Contents of /alx-src/tags/kernel26-2.6.12-alx-r9/Documentation/SubmittingPatches
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Wed Mar 4 11:03:09 2009 UTC (15 years, 2 months ago) by niro
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Tag kernel26-2.6.12-alx-r9
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 | If you are submitting a driver, also read Documentation/SubmittingDrivers. |
14 | |
15 | |
16 | |
17 | -------------------------------------------- |
18 | SECTION 1 - CREATING AND SENDING YOUR CHANGE |
19 | -------------------------------------------- |
20 | |
21 | |
22 | |
23 | 1) "diff -up" |
24 | ------------ |
25 | |
26 | Use "diff -up" or "diff -uprN" to create patches. |
27 | |
28 | All changes to the Linux kernel occur in the form of patches, as |
29 | generated by diff(1). When creating your patch, make sure to create it |
30 | in "unified diff" format, as supplied by the '-u' argument to diff(1). |
31 | Also, please use the '-p' argument which shows which C function each |
32 | change is in - that makes the resultant diff a lot easier to read. |
33 | Patches should be based in the root kernel source directory, |
34 | not in any lower subdirectory. |
35 | |
36 | To create a patch for a single file, it is often sufficient to do: |
37 | |
38 | SRCTREE= linux-2.4 |
39 | MYFILE= drivers/net/mydriver.c |
40 | |
41 | cd $SRCTREE |
42 | cp $MYFILE $MYFILE.orig |
43 | vi $MYFILE # make your change |
44 | cd .. |
45 | diff -up $SRCTREE/$MYFILE{.orig,} > /tmp/patch |
46 | |
47 | To create a patch for multiple files, you should unpack a "vanilla", |
48 | or unmodified kernel source tree, and generate a diff against your |
49 | own source tree. For example: |
50 | |
51 | MYSRC= /devel/linux-2.4 |
52 | |
53 | tar xvfz linux-2.4.0-test11.tar.gz |
54 | mv linux linux-vanilla |
55 | wget http://www.moses.uklinux.net/patches/dontdiff |
56 | diff -uprN -X dontdiff linux-vanilla $MYSRC > /tmp/patch |
57 | rm -f dontdiff |
58 | |
59 | "dontdiff" is a list of files which are generated by the kernel during |
60 | the build process, and should be ignored in any diff(1)-generated |
61 | patch. dontdiff is maintained by Tigran Aivazian <tigran@veritas.com> |
62 | |
63 | Make sure your patch does not include any extra files which do not |
64 | belong in a patch submission. Make sure to review your patch -after- |
65 | generated it with diff(1), to ensure accuracy. |
66 | |
67 | If your changes produce a lot of deltas, you may want to look into |
68 | splitting them into individual patches which modify things in |
69 | logical stages, this will facilitate easier reviewing by other |
70 | kernel developers, very important if you want your patch accepted. |
71 | There are a number of scripts which can aid in this; |
72 | |
73 | Quilt: |
74 | http://savannah.nongnu.org/projects/quilt |
75 | |
76 | Randy Dunlap's patch scripts: |
77 | http://developer.osdl.org/rddunlap/scripts/patching-scripts.tgz |
78 | |
79 | Andrew Morton's patch scripts: |
80 | http://www.zip.com.au/~akpm/linux/patches/patch-scripts-0.16 |
81 | |
82 | 2) Describe your changes. |
83 | |
84 | Describe the technical detail of the change(s) your patch includes. |
85 | |
86 | Be as specific as possible. The WORST descriptions possible include |
87 | things like "update driver X", "bug fix for driver X", or "this patch |
88 | includes updates for subsystem X. Please apply." |
89 | |
90 | If your description starts to get long, that's a sign that you probably |
91 | need to split up your patch. See #3, next. |
92 | |
93 | |
94 | |
95 | 3) Separate your changes. |
96 | |
97 | Separate each logical change into its own patch. |
98 | |
99 | For example, if your changes include both bug fixes and performance |
100 | enhancements for a single driver, separate those changes into two |
101 | or more patches. If your changes include an API update, and a new |
102 | driver which uses that new API, separate those into two patches. |
103 | |
104 | On the other hand, if you make a single change to numerous files, |
105 | group those changes into a single patch. Thus a single logical change |
106 | is contained within a single patch. |
107 | |
108 | If one patch depends on another patch in order for a change to be |
109 | complete, that is OK. Simply note "this patch depends on patch X" |
110 | in your patch description. |
111 | |
112 | |
113 | 4) Select e-mail destination. |
114 | |
115 | Look through the MAINTAINERS file and the source code, and determine |
116 | if your change applies to a specific subsystem of the kernel, with |
117 | an assigned maintainer. If so, e-mail that person. |
118 | |
119 | If no maintainer is listed, or the maintainer does not respond, send |
120 | your patch to the primary Linux kernel developer's mailing list, |
121 | linux-kernel@vger.kernel.org. Most kernel developers monitor this |
122 | e-mail list, and can comment on your changes. |
123 | |
124 | Linus Torvalds is the final arbiter of all changes accepted into the |
125 | Linux kernel. His e-mail address is <torvalds@osdl.org>. He gets |
126 | a lot of e-mail, so typically you should do your best to -avoid- sending |
127 | him e-mail. |
128 | |
129 | Patches which are bug fixes, are "obvious" changes, or similarly |
130 | require little discussion should be sent or CC'd to Linus. Patches |
131 | which require discussion or do not have a clear advantage should |
132 | usually be sent first to linux-kernel. Only after the patch is |
133 | discussed should the patch then be submitted to Linus. |
134 | |
135 | For small patches you may want to CC the Trivial Patch Monkey |
136 | trivial@rustcorp.com.au set up by Rusty Russell; which collects "trivial" |
137 | patches. Trivial patches must qualify for one of the following rules: |
138 | Spelling fixes in documentation |
139 | Spelling fixes which could break grep(1). |
140 | Warning fixes (cluttering with useless warnings is bad) |
141 | Compilation fixes (only if they are actually correct) |
142 | Runtime fixes (only if they actually fix things) |
143 | Removing use of deprecated functions/macros (eg. check_region). |
144 | Contact detail and documentation fixes |
145 | Non-portable code replaced by portable code (even in arch-specific, |
146 | since people copy, as long as it's trivial) |
147 | Any fix by the author/maintainer of the file. (ie. patch monkey |
148 | in re-transmission mode) |
149 | |
150 | |
151 | |
152 | 5) Select your CC (e-mail carbon copy) list. |
153 | |
154 | Unless you have a reason NOT to do so, CC linux-kernel@vger.kernel.org. |
155 | |
156 | Other kernel developers besides Linus need to be aware of your change, |
157 | so that they may comment on it and offer code review and suggestions. |
158 | linux-kernel is the primary Linux kernel developer mailing list. |
159 | Other mailing lists are available for specific subsystems, such as |
160 | USB, framebuffer devices, the VFS, the SCSI subsystem, etc. See the |
161 | MAINTAINERS file for a mailing list that relates specifically to |
162 | your change. |
163 | |
164 | Even if the maintainer did not respond in step #4, make sure to ALWAYS |
165 | copy the maintainer when you change their code. |
166 | |
167 | For small patches you may want to CC the Trivial Patch Monkey |
168 | trivial@rustcorp.com.au set up by Rusty Russell; which collects "trivial" |
169 | patches. Trivial patches must qualify for one of the following rules: |
170 | Spelling fixes in documentation |
171 | Spelling fixes which could break grep(1). |
172 | Warning fixes (cluttering with useless warnings is bad) |
173 | Compilation fixes (only if they are actually correct) |
174 | Runtime fixes (only if they actually fix things) |
175 | Removing use of deprecated functions/macros (eg. check_region). |
176 | Contact detail and documentation fixes |
177 | Non-portable code replaced by portable code (even in arch-specific, |
178 | since people copy, as long as it's trivial) |
179 | Any fix by the author/maintainer of the file. (ie. patch monkey |
180 | in re-transmission mode) |
181 | |
182 | |
183 | |
184 | 6) No MIME, no links, no compression, no attachments. Just plain text. |
185 | |
186 | Linus and other kernel developers need to be able to read and comment |
187 | on the changes you are submitting. It is important for a kernel |
188 | developer to be able to "quote" your changes, using standard e-mail |
189 | tools, so that they may comment on specific portions of your code. |
190 | |
191 | For this reason, all patches should be submitting e-mail "inline". |
192 | WARNING: Be wary of your editor's word-wrap corrupting your patch, |
193 | if you choose to cut-n-paste your patch. |
194 | |
195 | Do not attach the patch as a MIME attachment, compressed or not. |
196 | Many popular e-mail applications will not always transmit a MIME |
197 | attachment as plain text, making it impossible to comment on your |
198 | code. A MIME attachment also takes Linus a bit more time to process, |
199 | decreasing the likelihood of your MIME-attached change being accepted. |
200 | |
201 | Exception: If your mailer is mangling patches then someone may ask |
202 | you to re-send them using MIME. |
203 | |
204 | |
205 | |
206 | 7) E-mail size. |
207 | |
208 | When sending patches to Linus, always follow step #6. |
209 | |
210 | Large changes are not appropriate for mailing lists, and some |
211 | maintainers. If your patch, uncompressed, exceeds 40 kB in size, |
212 | it is preferred that you store your patch on an Internet-accessible |
213 | server, and provide instead a URL (link) pointing to your patch. |
214 | |
215 | |
216 | |
217 | 8) Name your kernel version. |
218 | |
219 | It is important to note, either in the subject line or in the patch |
220 | description, the kernel version to which this patch applies. |
221 | |
222 | If the patch does not apply cleanly to the latest kernel version, |
223 | Linus will not apply it. |
224 | |
225 | |
226 | |
227 | 9) Don't get discouraged. Re-submit. |
228 | |
229 | After you have submitted your change, be patient and wait. If Linus |
230 | likes your change and applies it, it will appear in the next version |
231 | of the kernel that he releases. |
232 | |
233 | However, if your change doesn't appear in the next version of the |
234 | kernel, there could be any number of reasons. It's YOUR job to |
235 | narrow down those reasons, correct what was wrong, and submit your |
236 | updated change. |
237 | |
238 | It is quite common for Linus to "drop" your patch without comment. |
239 | That's the nature of the system. If he drops your patch, it could be |
240 | due to |
241 | * Your patch did not apply cleanly to the latest kernel version |
242 | * Your patch was not sufficiently discussed on linux-kernel. |
243 | * A style issue (see section 2), |
244 | * An e-mail formatting issue (re-read this section) |
245 | * A technical problem with your change |
246 | * He gets tons of e-mail, and yours got lost in the shuffle |
247 | * You are being annoying (See Figure 1) |
248 | |
249 | When in doubt, solicit comments on linux-kernel mailing list. |
250 | |
251 | |
252 | |
253 | 10) Include PATCH in the subject |
254 | |
255 | Due to high e-mail traffic to Linus, and to linux-kernel, it is common |
256 | convention to prefix your subject line with [PATCH]. This lets Linus |
257 | and other kernel developers more easily distinguish patches from other |
258 | e-mail discussions. |
259 | |
260 | |
261 | |
262 | 11) Sign your work |
263 | |
264 | To improve tracking of who did what, especially with patches that can |
265 | percolate to their final resting place in the kernel through several |
266 | layers of maintainers, we've introduced a "sign-off" procedure on |
267 | patches that are being emailed around. |
268 | |
269 | The sign-off is a simple line at the end of the explanation for the |
270 | patch, which certifies that you wrote it or otherwise have the right to |
271 | pass it on as a open-source patch. The rules are pretty simple: if you |
272 | can certify the below: |
273 | |
274 | Developer's Certificate of Origin 1.1 |
275 | |
276 | By making a contribution to this project, I certify that: |
277 | |
278 | (a) The contribution was created in whole or in part by me and I |
279 | have the right to submit it under the open source license |
280 | indicated in the file; or |
281 | |
282 | (b) The contribution is based upon previous work that, to the best |
283 | of my knowledge, is covered under an appropriate open source |
284 | license and I have the right under that license to submit that |
285 | work with modifications, whether created in whole or in part |
286 | by me, under the same open source license (unless I am |
287 | permitted to submit under a different license), as indicated |
288 | in the file; or |
289 | |
290 | (c) The contribution was provided directly to me by some other |
291 | person who certified (a), (b) or (c) and I have not modified |
292 | it. |
293 | |
294 | (d) I understand and agree that this project and the contribution |
295 | are public and that a record of the contribution (including all |
296 | personal information I submit with it, including my sign-off) is |
297 | maintained indefinitely and may be redistributed consistent with |
298 | this project or the open source license(s) involved. |
299 | |
300 | then you just add a line saying |
301 | |
302 | Signed-off-by: Random J Developer <random@developer.org> |
303 | |
304 | Some people also put extra tags at the end. They'll just be ignored for |
305 | now, but you can do this to mark internal company procedures or just |
306 | point out some special detail about the sign-off. |
307 | |
308 | |
309 | ----------------------------------- |
310 | SECTION 2 - HINTS, TIPS, AND TRICKS |
311 | ----------------------------------- |
312 | |
313 | This section lists many of the common "rules" associated with code |
314 | submitted to the kernel. There are always exceptions... but you must |
315 | have a really good reason for doing so. You could probably call this |
316 | section Linus Computer Science 101. |
317 | |
318 | |
319 | |
320 | 1) Read Documentation/CodingStyle |
321 | |
322 | Nuff said. If your code deviates too much from this, it is likely |
323 | to be rejected without further review, and without comment. |
324 | |
325 | |
326 | |
327 | 2) #ifdefs are ugly |
328 | |
329 | Code cluttered with ifdefs is difficult to read and maintain. Don't do |
330 | it. Instead, put your ifdefs in a header, and conditionally define |
331 | 'static inline' functions, or macros, which are used in the code. |
332 | Let the compiler optimize away the "no-op" case. |
333 | |
334 | Simple example, of poor code: |
335 | |
336 | dev = alloc_etherdev (sizeof(struct funky_private)); |
337 | if (!dev) |
338 | return -ENODEV; |
339 | #ifdef CONFIG_NET_FUNKINESS |
340 | init_funky_net(dev); |
341 | #endif |
342 | |
343 | Cleaned-up example: |
344 | |
345 | (in header) |
346 | #ifndef CONFIG_NET_FUNKINESS |
347 | static inline void init_funky_net (struct net_device *d) {} |
348 | #endif |
349 | |
350 | (in the code itself) |
351 | dev = alloc_etherdev (sizeof(struct funky_private)); |
352 | if (!dev) |
353 | return -ENODEV; |
354 | init_funky_net(dev); |
355 | |
356 | |
357 | |
358 | 3) 'static inline' is better than a macro |
359 | |
360 | Static inline functions are greatly preferred over macros. |
361 | They provide type safety, have no length limitations, no formatting |
362 | limitations, and under gcc they are as cheap as macros. |
363 | |
364 | Macros should only be used for cases where a static inline is clearly |
365 | suboptimal [there a few, isolated cases of this in fast paths], |
366 | or where it is impossible to use a static inline function [such as |
367 | string-izing]. |
368 | |
369 | 'static inline' is preferred over 'static __inline__', 'extern inline', |
370 | and 'extern __inline__'. |
371 | |
372 | |
373 | |
374 | 4) Don't over-design. |
375 | |
376 | Don't try to anticipate nebulous future cases which may or may not |
377 | be useful: "Make it as simple as you can, and no simpler" |
378 | |
379 | |
380 |