view Documentation/SubmittingPatches @ 452:c7ed6fe5dca0

kexec: dont initialise regions in reserve_memory()

There is no need to initialise efi_memmap_res and boot_param_res in
reserve_memory() for the initial xen domain as it is done in
machine_kexec_setup_resources() using values from the kexec hypercall.

Signed-off-by: Simon Horman <horms@verge.net.au>
author Keir Fraser <keir.fraser@citrix.com>
date Thu Feb 28 10:55:18 2008 +0000 (2008-02-28)
parents 831230e53067
line source
2 How to Get Your Change Into the Linux Kernel
3 or
4 Care And Operation Of Your Linus Torvalds
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.
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.
19 --------------------------------------------
21 --------------------------------------------
25 1) "diff -up"
26 ------------
28 Use "diff -up" or "diff -uprN" to create patches.
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.
38 To create a patch for a single file, it is often sufficient to do:
40 SRCTREE= linux-2.6
41 MYFILE= drivers/net/mydriver.c
43 cd $SRCTREE
44 cp $MYFILE $MYFILE.orig
45 vi $MYFILE # make your change
46 cd ..
47 diff -up $SRCTREE/$MYFILE{.orig,} > /tmp/patch
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:
53 MYSRC= /devel/linux-2.6
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
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>.
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.
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:
76 Quilt:
77 http://savannah.nongnu.org/projects/quilt
79 Andrew Morton's patch scripts:
80 http://www.zip.com.au/~akpm/linux/patches/
81 Instead of these scripts, quilt is the recommended patch management
82 tool (see above).
86 2) Describe your changes.
88 Describe the technical detail of the change(s) your patch includes.
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."
94 If your description starts to get long, that's a sign that you probably
95 need to split up your patch. See #3, next.
99 3) Separate your changes.
101 Separate _logical changes_ into a single patch file.
103 For example, if your changes include both bug fixes and performance
104 enhancements for a single driver, separate those changes into two
105 or more patches. If your changes include an API update, and a new
106 driver which uses that new API, separate those into two patches.
108 On the other hand, if you make a single change to numerous files,
109 group those changes into a single patch. Thus a single logical change
110 is contained within a single patch.
112 If one patch depends on another patch in order for a change to be
113 complete, that is OK. Simply note "this patch depends on patch X"
114 in your patch description.
116 If you cannot condense your patch set into a smaller set of patches,
117 then only post say 15 or so at a time and wait for review and integration.
121 4) Select e-mail destination.
123 Look through the MAINTAINERS file and the source code, and determine
124 if your change applies to a specific subsystem of the kernel, with
125 an assigned maintainer. If so, e-mail that person.
127 If no maintainer is listed, or the maintainer does not respond, send
128 your patch to the primary Linux kernel developer's mailing list,
129 linux-kernel@vger.kernel.org. Most kernel developers monitor this
130 e-mail list, and can comment on your changes.
133 Do not send more than 15 patches at once to the vger mailing lists!!!
136 Linus Torvalds is the final arbiter of all changes accepted into the
137 Linux kernel. His e-mail address is <torvalds@osdl.org>. He gets
138 a lot of e-mail, so typically you should do your best to -avoid- sending
139 him e-mail.
141 Patches which are bug fixes, are "obvious" changes, or similarly
142 require little discussion should be sent or CC'd to Linus. Patches
143 which require discussion or do not have a clear advantage should
144 usually be sent first to linux-kernel. Only after the patch is
145 discussed should the patch then be submitted to Linus.
149 5) Select your CC (e-mail carbon copy) list.
151 Unless you have a reason NOT to do so, CC linux-kernel@vger.kernel.org.
153 Other kernel developers besides Linus need to be aware of your change,
154 so that they may comment on it and offer code review and suggestions.
155 linux-kernel is the primary Linux kernel developer mailing list.
156 Other mailing lists are available for specific subsystems, such as
157 USB, framebuffer devices, the VFS, the SCSI subsystem, etc. See the
158 MAINTAINERS file for a mailing list that relates specifically to
159 your change.
161 Majordomo lists of VGER.KERNEL.ORG at:
162 <http://vger.kernel.org/vger-lists.html>
164 If changes affect userland-kernel interfaces, please send
165 the MAN-PAGES maintainer (as listed in the MAINTAINERS file)
166 a man-pages patch, or at least a notification of the change,
167 so that some information makes its way into the manual pages.
169 Even if the maintainer did not respond in step #4, make sure to ALWAYS
170 copy the maintainer when you change their code.
172 For small patches you may want to CC the Trivial Patch Monkey
173 trivial@kernel.org managed by Adrian Bunk; which collects "trivial"
174 patches. Trivial patches must qualify for one of the following rules:
175 Spelling fixes in documentation
176 Spelling fixes which could break grep(1).
177 Warning fixes (cluttering with useless warnings is bad)
178 Compilation fixes (only if they are actually correct)
179 Runtime fixes (only if they actually fix things)
180 Removing use of deprecated functions/macros (eg. check_region).
181 Contact detail and documentation fixes
182 Non-portable code replaced by portable code (even in arch-specific,
183 since people copy, as long as it's trivial)
184 Any fix by the author/maintainer of the file. (ie. patch monkey
185 in re-transmission mode)
186 URL: <http://www.kernel.org/pub/linux/kernel/people/bunk/trivial/>
191 6) No MIME, no links, no compression, no attachments. Just plain text.
193 Linus and other kernel developers need to be able to read and comment
194 on the changes you are submitting. It is important for a kernel
195 developer to be able to "quote" your changes, using standard e-mail
196 tools, so that they may comment on specific portions of your code.
198 For this reason, all patches should be submitting e-mail "inline".
199 WARNING: Be wary of your editor's word-wrap corrupting your patch,
200 if you choose to cut-n-paste your patch.
202 Do not attach the patch as a MIME attachment, compressed or not.
203 Many popular e-mail applications will not always transmit a MIME
204 attachment as plain text, making it impossible to comment on your
205 code. A MIME attachment also takes Linus a bit more time to process,
206 decreasing the likelihood of your MIME-attached change being accepted.
208 Exception: If your mailer is mangling patches then someone may ask
209 you to re-send them using MIME.
213 7) E-mail size.
215 When sending patches to Linus, always follow step #6.
217 Large changes are not appropriate for mailing lists, and some
218 maintainers. If your patch, uncompressed, exceeds 40 kB in size,
219 it is preferred that you store your patch on an Internet-accessible
220 server, and provide instead a URL (link) pointing to your patch.
224 8) Name your kernel version.
226 It is important to note, either in the subject line or in the patch
227 description, the kernel version to which this patch applies.
229 If the patch does not apply cleanly to the latest kernel version,
230 Linus will not apply it.
234 9) Don't get discouraged. Re-submit.
236 After you have submitted your change, be patient and wait. If Linus
237 likes your change and applies it, it will appear in the next version
238 of the kernel that he releases.
240 However, if your change doesn't appear in the next version of the
241 kernel, there could be any number of reasons. It's YOUR job to
242 narrow down those reasons, correct what was wrong, and submit your
243 updated change.
245 It is quite common for Linus to "drop" your patch without comment.
246 That's the nature of the system. If he drops your patch, it could be
247 due to
248 * Your patch did not apply cleanly to the latest kernel version
249 * Your patch was not sufficiently discussed on linux-kernel.
250 * A style issue (see section 2),
251 * An e-mail formatting issue (re-read this section)
252 * A technical problem with your change
253 * He gets tons of e-mail, and yours got lost in the shuffle
254 * You are being annoying (See Figure 1)
256 When in doubt, solicit comments on linux-kernel mailing list.
260 10) Include PATCH in the subject
262 Due to high e-mail traffic to Linus, and to linux-kernel, it is common
263 convention to prefix your subject line with [PATCH]. This lets Linus
264 and other kernel developers more easily distinguish patches from other
265 e-mail discussions.
269 11) Sign your work
271 To improve tracking of who did what, especially with patches that can
272 percolate to their final resting place in the kernel through several
273 layers of maintainers, we've introduced a "sign-off" procedure on
274 patches that are being emailed around.
276 The sign-off is a simple line at the end of the explanation for the
277 patch, which certifies that you wrote it or otherwise have the right to
278 pass it on as a open-source patch. The rules are pretty simple: if you
279 can certify the below:
281 Developer's Certificate of Origin 1.1
283 By making a contribution to this project, I certify that:
285 (a) The contribution was created in whole or in part by me and I
286 have the right to submit it under the open source license
287 indicated in the file; or
289 (b) The contribution is based upon previous work that, to the best
290 of my knowledge, is covered under an appropriate open source
291 license and I have the right under that license to submit that
292 work with modifications, whether created in whole or in part
293 by me, under the same open source license (unless I am
294 permitted to submit under a different license), as indicated
295 in the file; or
297 (c) The contribution was provided directly to me by some other
298 person who certified (a), (b) or (c) and I have not modified
299 it.
301 (d) I understand and agree that this project and the contribution
302 are public and that a record of the contribution (including all
303 personal information I submit with it, including my sign-off) is
304 maintained indefinitely and may be redistributed consistent with
305 this project or the open source license(s) involved.
307 then you just add a line saying
309 Signed-off-by: Random J Developer <random@developer.example.org>
311 using your real name (sorry, no pseudonyms or anonymous contributions.)
313 Some people also put extra tags at the end. They'll just be ignored for
314 now, but you can do this to mark internal company procedures or just
315 point out some special detail about the sign-off.
318 12) The canonical patch format
320 The canonical patch subject line is:
322 Subject: [PATCH 001/123] subsystem: summary phrase
324 The canonical patch message body contains the following:
326 - A "from" line specifying the patch author.
328 - An empty line.
330 - The body of the explanation, which will be copied to the
331 permanent changelog to describe this patch.
333 - The "Signed-off-by:" lines, described above, which will
334 also go in the changelog.
336 - A marker line containing simply "---".
338 - Any additional comments not suitable for the changelog.
340 - The actual patch (diff output).
342 The Subject line format makes it very easy to sort the emails
343 alphabetically by subject line - pretty much any email reader will
344 support that - since because the sequence number is zero-padded,
345 the numerical and alphabetic sort is the same.
347 The "subsystem" in the email's Subject should identify which
348 area or subsystem of the kernel is being patched.
350 The "summary phrase" in the email's Subject should concisely
351 describe the patch which that email contains. The "summary
352 phrase" should not be a filename. Do not use the same "summary
353 phrase" for every patch in a whole patch series.
355 Bear in mind that the "summary phrase" of your email becomes
356 a globally-unique identifier for that patch. It propagates
357 all the way into the git changelog. The "summary phrase" may
358 later be used in developer discussions which refer to the patch.
359 People will want to google for the "summary phrase" to read
360 discussion regarding that patch.
362 A couple of example Subjects:
364 Subject: [patch 2/5] ext2: improve scalability of bitmap searching
365 Subject: [PATCHv2 001/207] x86: fix eflags tracking
367 The "from" line must be the very first line in the message body,
368 and has the form:
370 From: Original Author <author@example.com>
372 The "from" line specifies who will be credited as the author of the
373 patch in the permanent changelog. If the "from" line is missing,
374 then the "From:" line from the email header will be used to determine
375 the patch author in the changelog.
377 The explanation body will be committed to the permanent source
378 changelog, so should make sense to a competent reader who has long
379 since forgotten the immediate details of the discussion that might
380 have led to this patch.
382 The "---" marker line serves the essential purpose of marking for patch
383 handling tools where the changelog message ends.
385 One good use for the additional comments after the "---" marker is for
386 a diffstat, to show what files have changed, and the number of inserted
387 and deleted lines per file. A diffstat is especially useful on bigger
388 patches. Other comments relevant only to the moment or the maintainer,
389 not suitable for the permanent changelog, should also go here.
390 Use diffstat options "-p 1 -w 70" so that filenames are listed from the
391 top of the kernel source tree and don't use too much horizontal space
392 (easily fit in 80 columns, maybe with some indentation).
394 See more details on the proper patch format in the following
395 references.
400 -----------------------------------
402 -----------------------------------
404 This section lists many of the common "rules" associated with code
405 submitted to the kernel. There are always exceptions... but you must
406 have a really good reason for doing so. You could probably call this
407 section Linus Computer Science 101.
411 1) Read Documentation/CodingStyle
413 Nuff said. If your code deviates too much from this, it is likely
414 to be rejected without further review, and without comment.
418 2) #ifdefs are ugly
420 Code cluttered with ifdefs is difficult to read and maintain. Don't do
421 it. Instead, put your ifdefs in a header, and conditionally define
422 'static inline' functions, or macros, which are used in the code.
423 Let the compiler optimize away the "no-op" case.
425 Simple example, of poor code:
427 dev = alloc_etherdev (sizeof(struct funky_private));
428 if (!dev)
429 return -ENODEV;
431 init_funky_net(dev);
432 #endif
434 Cleaned-up example:
436 (in header)
438 static inline void init_funky_net (struct net_device *d) {}
439 #endif
441 (in the code itself)
442 dev = alloc_etherdev (sizeof(struct funky_private));
443 if (!dev)
444 return -ENODEV;
445 init_funky_net(dev);
449 3) 'static inline' is better than a macro
451 Static inline functions are greatly preferred over macros.
452 They provide type safety, have no length limitations, no formatting
453 limitations, and under gcc they are as cheap as macros.
455 Macros should only be used for cases where a static inline is clearly
456 suboptimal [there a few, isolated cases of this in fast paths],
457 or where it is impossible to use a static inline function [such as
458 string-izing].
460 'static inline' is preferred over 'static __inline__', 'extern inline',
461 and 'extern __inline__'.
465 4) Don't over-design.
467 Don't try to anticipate nebulous future cases which may or may not
468 be useful: "Make it as simple as you can, and no simpler."
472 ----------------------
474 ----------------------
476 Andrew Morton, "The perfect patch" (tpp).
477 <http://www.zip.com.au/~akpm/linux/patches/stuff/tpp.txt>
479 Jeff Garzik, "Linux kernel patch submission format."
480 <http://linux.yyz.us/patch-format.html>
482 Greg Kroah-Hartman "How to piss off a kernel subsystem maintainer".
483 <http://www.kroah.com/log/2005/03/31/>
484 <http://www.kroah.com/log/2005/07/08/>
485 <http://www.kroah.com/log/2005/10/19/>
486 <http://www.kroah.com/log/2006/01/11/>
488 NO!!!! No more huge patch bombs to linux-kernel@vger.kernel.org people!
489 <http://marc.theaimsgroup.com/?l=linux-kernel&m=112112749912944&w=2>
491 Kernel Documentation/CodingStyle
492 <http://sosdg.org/~coywolf/lxr/source/Documentation/CodingStyle>
494 Linus Torvald's mail on the canonical patch format:
495 <http://lkml.org/lkml/2005/4/7/183>
496 --