1 .. _submittingpatches: 1 .. _submittingpatches:
2 2
3 Submitting patches: the essential guide to get 3 Submitting patches: the essential guide to getting your code into the kernel
4 ============================================== 4 ============================================================================
5 5
6 For a person or company who wishes to submit a 6 For a person or company who wishes to submit a change to the Linux
7 kernel, the process can sometimes be daunting 7 kernel, the process can sometimes be daunting if you're not familiar
8 with "the system." This text is a collection 8 with "the system." This text is a collection of suggestions which
9 can greatly increase the chances of your chang 9 can greatly increase the chances of your change being accepted.
10 10
11 This document contains a large number of sugge 11 This document contains a large number of suggestions in a relatively terse
12 format. For detailed information on how the k 12 format. For detailed information on how the kernel development process
13 works, see Documentation/process/development-p 13 works, see Documentation/process/development-process.rst. Also, read
14 Documentation/process/submit-checklist.rst 14 Documentation/process/submit-checklist.rst
15 for a list of items to check before submitting !! 15 for a list of items to check before submitting code. If you are submitting
16 For device tree binding patches, read !! 16 a driver, also read Documentation/process/submitting-drivers.rst; for device
17 Documentation/devicetree/bindings/submitting-p !! 17 tree binding patches, read Documentation/process/submitting-patches.rst.
18 18
19 This documentation assumes that you're using ` 19 This documentation assumes that you're using ``git`` to prepare your patches.
20 If you're unfamiliar with ``git``, you would b 20 If you're unfamiliar with ``git``, you would be well-advised to learn how to
21 use it, it will make your life as a kernel dev 21 use it, it will make your life as a kernel developer and in general much
22 easier. 22 easier.
23 23
24 Some subsystems and maintainer trees have addi <<
25 their workflow and expectations, see <<
26 :ref:`Documentation/process/maintainer-handboo <<
27 <<
28 Obtain a current source tree 24 Obtain a current source tree
29 ---------------------------- 25 ----------------------------
30 26
31 If you do not have a repository with the curre 27 If you do not have a repository with the current kernel source handy, use
32 ``git`` to obtain one. You'll want to start w 28 ``git`` to obtain one. You'll want to start with the mainline repository,
33 which can be grabbed with:: 29 which can be grabbed with::
34 30
35 git clone git://git.kernel.org/pub/scm/linux 31 git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
36 32
37 Note, however, that you may not want to develo 33 Note, however, that you may not want to develop against the mainline tree
38 directly. Most subsystem maintainers run thei 34 directly. Most subsystem maintainers run their own trees and want to see
39 patches prepared against those trees. See the 35 patches prepared against those trees. See the **T:** entry for the subsystem
40 in the MAINTAINERS file to find that tree, or 36 in the MAINTAINERS file to find that tree, or simply ask the maintainer if
41 the tree is not listed there. 37 the tree is not listed there.
42 38
43 .. _describe_changes: 39 .. _describe_changes:
44 40
45 Describe your changes 41 Describe your changes
46 --------------------- 42 ---------------------
47 43
48 Describe your problem. Whether your patch is 44 Describe your problem. Whether your patch is a one-line bug fix or
49 5000 lines of a new feature, there must be an 45 5000 lines of a new feature, there must be an underlying problem that
50 motivated you to do this work. Convince the r 46 motivated you to do this work. Convince the reviewer that there is a
51 problem worth fixing and that it makes sense f 47 problem worth fixing and that it makes sense for them to read past the
52 first paragraph. 48 first paragraph.
53 49
54 Describe user-visible impact. Straight up cra 50 Describe user-visible impact. Straight up crashes and lockups are
55 pretty convincing, but not all bugs are that b 51 pretty convincing, but not all bugs are that blatant. Even if the
56 problem was spotted during code review, descri 52 problem was spotted during code review, describe the impact you think
57 it can have on users. Keep in mind that the m 53 it can have on users. Keep in mind that the majority of Linux
58 installations run kernels from secondary stabl 54 installations run kernels from secondary stable trees or
59 vendor/product-specific trees that cherry-pick 55 vendor/product-specific trees that cherry-pick only specific patches
60 from upstream, so include anything that could 56 from upstream, so include anything that could help route your change
61 downstream: provoking circumstances, excerpts 57 downstream: provoking circumstances, excerpts from dmesg, crash
62 descriptions, performance regressions, latency 58 descriptions, performance regressions, latency spikes, lockups, etc.
63 59
64 Quantify optimizations and trade-offs. If you 60 Quantify optimizations and trade-offs. If you claim improvements in
65 performance, memory consumption, stack footpri 61 performance, memory consumption, stack footprint, or binary size,
66 include numbers that back them up. But also d 62 include numbers that back them up. But also describe non-obvious
67 costs. Optimizations usually aren't free but 63 costs. Optimizations usually aren't free but trade-offs between CPU,
68 memory, and readability; or, when it comes to 64 memory, and readability; or, when it comes to heuristics, between
69 different workloads. Describe the expected do 65 different workloads. Describe the expected downsides of your
70 optimization so that the reviewer can weigh co 66 optimization so that the reviewer can weigh costs against benefits.
71 67
72 Once the problem is established, describe what 68 Once the problem is established, describe what you are actually doing
73 about it in technical detail. It's important 69 about it in technical detail. It's important to describe the change
74 in plain English for the reviewer to verify th 70 in plain English for the reviewer to verify that the code is behaving
75 as you intend it to. 71 as you intend it to.
76 72
77 The maintainer will thank you if you write you 73 The maintainer will thank you if you write your patch description in a
78 form which can be easily pulled into Linux's s 74 form which can be easily pulled into Linux's source code management
79 system, ``git``, as a "commit log". See :ref: !! 75 system, ``git``, as a "commit log". See :ref:`explicit_in_reply_to`.
80 76
81 Solve only one problem per patch. If your des 77 Solve only one problem per patch. If your description starts to get
82 long, that's a sign that you probably need to 78 long, that's a sign that you probably need to split up your patch.
83 See :ref:`split_changes`. 79 See :ref:`split_changes`.
84 80
85 When you submit or resubmit a patch or patch s 81 When you submit or resubmit a patch or patch series, include the
86 complete patch description and justification f 82 complete patch description and justification for it. Don't just
87 say that this is version N of the patch (serie 83 say that this is version N of the patch (series). Don't expect the
88 subsystem maintainer to refer back to earlier 84 subsystem maintainer to refer back to earlier patch versions or referenced
89 URLs to find the patch description and put tha 85 URLs to find the patch description and put that into the patch.
90 I.e., the patch (series) and its description s 86 I.e., the patch (series) and its description should be self-contained.
91 This benefits both the maintainers and reviewe 87 This benefits both the maintainers and reviewers. Some reviewers
92 probably didn't even receive earlier versions 88 probably didn't even receive earlier versions of the patch.
93 89
94 Describe your changes in imperative mood, e.g. 90 Describe your changes in imperative mood, e.g. "make xyzzy do frotz"
95 instead of "[This patch] makes xyzzy do frotz" 91 instead of "[This patch] makes xyzzy do frotz" or "[I] changed xyzzy
96 to do frotz", as if you are giving orders to t 92 to do frotz", as if you are giving orders to the codebase to change
97 its behaviour. 93 its behaviour.
98 94
>> 95 If the patch fixes a logged bug entry, refer to that bug entry by
>> 96 number and URL. If the patch follows from a mailing list discussion,
>> 97 give a URL to the mailing list archive; use the https://lkml.kernel.org/
>> 98 redirector with a ``Message-Id``, to ensure that the links cannot become
>> 99 stale.
>> 100
>> 101 However, try to make your explanation understandable without external
>> 102 resources. In addition to giving a URL to a mailing list archive or
>> 103 bug, summarize the relevant points of the discussion that led to the
>> 104 patch as submitted.
>> 105
99 If you want to refer to a specific commit, don 106 If you want to refer to a specific commit, don't just refer to the
100 SHA-1 ID of the commit. Please also include th 107 SHA-1 ID of the commit. Please also include the oneline summary of
101 the commit, to make it easier for reviewers to 108 the commit, to make it easier for reviewers to know what it is about.
102 Example:: 109 Example::
103 110
104 Commit e21d2170f36602ae2708 ("video: r 111 Commit e21d2170f36602ae2708 ("video: remove unnecessary
105 platform_set_drvdata()") removed the u 112 platform_set_drvdata()") removed the unnecessary
106 platform_set_drvdata(), but left the v 113 platform_set_drvdata(), but left the variable "dev" unused,
107 delete it. 114 delete it.
108 115
109 You should also be sure to use at least the fi 116 You should also be sure to use at least the first twelve characters of the
110 SHA-1 ID. The kernel repository holds a *lot* 117 SHA-1 ID. The kernel repository holds a *lot* of objects, making
111 collisions with shorter IDs a real possibility 118 collisions with shorter IDs a real possibility. Bear in mind that, even if
112 there is no collision with your six-character 119 there is no collision with your six-character ID now, that condition may
113 change five years from now. 120 change five years from now.
114 121
115 If related discussions or any other background <<
116 can be found on the web, add 'Link:' tags poin <<
117 result of some earlier mailing list discussion <<
118 web, point to it. <<
119 <<
120 When linking to mailing list archives, prefera <<
121 message archiver service. To create the link U <<
122 ``Message-ID`` header of the message without t <<
123 For example:: <<
124 <<
125 Link: https://lore.kernel.org/30th.anniver <<
126 <<
127 Please check the link to make sure that it is <<
128 to the relevant message. <<
129 <<
130 However, try to make your explanation understa <<
131 resources. In addition to giving a URL to a ma <<
132 summarize the relevant points of the discussio <<
133 patch as submitted. <<
134 <<
135 In case your patch fixes a bug, use the 'Close <<
136 the report in the mailing list archives or a p <<
137 <<
138 Closes: https://example.com/issues/123 <<
139 <<
140 Some bug trackers have the ability to close is <<
141 commit with such a tag is applied. Some bots m <<
142 also track such tags and take certain actions. <<
143 invalid URLs are forbidden. <<
144 <<
145 If your patch fixes a bug in a specific commit 122 If your patch fixes a bug in a specific commit, e.g. you found an issue using
146 ``git bisect``, please use the 'Fixes:' tag wi 123 ``git bisect``, please use the 'Fixes:' tag with the first 12 characters of
147 the SHA-1 ID, and the one line summary. Do no 124 the SHA-1 ID, and the one line summary. Do not split the tag across multiple
148 lines, tags are exempt from the "wrap at 75 co 125 lines, tags are exempt from the "wrap at 75 columns" rule in order to simplify
149 parsing scripts. For example:: 126 parsing scripts. For example::
150 127
151 Fixes: 54a4f0239f2e ("KVM: MMU: make k 128 Fixes: 54a4f0239f2e ("KVM: MMU: make kvm_mmu_zap_page() return the number of pages it actually freed")
152 129
153 The following ``git config`` settings can be u 130 The following ``git config`` settings can be used to add a pretty format for
154 outputting the above style in the ``git log`` 131 outputting the above style in the ``git log`` or ``git show`` commands::
155 132
156 [core] 133 [core]
157 abbrev = 12 134 abbrev = 12
158 [pretty] 135 [pretty]
159 fixes = Fixes: %h (\"%s\") 136 fixes = Fixes: %h (\"%s\")
160 137
161 An example call:: 138 An example call::
162 139
163 $ git log -1 --pretty=fixes 54a4f0239f 140 $ git log -1 --pretty=fixes 54a4f0239f2e
164 Fixes: 54a4f0239f2e ("KVM: MMU: make k 141 Fixes: 54a4f0239f2e ("KVM: MMU: make kvm_mmu_zap_page() return the number of pages it actually freed")
165 142
166 .. _split_changes: 143 .. _split_changes:
167 144
168 Separate your changes 145 Separate your changes
169 --------------------- 146 ---------------------
170 147
171 Separate each **logical change** into a separa 148 Separate each **logical change** into a separate patch.
172 149
173 For example, if your changes include both bug 150 For example, if your changes include both bug fixes and performance
174 enhancements for a single driver, separate tho 151 enhancements for a single driver, separate those changes into two
175 or more patches. If your changes include an A 152 or more patches. If your changes include an API update, and a new
176 driver which uses that new API, separate those 153 driver which uses that new API, separate those into two patches.
177 154
178 On the other hand, if you make a single change 155 On the other hand, if you make a single change to numerous files,
179 group those changes into a single patch. Thus 156 group those changes into a single patch. Thus a single logical change
180 is contained within a single patch. 157 is contained within a single patch.
181 158
182 The point to remember is that each patch shoul 159 The point to remember is that each patch should make an easily understood
183 change that can be verified by reviewers. Eac 160 change that can be verified by reviewers. Each patch should be justifiable
184 on its own merits. 161 on its own merits.
185 162
186 If one patch depends on another patch in order 163 If one patch depends on another patch in order for a change to be
187 complete, that is OK. Simply note **"this pat 164 complete, that is OK. Simply note **"this patch depends on patch X"**
188 in your patch description. 165 in your patch description.
189 166
190 When dividing your change into a series of pat 167 When dividing your change into a series of patches, take special care to
191 ensure that the kernel builds and runs properl 168 ensure that the kernel builds and runs properly after each patch in the
192 series. Developers using ``git bisect`` to tr 169 series. Developers using ``git bisect`` to track down a problem can end up
193 splitting your patch series at any point; they 170 splitting your patch series at any point; they will not thank you if you
194 introduce bugs in the middle. 171 introduce bugs in the middle.
195 172
196 If you cannot condense your patch set into a s 173 If you cannot condense your patch set into a smaller set of patches,
197 then only post say 15 or so at a time and wait 174 then only post say 15 or so at a time and wait for review and integration.
198 175
199 176
200 177
201 Style-check your changes 178 Style-check your changes
202 ------------------------ 179 ------------------------
203 180
204 Check your patch for basic style violations, d 181 Check your patch for basic style violations, details of which can be
205 found in Documentation/process/coding-style.rs 182 found in Documentation/process/coding-style.rst.
206 Failure to do so simply wastes 183 Failure to do so simply wastes
207 the reviewers time and will get your patch rej 184 the reviewers time and will get your patch rejected, probably
208 without even being read. 185 without even being read.
209 186
210 One significant exception is when moving code 187 One significant exception is when moving code from one file to
211 another -- in this case you should not modify 188 another -- in this case you should not modify the moved code at all in
212 the same patch which moves it. This clearly d 189 the same patch which moves it. This clearly delineates the act of
213 moving the code and your changes. This greatl 190 moving the code and your changes. This greatly aids review of the
214 actual differences and allows tools to better 191 actual differences and allows tools to better track the history of
215 the code itself. 192 the code itself.
216 193
217 Check your patches with the patch style checke 194 Check your patches with the patch style checker prior to submission
218 (scripts/checkpatch.pl). Note, though, that t 195 (scripts/checkpatch.pl). Note, though, that the style checker should be
219 viewed as a guide, not as a replacement for hu 196 viewed as a guide, not as a replacement for human judgment. If your code
220 looks better with a violation then its probabl 197 looks better with a violation then its probably best left alone.
221 198
222 The checker reports at three levels: 199 The checker reports at three levels:
223 - ERROR: things that are very likely to be wr 200 - ERROR: things that are very likely to be wrong
224 - WARNING: things requiring careful review 201 - WARNING: things requiring careful review
225 - CHECK: things requiring thought 202 - CHECK: things requiring thought
226 203
227 You should be able to justify all violations t 204 You should be able to justify all violations that remain in your
228 patch. 205 patch.
229 206
230 207
231 Select the recipients for your patch 208 Select the recipients for your patch
232 ------------------------------------ 209 ------------------------------------
233 210
234 You should always copy the appropriate subsyst !! 211 You should always copy the appropriate subsystem maintainer(s) on any patch
235 any patch to code that they maintain; look thr !! 212 to code that they maintain; look through the MAINTAINERS file and the
236 source code revision history to see who those !! 213 source code revision history to see who those maintainers are. The
237 scripts/get_maintainer.pl can be very useful a !! 214 script scripts/get_maintainer.pl can be very useful at this step. If you
238 patches as arguments to scripts/get_maintainer !! 215 cannot find a maintainer for the subsystem you are working on, Andrew
239 maintainer for the subsystem you are working o !! 216 Morton (akpm@linux-foundation.org) serves as a maintainer of last resort.
240 (akpm@linux-foundation.org) serves as a mainta !! 217
241 !! 218 You should also normally choose at least one mailing list to receive a copy
242 linux-kernel@vger.kernel.org should be used by !! 219 of your patch set. linux-kernel@vger.kernel.org functions as a list of
243 volume on that list has caused a number of dev !! 220 last resort, but the volume on that list has caused a number of developers
244 do not spam unrelated lists and unrelated peop !! 221 to tune it out. Look in the MAINTAINERS file for a subsystem-specific
245 !! 222 list; your patch will probably get more attention there. Please do not
246 Many kernel-related lists are hosted at kernel !! 223 spam unrelated lists, though.
247 of them at https://subspace.kernel.org. There !! 224
248 hosted elsewhere as well, though. !! 225 Many kernel-related lists are hosted on vger.kernel.org; you can find a
>> 226 list of them at http://vger.kernel.org/vger-lists.html. There are
>> 227 kernel-related lists hosted elsewhere as well, though.
>> 228
>> 229 Do not send more than 15 patches at once to the vger mailing lists!!!
249 230
250 Linus Torvalds is the final arbiter of all cha 231 Linus Torvalds is the final arbiter of all changes accepted into the
251 Linux kernel. His e-mail address is <torvalds@ 232 Linux kernel. His e-mail address is <torvalds@linux-foundation.org>.
252 He gets a lot of e-mail, and, at this point, v 233 He gets a lot of e-mail, and, at this point, very few patches go through
253 Linus directly, so typically you should do you 234 Linus directly, so typically you should do your best to -avoid-
254 sending him e-mail. 235 sending him e-mail.
255 236
256 If you have a patch that fixes an exploitable 237 If you have a patch that fixes an exploitable security bug, send that patch
257 to security@kernel.org. For severe bugs, a sh 238 to security@kernel.org. For severe bugs, a short embargo may be considered
258 to allow distributors to get the patch out to 239 to allow distributors to get the patch out to users; in such cases,
259 obviously, the patch should not be sent to any 240 obviously, the patch should not be sent to any public lists. See also
260 Documentation/process/security-bugs.rst. !! 241 Documentation/admin-guide/security-bugs.rst.
261 242
262 Patches that fix a severe bug in a released ke 243 Patches that fix a severe bug in a released kernel should be directed
263 toward the stable maintainers by putting a lin 244 toward the stable maintainers by putting a line like this::
264 245
265 Cc: stable@vger.kernel.org 246 Cc: stable@vger.kernel.org
266 247
267 into the sign-off area of your patch (note, NO 248 into the sign-off area of your patch (note, NOT an email recipient). You
268 should also read Documentation/process/stable- 249 should also read Documentation/process/stable-kernel-rules.rst
269 in addition to this document. 250 in addition to this document.
270 251
271 If changes affect userland-kernel interfaces, 252 If changes affect userland-kernel interfaces, please send the MAN-PAGES
272 maintainer (as listed in the MAINTAINERS file) 253 maintainer (as listed in the MAINTAINERS file) a man-pages patch, or at
273 least a notification of the change, so that so 254 least a notification of the change, so that some information makes its way
274 into the manual pages. User-space API changes 255 into the manual pages. User-space API changes should also be copied to
275 linux-api@vger.kernel.org. 256 linux-api@vger.kernel.org.
276 257
>> 258 For small patches you may want to CC the Trivial Patch Monkey
>> 259 trivial@kernel.org which collects "trivial" patches. Have a look
>> 260 into the MAINTAINERS file for its current manager.
>> 261
>> 262 Trivial patches must qualify for one of the following rules:
>> 263
>> 264 - Spelling fixes in documentation
>> 265 - Spelling fixes for errors which could break :manpage:`grep(1)`
>> 266 - Warning fixes (cluttering with useless warnings is bad)
>> 267 - Compilation fixes (only if they are actually correct)
>> 268 - Runtime fixes (only if they actually fix things)
>> 269 - Removing use of deprecated functions/macros
>> 270 - Contact detail and documentation fixes
>> 271 - Non-portable code replaced by portable code (even in arch-specific,
>> 272 since people copy, as long as it's trivial)
>> 273 - Any fix by the author/maintainer of the file (ie. patch monkey
>> 274 in re-transmission mode)
>> 275
>> 276
277 277
278 No MIME, no links, no compression, no attachme 278 No MIME, no links, no compression, no attachments. Just plain text
279 ---------------------------------------------- 279 -------------------------------------------------------------------
280 280
281 Linus and other kernel developers need to be a 281 Linus and other kernel developers need to be able to read and comment
282 on the changes you are submitting. It is impo 282 on the changes you are submitting. It is important for a kernel
283 developer to be able to "quote" your changes, 283 developer to be able to "quote" your changes, using standard e-mail
284 tools, so that they may comment on specific po 284 tools, so that they may comment on specific portions of your code.
285 285
286 For this reason, all patches should be submitt 286 For this reason, all patches should be submitted by e-mail "inline". The
287 easiest way to do this is with ``git send-emai 287 easiest way to do this is with ``git send-email``, which is strongly
288 recommended. An interactive tutorial for ``gi 288 recommended. An interactive tutorial for ``git send-email`` is available at
289 https://git-send-email.io. 289 https://git-send-email.io.
290 290
291 If you choose not to use ``git send-email``: 291 If you choose not to use ``git send-email``:
292 292
293 .. warning:: 293 .. warning::
294 294
295 Be wary of your editor's word-wrap corruptin 295 Be wary of your editor's word-wrap corrupting your patch,
296 if you choose to cut-n-paste your patch. 296 if you choose to cut-n-paste your patch.
297 297
298 Do not attach the patch as a MIME attachment, 298 Do not attach the patch as a MIME attachment, compressed or not.
299 Many popular e-mail applications will not alwa 299 Many popular e-mail applications will not always transmit a MIME
300 attachment as plain text, making it impossible 300 attachment as plain text, making it impossible to comment on your
301 code. A MIME attachment also takes Linus a bi 301 code. A MIME attachment also takes Linus a bit more time to process,
302 decreasing the likelihood of your MIME-attache 302 decreasing the likelihood of your MIME-attached change being accepted.
303 303
304 Exception: If your mailer is mangling patches 304 Exception: If your mailer is mangling patches then someone may ask
305 you to re-send them using MIME. 305 you to re-send them using MIME.
306 306
307 See Documentation/process/email-clients.rst fo 307 See Documentation/process/email-clients.rst for hints about configuring
308 your e-mail client so that it sends your patch 308 your e-mail client so that it sends your patches untouched.
309 309
310 Respond to review comments 310 Respond to review comments
311 -------------------------- 311 --------------------------
312 312
313 Your patch will almost certainly get comments 313 Your patch will almost certainly get comments from reviewers on ways in
314 which the patch can be improved, in the form o 314 which the patch can be improved, in the form of a reply to your email. You must
315 respond to those comments; ignoring reviewers 315 respond to those comments; ignoring reviewers is a good way to get ignored in
316 return. You can simply reply to their emails t 316 return. You can simply reply to their emails to answer their comments. Review
317 comments or questions that do not lead to a co 317 comments or questions that do not lead to a code change should almost certainly
318 bring about a comment or changelog entry so th 318 bring about a comment or changelog entry so that the next reviewer better
319 understands what is going on. 319 understands what is going on.
320 320
321 Be sure to tell the reviewers what changes you 321 Be sure to tell the reviewers what changes you are making and to thank them
322 for their time. Code review is a tiring and t 322 for their time. Code review is a tiring and time-consuming process, and
323 reviewers sometimes get grumpy. Even in that 323 reviewers sometimes get grumpy. Even in that case, though, respond
324 politely and address the problems they have po !! 324 politely and address the problems they have pointed out.
325 version, add a ``patch changelog`` to the cove <<
326 explaining difference against previous submiss <<
327 :ref:`the_canonical_patch_format`). <<
328 Notify people that commented on your patch abo <<
329 the patches CC list. <<
330 325
331 See Documentation/process/email-clients.rst fo 326 See Documentation/process/email-clients.rst for recommendations on email
332 clients and mailing list etiquette. 327 clients and mailing list etiquette.
333 328
334 .. _interleaved_replies: <<
335 <<
336 Use trimmed interleaved replies in email discu <<
337 ---------------------------------------------- <<
338 Top-posting is strongly discouraged in Linux k <<
339 discussions. Interleaved (or "inline") replies <<
340 easier to follow. For more details see: <<
341 https://en.wikipedia.org/wiki/Posting_style#In <<
342 <<
343 As is frequently quoted on the mailing list:: <<
344 <<
345 A: http://en.wikipedia.org/wiki/Top_post <<
346 Q: Were do I find info about this thing call <<
347 A: Because it messes up the order in which p <<
348 Q: Why is top-posting such a bad thing? <<
349 A: Top-posting. <<
350 Q: What is the most annoying thing in e-mail <<
351 <<
352 Similarly, please trim all unneeded quotations <<
353 to your reply. This makes responses easier to <<
354 space. For more details see: http://daringfire <<
355 <<
356 A: No. <<
357 Q: Should I include quotations after my repl <<
358 <<
359 .. _resend_reminders: <<
360 329
361 Don't get discouraged - or impatient 330 Don't get discouraged - or impatient
362 ------------------------------------ 331 ------------------------------------
363 332
364 After you have submitted your change, be patie 333 After you have submitted your change, be patient and wait. Reviewers are
365 busy people and may not get to your patch righ 334 busy people and may not get to your patch right away.
366 335
367 Once upon a time, patches used to disappear in 336 Once upon a time, patches used to disappear into the void without comment,
368 but the development process works more smoothl 337 but the development process works more smoothly than that now. You should
369 receive comments within a few weeks (typically !! 338 receive comments within a week or so; if that does not happen, make sure
370 happen, make sure that you have sent your patc !! 339 that you have sent your patches to the right place. Wait for a minimum of
371 Wait for a minimum of one week before resubmit !! 340 one week before resubmitting or pinging reviewers - possibly longer during
372 - possibly longer during busy times like merge !! 341 busy times like merge windows.
373 342
374 It's also ok to resend the patch or the patch 343 It's also ok to resend the patch or the patch series after a couple of
375 weeks with the word "RESEND" added to the subj 344 weeks with the word "RESEND" added to the subject line::
376 345
377 [PATCH Vx RESEND] sub/sys: Condensed patch 346 [PATCH Vx RESEND] sub/sys: Condensed patch summary
378 347
379 Don't add "RESEND" when you are submitting a m 348 Don't add "RESEND" when you are submitting a modified version of your
380 patch or patch series - "RESEND" only applies 349 patch or patch series - "RESEND" only applies to resubmission of a
381 patch or patch series which have not been modi 350 patch or patch series which have not been modified in any way from the
382 previous submission. 351 previous submission.
383 352
384 353
385 Include PATCH in the subject 354 Include PATCH in the subject
386 ----------------------------- 355 -----------------------------
387 356
388 Due to high e-mail traffic to Linus, and to li 357 Due to high e-mail traffic to Linus, and to linux-kernel, it is common
389 convention to prefix your subject line with [P 358 convention to prefix your subject line with [PATCH]. This lets Linus
390 and other kernel developers more easily distin 359 and other kernel developers more easily distinguish patches from other
391 e-mail discussions. 360 e-mail discussions.
392 361
393 ``git send-email`` will do this for you automa 362 ``git send-email`` will do this for you automatically.
394 363
395 364
396 Sign your work - the Developer's Certificate o 365 Sign your work - the Developer's Certificate of Origin
397 ---------------------------------------------- 366 ------------------------------------------------------
398 367
399 To improve tracking of who did what, especiall 368 To improve tracking of who did what, especially with patches that can
400 percolate to their final resting place in the 369 percolate to their final resting place in the kernel through several
401 layers of maintainers, we've introduced a "sig 370 layers of maintainers, we've introduced a "sign-off" procedure on
402 patches that are being emailed around. 371 patches that are being emailed around.
403 372
404 The sign-off is a simple line at the end of th 373 The sign-off is a simple line at the end of the explanation for the
405 patch, which certifies that you wrote it or ot 374 patch, which certifies that you wrote it or otherwise have the right to
406 pass it on as an open-source patch. The rules 375 pass it on as an open-source patch. The rules are pretty simple: if you
407 can certify the below: 376 can certify the below:
408 377
409 Developer's Certificate of Origin 1.1 378 Developer's Certificate of Origin 1.1
410 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 379 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
411 380
412 By making a contribution to this project, I ce 381 By making a contribution to this project, I certify that:
413 382
414 (a) The contribution was created in wh 383 (a) The contribution was created in whole or in part by me and I
415 have the right to submit it under 384 have the right to submit it under the open source license
416 indicated in the file; or 385 indicated in the file; or
417 386
418 (b) The contribution is based upon pre 387 (b) The contribution is based upon previous work that, to the best
419 of my knowledge, is covered under 388 of my knowledge, is covered under an appropriate open source
420 license and I have the right under 389 license and I have the right under that license to submit that
421 work with modifications, whether c 390 work with modifications, whether created in whole or in part
422 by me, under the same open source 391 by me, under the same open source license (unless I am
423 permitted to submit under a differ 392 permitted to submit under a different license), as indicated
424 in the file; or 393 in the file; or
425 394
426 (c) The contribution was provided dire 395 (c) The contribution was provided directly to me by some other
427 person who certified (a), (b) or ( 396 person who certified (a), (b) or (c) and I have not modified
428 it. 397 it.
429 398
430 (d) I understand and agree that this p 399 (d) I understand and agree that this project and the contribution
431 are public and that a record of th 400 are public and that a record of the contribution (including all
432 personal information I submit with 401 personal information I submit with it, including my sign-off) is
433 maintained indefinitely and may be 402 maintained indefinitely and may be redistributed consistent with
434 this project or the open source li 403 this project or the open source license(s) involved.
435 404
436 then you just add a line saying:: 405 then you just add a line saying::
437 406
438 Signed-off-by: Random J Developer <rand 407 Signed-off-by: Random J Developer <random@developer.example.org>
439 408
440 using a known identity (sorry, no anonymous co !! 409 using your real name (sorry, no pseudonyms or anonymous contributions.)
441 This will be done for you automatically if you 410 This will be done for you automatically if you use ``git commit -s``.
442 Reverts should also include "Signed-off-by". ` 411 Reverts should also include "Signed-off-by". ``git revert -s`` does that
443 for you. 412 for you.
444 413
445 Some people also put extra tags at the end. T 414 Some people also put extra tags at the end. They'll just be ignored for
446 now, but you can do this to mark internal comp 415 now, but you can do this to mark internal company procedures or just
447 point out some special detail about the sign-o 416 point out some special detail about the sign-off.
448 417
449 Any further SoBs (Signed-off-by:'s) following 418 Any further SoBs (Signed-off-by:'s) following the author's SoB are from
450 people handling and transporting the patch, bu 419 people handling and transporting the patch, but were not involved in its
451 development. SoB chains should reflect the **r 420 development. SoB chains should reflect the **real** route a patch took
452 as it was propagated to the maintainers and ul 421 as it was propagated to the maintainers and ultimately to Linus, with
453 the first SoB entry signalling primary authors 422 the first SoB entry signalling primary authorship of a single author.
454 423
455 424
456 When to use Acked-by:, Cc:, and Co-developed-b 425 When to use Acked-by:, Cc:, and Co-developed-by:
457 ---------------------------------------------- 426 ------------------------------------------------
458 427
459 The Signed-off-by: tag indicates that the sign 428 The Signed-off-by: tag indicates that the signer was involved in the
460 development of the patch, or that he/she was i 429 development of the patch, or that he/she was in the patch's delivery path.
461 430
462 If a person was not directly involved in the p 431 If a person was not directly involved in the preparation or handling of a
463 patch but wishes to signify and record their a 432 patch but wishes to signify and record their approval of it then they can
464 ask to have an Acked-by: line added to the pat 433 ask to have an Acked-by: line added to the patch's changelog.
465 434
466 Acked-by: is often used by the maintainer of t 435 Acked-by: is often used by the maintainer of the affected code when that
467 maintainer neither contributed to nor forwarde 436 maintainer neither contributed to nor forwarded the patch.
468 437
469 Acked-by: is not as formal as Signed-off-by:. 438 Acked-by: is not as formal as Signed-off-by:. It is a record that the acker
470 has at least reviewed the patch and has indica 439 has at least reviewed the patch and has indicated acceptance. Hence patch
471 mergers will sometimes manually convert an ack 440 mergers will sometimes manually convert an acker's "yep, looks good to me"
472 into an Acked-by: (but note that it is usually 441 into an Acked-by: (but note that it is usually better to ask for an
473 explicit ack). 442 explicit ack).
474 443
475 Acked-by: does not necessarily indicate acknow 444 Acked-by: does not necessarily indicate acknowledgement of the entire patch.
476 For example, if a patch affects multiple subsy 445 For example, if a patch affects multiple subsystems and has an Acked-by: from
477 one subsystem maintainer then this usually ind 446 one subsystem maintainer then this usually indicates acknowledgement of just
478 the part which affects that maintainer's code. 447 the part which affects that maintainer's code. Judgement should be used here.
479 When in doubt people should refer to the origi 448 When in doubt people should refer to the original discussion in the mailing
480 list archives. 449 list archives.
481 450
482 If a person has had the opportunity to comment 451 If a person has had the opportunity to comment on a patch, but has not
483 provided such comments, you may optionally add 452 provided such comments, you may optionally add a ``Cc:`` tag to the patch.
484 This is the only tag which might be added with 453 This is the only tag which might be added without an explicit action by the
485 person it names - but it should indicate that 454 person it names - but it should indicate that this person was copied on the
486 patch. This tag documents that potentially in 455 patch. This tag documents that potentially interested parties
487 have been included in the discussion. 456 have been included in the discussion.
488 457
489 Co-developed-by: states that the patch was co- 458 Co-developed-by: states that the patch was co-created by multiple developers;
490 it is used to give attribution to co-authors ( 459 it is used to give attribution to co-authors (in addition to the author
491 attributed by the From: tag) when several peop 460 attributed by the From: tag) when several people work on a single patch. Since
492 Co-developed-by: denotes authorship, every Co- 461 Co-developed-by: denotes authorship, every Co-developed-by: must be immediately
493 followed by a Signed-off-by: of the associated 462 followed by a Signed-off-by: of the associated co-author. Standard sign-off
494 procedure applies, i.e. the ordering of Signed 463 procedure applies, i.e. the ordering of Signed-off-by: tags should reflect the
495 chronological history of the patch insofar as 464 chronological history of the patch insofar as possible, regardless of whether
496 the author is attributed via From: or Co-devel 465 the author is attributed via From: or Co-developed-by:. Notably, the last
497 Signed-off-by: must always be that of the deve 466 Signed-off-by: must always be that of the developer submitting the patch.
498 467
499 Note, the From: tag is optional when the From: 468 Note, the From: tag is optional when the From: author is also the person (and
500 email) listed in the From: line of the email h 469 email) listed in the From: line of the email header.
501 470
502 Example of a patch submitted by the From: auth 471 Example of a patch submitted by the From: author::
503 472
504 <changelog> 473 <changelog>
505 474
506 Co-developed-by: First Co-Author <first 475 Co-developed-by: First Co-Author <first@coauthor.example.org>
507 Signed-off-by: First Co-Author <first@c 476 Signed-off-by: First Co-Author <first@coauthor.example.org>
508 Co-developed-by: Second Co-Author <seco 477 Co-developed-by: Second Co-Author <second@coauthor.example.org>
509 Signed-off-by: Second Co-Author <second 478 Signed-off-by: Second Co-Author <second@coauthor.example.org>
510 Signed-off-by: From Author <from@author 479 Signed-off-by: From Author <from@author.example.org>
511 480
512 Example of a patch submitted by a Co-developed 481 Example of a patch submitted by a Co-developed-by: author::
513 482
514 From: From Author <from@author.example. 483 From: From Author <from@author.example.org>
515 484
516 <changelog> 485 <changelog>
517 486
518 Co-developed-by: Random Co-Author <rand 487 Co-developed-by: Random Co-Author <random@coauthor.example.org>
519 Signed-off-by: Random Co-Author <random 488 Signed-off-by: Random Co-Author <random@coauthor.example.org>
520 Signed-off-by: From Author <from@author 489 Signed-off-by: From Author <from@author.example.org>
521 Co-developed-by: Submitting Co-Author < 490 Co-developed-by: Submitting Co-Author <sub@coauthor.example.org>
522 Signed-off-by: Submitting Co-Author <su 491 Signed-off-by: Submitting Co-Author <sub@coauthor.example.org>
523 492
524 493
525 Using Reported-by:, Tested-by:, Reviewed-by:, 494 Using Reported-by:, Tested-by:, Reviewed-by:, Suggested-by: and Fixes:
526 ---------------------------------------------- 495 ----------------------------------------------------------------------
527 496
528 The Reported-by tag gives credit to people who 497 The Reported-by tag gives credit to people who find bugs and report them and it
529 hopefully inspires them to help us again in th !! 498 hopefully inspires them to help us again in the future. Please note that if
530 bugs; please do not use it to credit feature r !! 499 the bug was reported in private, then ask for permission first before using the
531 followed by a Closes: tag pointing to the repo !! 500 Reported-by tag.
532 available on the web. The Link: tag can be use <<
533 fixes a part of the issue(s) being reported. P <<
534 reported in private, then ask for permission f <<
535 tag. <<
536 501
537 A Tested-by: tag indicates that the patch has 502 A Tested-by: tag indicates that the patch has been successfully tested (in
538 some environment) by the person named. This t 503 some environment) by the person named. This tag informs maintainers that
539 some testing has been performed, provides a me 504 some testing has been performed, provides a means to locate testers for
540 future patches, and ensures credit for the tes 505 future patches, and ensures credit for the testers.
541 506
542 Reviewed-by:, instead, indicates that the patc 507 Reviewed-by:, instead, indicates that the patch has been reviewed and found
543 acceptable according to the Reviewer's Stateme 508 acceptable according to the Reviewer's Statement:
544 509
545 Reviewer's statement of oversight 510 Reviewer's statement of oversight
546 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 511 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
547 512
548 By offering my Reviewed-by: tag, I state that: 513 By offering my Reviewed-by: tag, I state that:
549 514
550 (a) I have carried out a technical re 515 (a) I have carried out a technical review of this patch to
551 evaluate its appropriateness and 516 evaluate its appropriateness and readiness for inclusion into
552 the mainline kernel. 517 the mainline kernel.
553 518
554 (b) Any problems, concerns, or questi 519 (b) Any problems, concerns, or questions relating to the patch
555 have been communicated back to th 520 have been communicated back to the submitter. I am satisfied
556 with the submitter's response to 521 with the submitter's response to my comments.
557 522
558 (c) While there may be things that co 523 (c) While there may be things that could be improved with this
559 submission, I believe that it is, 524 submission, I believe that it is, at this time, (1) a
560 worthwhile modification to the ke 525 worthwhile modification to the kernel, and (2) free of known
561 issues which would argue against 526 issues which would argue against its inclusion.
562 527
563 (d) While I have reviewed the patch a 528 (d) While I have reviewed the patch and believe it to be sound, I
564 do not (unless explicitly stated 529 do not (unless explicitly stated elsewhere) make any
565 warranties or guarantees that it 530 warranties or guarantees that it will achieve its stated
566 purpose or function properly in a 531 purpose or function properly in any given situation.
567 532
568 A Reviewed-by tag is a statement of opinion th 533 A Reviewed-by tag is a statement of opinion that the patch is an
569 appropriate modification of the kernel without 534 appropriate modification of the kernel without any remaining serious
570 technical issues. Any interested reviewer (wh 535 technical issues. Any interested reviewer (who has done the work) can
571 offer a Reviewed-by tag for a patch. This tag 536 offer a Reviewed-by tag for a patch. This tag serves to give credit to
572 reviewers and to inform maintainers of the deg 537 reviewers and to inform maintainers of the degree of review which has been
573 done on the patch. Reviewed-by: tags, when su 538 done on the patch. Reviewed-by: tags, when supplied by reviewers known to
574 understand the subject area and to perform tho 539 understand the subject area and to perform thorough reviews, will normally
575 increase the likelihood of your patch getting 540 increase the likelihood of your patch getting into the kernel.
576 541
577 Both Tested-by and Reviewed-by tags, once rece 542 Both Tested-by and Reviewed-by tags, once received on mailing list from tester
578 or reviewer, should be added by author to the 543 or reviewer, should be added by author to the applicable patches when sending
579 next versions. However if the patch has chang 544 next versions. However if the patch has changed substantially in following
580 version, these tags might not be applicable an 545 version, these tags might not be applicable anymore and thus should be removed.
581 Usually removal of someone's Tested-by or Revi 546 Usually removal of someone's Tested-by or Reviewed-by tags should be mentioned
582 in the patch changelog (after the '---' separa 547 in the patch changelog (after the '---' separator).
583 548
584 A Suggested-by: tag indicates that the patch i 549 A Suggested-by: tag indicates that the patch idea is suggested by the person
585 named and ensures credit to the person for the 550 named and ensures credit to the person for the idea. Please note that this
586 tag should not be added without the reporter's 551 tag should not be added without the reporter's permission, especially if the
587 idea was not posted in a public forum. That sa 552 idea was not posted in a public forum. That said, if we diligently credit our
588 idea reporters, they will, hopefully, be inspi 553 idea reporters, they will, hopefully, be inspired to help us again in the
589 future. 554 future.
590 555
591 A Fixes: tag indicates that the patch fixes an 556 A Fixes: tag indicates that the patch fixes an issue in a previous commit. It
592 is used to make it easy to determine where a b 557 is used to make it easy to determine where a bug originated, which can help
593 review a bug fix. This tag also assists the st 558 review a bug fix. This tag also assists the stable kernel team in determining
594 which stable kernel versions should receive yo 559 which stable kernel versions should receive your fix. This is the preferred
595 method for indicating a bug fixed by the patch 560 method for indicating a bug fixed by the patch. See :ref:`describe_changes`
596 for more details. 561 for more details.
597 562
598 Note: Attaching a Fixes: tag does not subvert 563 Note: Attaching a Fixes: tag does not subvert the stable kernel rules
599 process nor the requirement to Cc: stable@vger 564 process nor the requirement to Cc: stable@vger.kernel.org on all stable
600 patch candidates. For more information, please 565 patch candidates. For more information, please read
601 Documentation/process/stable-kernel-rules.rst. 566 Documentation/process/stable-kernel-rules.rst.
602 567
603 .. _the_canonical_patch_format: 568 .. _the_canonical_patch_format:
604 569
605 The canonical patch format 570 The canonical patch format
606 -------------------------- 571 --------------------------
607 572
608 This section describes how the patch itself sh 573 This section describes how the patch itself should be formatted. Note
609 that, if you have your patches stored in a ``g 574 that, if you have your patches stored in a ``git`` repository, proper patch
610 formatting can be had with ``git format-patch` 575 formatting can be had with ``git format-patch``. The tools cannot create
611 the necessary text, though, so read the instru 576 the necessary text, though, so read the instructions below anyway.
612 577
613 The canonical patch subject line is:: 578 The canonical patch subject line is::
614 579
615 Subject: [PATCH 001/123] subsystem: summar 580 Subject: [PATCH 001/123] subsystem: summary phrase
616 581
617 The canonical patch message body contains the 582 The canonical patch message body contains the following:
618 583
619 - A ``from`` line specifying the patch autho 584 - A ``from`` line specifying the patch author, followed by an empty
620 line (only needed if the person sending th 585 line (only needed if the person sending the patch is not the author).
621 586
622 - The body of the explanation, line wrapped 587 - The body of the explanation, line wrapped at 75 columns, which will
623 be copied to the permanent changelog to de 588 be copied to the permanent changelog to describe this patch.
624 589
625 - An empty line. 590 - An empty line.
626 591
627 - The ``Signed-off-by:`` lines, described ab 592 - The ``Signed-off-by:`` lines, described above, which will
628 also go in the changelog. 593 also go in the changelog.
629 594
630 - A marker line containing simply ``---``. 595 - A marker line containing simply ``---``.
631 596
632 - Any additional comments not suitable for t 597 - Any additional comments not suitable for the changelog.
633 598
634 - The actual patch (``diff`` output). 599 - The actual patch (``diff`` output).
635 600
636 The Subject line format makes it very easy to 601 The Subject line format makes it very easy to sort the emails
637 alphabetically by subject line - pretty much a 602 alphabetically by subject line - pretty much any email reader will
638 support that - since because the sequence numb 603 support that - since because the sequence number is zero-padded,
639 the numerical and alphabetic sort is the same. 604 the numerical and alphabetic sort is the same.
640 605
641 The ``subsystem`` in the email's Subject shoul 606 The ``subsystem`` in the email's Subject should identify which
642 area or subsystem of the kernel is being patch 607 area or subsystem of the kernel is being patched.
643 608
644 The ``summary phrase`` in the email's Subject 609 The ``summary phrase`` in the email's Subject should concisely
645 describe the patch which that email contains. 610 describe the patch which that email contains. The ``summary
646 phrase`` should not be a filename. Do not use 611 phrase`` should not be a filename. Do not use the same ``summary
647 phrase`` for every patch in a whole patch seri 612 phrase`` for every patch in a whole patch series (where a ``patch
648 series`` is an ordered sequence of multiple, r 613 series`` is an ordered sequence of multiple, related patches).
649 614
650 Bear in mind that the ``summary phrase`` of yo 615 Bear in mind that the ``summary phrase`` of your email becomes a
651 globally-unique identifier for that patch. It 616 globally-unique identifier for that patch. It propagates all the way
652 into the ``git`` changelog. The ``summary phr 617 into the ``git`` changelog. The ``summary phrase`` may later be used in
653 developer discussions which refer to the patch 618 developer discussions which refer to the patch. People will want to
654 google for the ``summary phrase`` to read disc 619 google for the ``summary phrase`` to read discussion regarding that
655 patch. It will also be the only thing that pe 620 patch. It will also be the only thing that people may quickly see
656 when, two or three months later, they are goin 621 when, two or three months later, they are going through perhaps
657 thousands of patches using tools such as ``git 622 thousands of patches using tools such as ``gitk`` or ``git log
658 --oneline``. 623 --oneline``.
659 624
660 For these reasons, the ``summary`` must be no 625 For these reasons, the ``summary`` must be no more than 70-75
661 characters, and it must describe both what the 626 characters, and it must describe both what the patch changes, as well
662 as why the patch might be necessary. It is ch 627 as why the patch might be necessary. It is challenging to be both
663 succinct and descriptive, but that is what a w 628 succinct and descriptive, but that is what a well-written summary
664 should do. 629 should do.
665 630
666 The ``summary phrase`` may be prefixed by tags 631 The ``summary phrase`` may be prefixed by tags enclosed in square
667 brackets: "Subject: [PATCH <tag>...] <summary 632 brackets: "Subject: [PATCH <tag>...] <summary phrase>". The tags are
668 not considered part of the summary phrase, but 633 not considered part of the summary phrase, but describe how the patch
669 should be treated. Common tags might include 634 should be treated. Common tags might include a version descriptor if
670 the multiple versions of the patch have been s 635 the multiple versions of the patch have been sent out in response to
671 comments (i.e., "v1, v2, v3"), or "RFC" to ind 636 comments (i.e., "v1, v2, v3"), or "RFC" to indicate a request for
672 comments. 637 comments.
673 638
674 If there are four patches in a patch series th 639 If there are four patches in a patch series the individual patches may
675 be numbered like this: 1/4, 2/4, 3/4, 4/4. Thi 640 be numbered like this: 1/4, 2/4, 3/4, 4/4. This assures that developers
676 understand the order in which the patches shou 641 understand the order in which the patches should be applied and that
677 they have reviewed or applied all of the patch 642 they have reviewed or applied all of the patches in the patch series.
678 643
679 Here are some good example Subjects:: 644 Here are some good example Subjects::
680 645
681 Subject: [PATCH 2/5] ext2: improve scalabi 646 Subject: [PATCH 2/5] ext2: improve scalability of bitmap searching
682 Subject: [PATCH v2 01/27] x86: fix eflags 647 Subject: [PATCH v2 01/27] x86: fix eflags tracking
683 Subject: [PATCH v2] sub/sys: Condensed pat 648 Subject: [PATCH v2] sub/sys: Condensed patch summary
684 Subject: [PATCH v2 M/N] sub/sys: Condensed 649 Subject: [PATCH v2 M/N] sub/sys: Condensed patch summary
685 650
686 The ``from`` line must be the very first line 651 The ``from`` line must be the very first line in the message body,
687 and has the form: 652 and has the form:
688 653
689 From: Patch Author <author@example.com> 654 From: Patch Author <author@example.com>
690 655
691 The ``from`` line specifies who will be credit 656 The ``from`` line specifies who will be credited as the author of the
692 patch in the permanent changelog. If the ``fr 657 patch in the permanent changelog. If the ``from`` line is missing,
693 then the ``From:`` line from the email header 658 then the ``From:`` line from the email header will be used to determine
694 the patch author in the changelog. 659 the patch author in the changelog.
695 660
696 The explanation body will be committed to the 661 The explanation body will be committed to the permanent source
697 changelog, so should make sense to a competent 662 changelog, so should make sense to a competent reader who has long since
698 forgotten the immediate details of the discuss 663 forgotten the immediate details of the discussion that might have led to
699 this patch. Including symptoms of the failure 664 this patch. Including symptoms of the failure which the patch addresses
700 (kernel log messages, oops messages, etc.) are 665 (kernel log messages, oops messages, etc.) are especially useful for
701 people who might be searching the commit logs 666 people who might be searching the commit logs looking for the applicable
702 patch. The text should be written in such deta 667 patch. The text should be written in such detail so that when read
703 weeks, months or even years later, it can give 668 weeks, months or even years later, it can give the reader the needed
704 details to grasp the reasoning for **why** the 669 details to grasp the reasoning for **why** the patch was created.
705 670
706 If a patch fixes a compile failure, it may not 671 If a patch fixes a compile failure, it may not be necessary to include
707 _all_ of the compile failures; just enough tha 672 _all_ of the compile failures; just enough that it is likely that
708 someone searching for the patch can find it. A 673 someone searching for the patch can find it. As in the ``summary
709 phrase``, it is important to be both succinct 674 phrase``, it is important to be both succinct as well as descriptive.
710 675
711 The ``---`` marker line serves the essential p 676 The ``---`` marker line serves the essential purpose of marking for
712 patch handling tools where the changelog messa 677 patch handling tools where the changelog message ends.
713 678
714 One good use for the additional comments after 679 One good use for the additional comments after the ``---`` marker is
715 for a ``diffstat``, to show what files have ch 680 for a ``diffstat``, to show what files have changed, and the number of
716 inserted and deleted lines per file. A ``diffs 681 inserted and deleted lines per file. A ``diffstat`` is especially useful
717 on bigger patches. If you are going to include 682 on bigger patches. If you are going to include a ``diffstat`` after the
718 ``---`` marker, please use ``diffstat`` option 683 ``---`` marker, please use ``diffstat`` options ``-p 1 -w 70`` so that
719 filenames are listed from the top of the kerne 684 filenames are listed from the top of the kernel source tree and don't
720 use too much horizontal space (easily fit in 8 685 use too much horizontal space (easily fit in 80 columns, maybe with some
721 indentation). (``git`` generates appropriate d 686 indentation). (``git`` generates appropriate diffstats by default.)
722 687
723 Other comments relevant only to the moment or 688 Other comments relevant only to the moment or the maintainer, not
724 suitable for the permanent changelog, should a 689 suitable for the permanent changelog, should also go here. A good
725 example of such comments might be ``patch chan 690 example of such comments might be ``patch changelogs`` which describe
726 what has changed between the v1 and v2 version 691 what has changed between the v1 and v2 version of the patch.
727 692
728 Please put this information **after** the ``-- 693 Please put this information **after** the ``---`` line which separates
729 the changelog from the rest of the patch. The 694 the changelog from the rest of the patch. The version information is
730 not part of the changelog which gets committed 695 not part of the changelog which gets committed to the git tree. It is
731 additional information for the reviewers. If i 696 additional information for the reviewers. If it's placed above the
732 commit tags, it needs manual interaction to re 697 commit tags, it needs manual interaction to remove it. If it is below
733 the separator line, it gets automatically stri 698 the separator line, it gets automatically stripped off when applying the
734 patch:: 699 patch::
735 700
736 <commit message> 701 <commit message>
737 ... 702 ...
738 Signed-off-by: Author <author@mail> 703 Signed-off-by: Author <author@mail>
739 --- 704 ---
740 V2 -> V3: Removed redundant helper function 705 V2 -> V3: Removed redundant helper function
741 V1 -> V2: Cleaned up coding style and addres 706 V1 -> V2: Cleaned up coding style and addressed review comments
742 707
743 path/to/file | 5+++-- 708 path/to/file | 5+++--
744 ... 709 ...
745 710
746 See more details on the proper patch format in 711 See more details on the proper patch format in the following
747 references. 712 references.
748 713
749 .. _backtraces: !! 714 Backtraces in commit mesages
750 !! 715 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
751 Backtraces in commit messages <<
752 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ <<
753 716
754 Backtraces help document the call chain leadin 717 Backtraces help document the call chain leading to a problem. However,
755 not all backtraces are helpful. For example, e 718 not all backtraces are helpful. For example, early boot call chains are
756 unique and obvious. Copying the full dmesg out 719 unique and obvious. Copying the full dmesg output verbatim, however,
757 adds distracting information like timestamps, 720 adds distracting information like timestamps, module lists, register and
758 stack dumps. 721 stack dumps.
759 722
760 Therefore, the most useful backtraces should d 723 Therefore, the most useful backtraces should distill the relevant
761 information from the dump, which makes it easi 724 information from the dump, which makes it easier to focus on the real
762 issue. Here is an example of a well-trimmed ba 725 issue. Here is an example of a well-trimmed backtrace::
763 726
764 unchecked MSR access error: WRMSR to 0xd51 ( 727 unchecked MSR access error: WRMSR to 0xd51 (tried to write 0x0000000000000064)
765 at rIP: 0xffffffffae059994 (native_write_msr 728 at rIP: 0xffffffffae059994 (native_write_msr+0x4/0x20)
766 Call Trace: 729 Call Trace:
767 mba_wrmsr 730 mba_wrmsr
768 update_domains 731 update_domains
769 rdtgroup_mkdir 732 rdtgroup_mkdir
770 733
771 .. _explicit_in_reply_to: 734 .. _explicit_in_reply_to:
772 735
773 Explicit In-Reply-To headers 736 Explicit In-Reply-To headers
774 ---------------------------- 737 ----------------------------
775 738
776 It can be helpful to manually add In-Reply-To: 739 It can be helpful to manually add In-Reply-To: headers to a patch
777 (e.g., when using ``git send-email``) to assoc 740 (e.g., when using ``git send-email``) to associate the patch with
778 previous relevant discussion, e.g. to link a b 741 previous relevant discussion, e.g. to link a bug fix to the email with
779 the bug report. However, for a multi-patch se 742 the bug report. However, for a multi-patch series, it is generally
780 best to avoid using In-Reply-To: to link to ol 743 best to avoid using In-Reply-To: to link to older versions of the
781 series. This way multiple versions of the pat 744 series. This way multiple versions of the patch don't become an
782 unmanageable forest of references in email cli 745 unmanageable forest of references in email clients. If a link is
783 helpful, you can use the https://lore.kernel.o !! 746 helpful, you can use the https://lkml.kernel.org/ redirector (e.g., in
784 the cover email text) to link to an earlier ve 747 the cover email text) to link to an earlier version of the patch series.
785 748
786 749
787 Providing base tree information 750 Providing base tree information
788 ------------------------------- 751 -------------------------------
789 752
790 When other developers receive your patches and 753 When other developers receive your patches and start the review process,
791 it is absolutely necessary for them to know wh !! 754 it is often useful for them to know where in the tree history they
792 commit/branch your work applies on, considerin !! 755 should place your work. This is particularly useful for automated CI
793 maintainer trees present nowadays. Note again !! 756 processes that attempt to run a series of tests in order to establish
794 MAINTAINERS file explained above. !! 757 the quality of your submission before the maintainer starts the review.
795 <<
796 This is even more important for automated CI p <<
797 run a series of tests in order to establish th <<
798 submission before the maintainer starts the re <<
799 758
800 If you are using ``git format-patch`` to gener 759 If you are using ``git format-patch`` to generate your patches, you can
801 automatically include the base tree informatio 760 automatically include the base tree information in your submission by
802 using the ``--base`` flag. The easiest and mos 761 using the ``--base`` flag. The easiest and most convenient way to use
803 this option is with topical branches:: 762 this option is with topical branches::
804 763
805 $ git checkout -t -b my-topical-branch mas 764 $ git checkout -t -b my-topical-branch master
806 Branch 'my-topical-branch' set up to track 765 Branch 'my-topical-branch' set up to track local branch 'master'.
807 Switched to a new branch 'my-topical-branc 766 Switched to a new branch 'my-topical-branch'
808 767
809 [perform your edits and commits] 768 [perform your edits and commits]
810 769
811 $ git format-patch --base=auto --cover-let 770 $ git format-patch --base=auto --cover-letter -o outgoing/ master
812 outgoing/0000-cover-letter.patch 771 outgoing/0000-cover-letter.patch
813 outgoing/0001-First-Commit.patch 772 outgoing/0001-First-Commit.patch
814 outgoing/... 773 outgoing/...
815 774
816 When you open ``outgoing/0000-cover-letter.pat 775 When you open ``outgoing/0000-cover-letter.patch`` for editing, you will
817 notice that it will have the ``base-commit:`` 776 notice that it will have the ``base-commit:`` trailer at the very
818 bottom, which provides the reviewer and the CI 777 bottom, which provides the reviewer and the CI tools enough information
819 to properly perform ``git am`` without worryin 778 to properly perform ``git am`` without worrying about conflicts::
820 779
821 $ git checkout -b patch-review [base-commi 780 $ git checkout -b patch-review [base-commit-id]
822 Switched to a new branch 'patch-review' 781 Switched to a new branch 'patch-review'
823 $ git am patches.mbox 782 $ git am patches.mbox
824 Applying: First Commit 783 Applying: First Commit
825 Applying: ... 784 Applying: ...
826 785
827 Please see ``man git-format-patch`` for more i 786 Please see ``man git-format-patch`` for more information about this
828 option. 787 option.
829 788
830 .. note:: 789 .. note::
831 790
832 The ``--base`` feature was introduced in g 791 The ``--base`` feature was introduced in git version 2.9.0.
833 792
834 If you are not using git to format your patche 793 If you are not using git to format your patches, you can still include
835 the same ``base-commit`` trailer to indicate t 794 the same ``base-commit`` trailer to indicate the commit hash of the tree
836 on which your work is based. You should add it 795 on which your work is based. You should add it either in the cover
837 letter or in the first patch of the series and 796 letter or in the first patch of the series and it should be placed
838 either below the ``---`` line or at the very b 797 either below the ``---`` line or at the very bottom of all other
839 content, right before your email signature. 798 content, right before your email signature.
840 799
841 Make sure that base commit is in an official m <<
842 and not in some internal, accessible only to y <<
843 would be worthless. <<
844 <<
845 Tooling <<
846 ------- <<
847 <<
848 Many of the technical aspects of this process <<
849 b4, documented at <https://b4.docs.kernel.org/ <<
850 help with things like tracking dependencies, r <<
851 with formatting and sending mails. <<
852 800
853 References 801 References
854 ---------- 802 ----------
855 803
856 Andrew Morton, "The perfect patch" (tpp). 804 Andrew Morton, "The perfect patch" (tpp).
857 <https://www.ozlabs.org/~akpm/stuff/tpp.txt> 805 <https://www.ozlabs.org/~akpm/stuff/tpp.txt>
858 806
859 Jeff Garzik, "Linux kernel patch submission fo 807 Jeff Garzik, "Linux kernel patch submission format".
860 <https://web.archive.org/web/20180829112450/ 808 <https://web.archive.org/web/20180829112450/http://linux.yyz.us/patch-format.html>
861 809
862 Greg Kroah-Hartman, "How to piss off a kernel 810 Greg Kroah-Hartman, "How to piss off a kernel subsystem maintainer".
863 <http://www.kroah.com/log/linux/maintainer.h 811 <http://www.kroah.com/log/linux/maintainer.html>
864 812
865 <http://www.kroah.com/log/linux/maintainer-0 813 <http://www.kroah.com/log/linux/maintainer-02.html>
866 814
867 <http://www.kroah.com/log/linux/maintainer-0 815 <http://www.kroah.com/log/linux/maintainer-03.html>
868 816
869 <http://www.kroah.com/log/linux/maintainer-0 817 <http://www.kroah.com/log/linux/maintainer-04.html>
870 818
871 <http://www.kroah.com/log/linux/maintainer-0 819 <http://www.kroah.com/log/linux/maintainer-05.html>
872 820
873 <http://www.kroah.com/log/linux/maintainer-0 821 <http://www.kroah.com/log/linux/maintainer-06.html>
>> 822
>> 823 NO!!!! No more huge patch bombs to linux-kernel@vger.kernel.org people!
>> 824 <https://lore.kernel.org/r/20050711.125305.08322243.davem@davemloft.net">https://lore.kernel.org/r/20050711.125305.08322243.davem@davemloft.net>
874 825
875 Kernel Documentation/process/coding-style.rst 826 Kernel Documentation/process/coding-style.rst
876 827
877 Linus Torvalds's mail on the canonical patch f 828 Linus Torvalds's mail on the canonical patch format:
878 <https://lore.kernel.org/r/Pine.LNX.4.58.0504 829 <https://lore.kernel.org/r/Pine.LNX.4.58.0504071023190.28951@ppc970.osdl.org">https://lore.kernel.org/r/Pine.LNX.4.58.0504071023190.28951@ppc970.osdl.org>
879 830
880 Andi Kleen, "On submitting kernel patches" 831 Andi Kleen, "On submitting kernel patches"
881 Some strategies to get difficult or controve 832 Some strategies to get difficult or controversial changes in.
882 833
883 http://halobates.de/on-submitting-patches.pd 834 http://halobates.de/on-submitting-patches.pdf
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