
646	their review, comments, and contributions.  Without their help, this
647	document would not have been possible.
648	
649	
650	
651	Maintainer: Greg Kroah-Hartman <greg[AT]kroah[DOT]com>
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