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.
16 For device tree binding patches, read 16 For device tree binding patches, read
17 Documentation/devicetree/bindings/submitting-p 17 Documentation/devicetree/bindings/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 24 Some subsystems and maintainer trees have additional information about
25 their workflow and expectations, see 25 their workflow and expectations, see
26 :ref:`Documentation/process/maintainer-handboo 26 :ref:`Documentation/process/maintainer-handbooks.rst <maintainer_handbooks_main>`.
27 27
28 Obtain a current source tree 28 Obtain a current source tree
29 ---------------------------- 29 ----------------------------
30 30
31 If you do not have a repository with the curre 31 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 32 ``git`` to obtain one. You'll want to start with the mainline repository,
33 which can be grabbed with:: 33 which can be grabbed with::
34 34
35 git clone git://git.kernel.org/pub/scm/linux 35 git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
36 36
37 Note, however, that you may not want to develo 37 Note, however, that you may not want to develop against the mainline tree
38 directly. Most subsystem maintainers run thei 38 directly. Most subsystem maintainers run their own trees and want to see
39 patches prepared against those trees. See the 39 patches prepared against those trees. See the **T:** entry for the subsystem
40 in the MAINTAINERS file to find that tree, or 40 in the MAINTAINERS file to find that tree, or simply ask the maintainer if
41 the tree is not listed there. 41 the tree is not listed there.
42 42
43 .. _describe_changes: 43 .. _describe_changes:
44 44
45 Describe your changes 45 Describe your changes
46 --------------------- 46 ---------------------
47 47
48 Describe your problem. Whether your patch is 48 Describe your problem. Whether your patch is a one-line bug fix or
49 5000 lines of a new feature, there must be an 49 5000 lines of a new feature, there must be an underlying problem that
50 motivated you to do this work. Convince the r 50 motivated you to do this work. Convince the reviewer that there is a
51 problem worth fixing and that it makes sense f 51 problem worth fixing and that it makes sense for them to read past the
52 first paragraph. 52 first paragraph.
53 53
54 Describe user-visible impact. Straight up cra 54 Describe user-visible impact. Straight up crashes and lockups are
55 pretty convincing, but not all bugs are that b 55 pretty convincing, but not all bugs are that blatant. Even if the
56 problem was spotted during code review, descri 56 problem was spotted during code review, describe the impact you think
57 it can have on users. Keep in mind that the m 57 it can have on users. Keep in mind that the majority of Linux
58 installations run kernels from secondary stabl 58 installations run kernels from secondary stable trees or
59 vendor/product-specific trees that cherry-pick 59 vendor/product-specific trees that cherry-pick only specific patches
60 from upstream, so include anything that could 60 from upstream, so include anything that could help route your change
61 downstream: provoking circumstances, excerpts 61 downstream: provoking circumstances, excerpts from dmesg, crash
62 descriptions, performance regressions, latency 62 descriptions, performance regressions, latency spikes, lockups, etc.
63 63
64 Quantify optimizations and trade-offs. If you 64 Quantify optimizations and trade-offs. If you claim improvements in
65 performance, memory consumption, stack footpri 65 performance, memory consumption, stack footprint, or binary size,
66 include numbers that back them up. But also d 66 include numbers that back them up. But also describe non-obvious
67 costs. Optimizations usually aren't free but 67 costs. Optimizations usually aren't free but trade-offs between CPU,
68 memory, and readability; or, when it comes to 68 memory, and readability; or, when it comes to heuristics, between
69 different workloads. Describe the expected do 69 different workloads. Describe the expected downsides of your
70 optimization so that the reviewer can weigh co 70 optimization so that the reviewer can weigh costs against benefits.
71 71
72 Once the problem is established, describe what 72 Once the problem is established, describe what you are actually doing
73 about it in technical detail. It's important 73 about it in technical detail. It's important to describe the change
74 in plain English for the reviewer to verify th 74 in plain English for the reviewer to verify that the code is behaving
75 as you intend it to. 75 as you intend it to.
76 76
77 The maintainer will thank you if you write you 77 The maintainer will thank you if you write your patch description in a
78 form which can be easily pulled into Linux's s 78 form which can be easily pulled into Linux's source code management
79 system, ``git``, as a "commit log". See :ref: 79 system, ``git``, as a "commit log". See :ref:`the_canonical_patch_format`.
80 80
81 Solve only one problem per patch. If your des 81 Solve only one problem per patch. If your description starts to get
82 long, that's a sign that you probably need to 82 long, that's a sign that you probably need to split up your patch.
83 See :ref:`split_changes`. 83 See :ref:`split_changes`.
84 84
85 When you submit or resubmit a patch or patch s 85 When you submit or resubmit a patch or patch series, include the
86 complete patch description and justification f 86 complete patch description and justification for it. Don't just
87 say that this is version N of the patch (serie 87 say that this is version N of the patch (series). Don't expect the
88 subsystem maintainer to refer back to earlier 88 subsystem maintainer to refer back to earlier patch versions or referenced
89 URLs to find the patch description and put tha 89 URLs to find the patch description and put that into the patch.
90 I.e., the patch (series) and its description s 90 I.e., the patch (series) and its description should be self-contained.
91 This benefits both the maintainers and reviewe 91 This benefits both the maintainers and reviewers. Some reviewers
92 probably didn't even receive earlier versions 92 probably didn't even receive earlier versions of the patch.
93 93
94 Describe your changes in imperative mood, e.g. 94 Describe your changes in imperative mood, e.g. "make xyzzy do frotz"
95 instead of "[This patch] makes xyzzy do frotz" 95 instead of "[This patch] makes xyzzy do frotz" or "[I] changed xyzzy
96 to do frotz", as if you are giving orders to t 96 to do frotz", as if you are giving orders to the codebase to change
97 its behaviour. 97 its behaviour.
98 98
99 If you want to refer to a specific commit, don 99 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 100 SHA-1 ID of the commit. Please also include the oneline summary of
101 the commit, to make it easier for reviewers to 101 the commit, to make it easier for reviewers to know what it is about.
102 Example:: 102 Example::
103 103
104 Commit e21d2170f36602ae2708 ("video: r 104 Commit e21d2170f36602ae2708 ("video: remove unnecessary
105 platform_set_drvdata()") removed the u 105 platform_set_drvdata()") removed the unnecessary
106 platform_set_drvdata(), but left the v 106 platform_set_drvdata(), but left the variable "dev" unused,
107 delete it. 107 delete it.
108 108
109 You should also be sure to use at least the fi 109 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* 110 SHA-1 ID. The kernel repository holds a *lot* of objects, making
111 collisions with shorter IDs a real possibility 111 collisions with shorter IDs a real possibility. Bear in mind that, even if
112 there is no collision with your six-character 112 there is no collision with your six-character ID now, that condition may
113 change five years from now. 113 change five years from now.
114 114
115 If related discussions or any other background 115 If related discussions or any other background information behind the change
116 can be found on the web, add 'Link:' tags poin 116 can be found on the web, add 'Link:' tags pointing to it. If the patch is a
117 result of some earlier mailing list discussion 117 result of some earlier mailing list discussions or something documented on the
118 web, point to it. 118 web, point to it.
119 119
120 When linking to mailing list archives, prefera 120 When linking to mailing list archives, preferably use the lore.kernel.org
121 message archiver service. To create the link U 121 message archiver service. To create the link URL, use the contents of the
122 ``Message-ID`` header of the message without t !! 122 ``Message-Id`` header of the message without the surrounding angle brackets.
123 For example:: 123 For example::
124 124
125 Link: https://lore.kernel.org/30th.anniver !! 125 Link: https://lore.kernel.org/r/30th.anniversary.repost@klaava.Helsinki.FI/
126 126
127 Please check the link to make sure that it is 127 Please check the link to make sure that it is actually working and points
128 to the relevant message. 128 to the relevant message.
129 129
130 However, try to make your explanation understa 130 However, try to make your explanation understandable without external
131 resources. In addition to giving a URL to a ma 131 resources. In addition to giving a URL to a mailing list archive or bug,
132 summarize the relevant points of the discussio 132 summarize the relevant points of the discussion that led to the
133 patch as submitted. 133 patch as submitted.
134 134
135 In case your patch fixes a bug, use the 'Close 135 In case your patch fixes a bug, use the 'Closes:' tag with a URL referencing
136 the report in the mailing list archives or a p 136 the report in the mailing list archives or a public bug tracker. For example::
137 137
138 Closes: https://example.com/issues/123 138 Closes: https://example.com/issues/1234
139 139
140 Some bug trackers have the ability to close is 140 Some bug trackers have the ability to close issues automatically when a
141 commit with such a tag is applied. Some bots m 141 commit with such a tag is applied. Some bots monitoring mailing lists can
142 also track such tags and take certain actions. 142 also track such tags and take certain actions. Private bug trackers and
143 invalid URLs are forbidden. 143 invalid URLs are forbidden.
144 144
145 If your patch fixes a bug in a specific commit 145 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 146 ``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 147 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 148 lines, tags are exempt from the "wrap at 75 columns" rule in order to simplify
149 parsing scripts. For example:: 149 parsing scripts. For example::
150 150
151 Fixes: 54a4f0239f2e ("KVM: MMU: make k 151 Fixes: 54a4f0239f2e ("KVM: MMU: make kvm_mmu_zap_page() return the number of pages it actually freed")
152 152
153 The following ``git config`` settings can be u 153 The following ``git config`` settings can be used to add a pretty format for
154 outputting the above style in the ``git log`` 154 outputting the above style in the ``git log`` or ``git show`` commands::
155 155
156 [core] 156 [core]
157 abbrev = 12 157 abbrev = 12
158 [pretty] 158 [pretty]
159 fixes = Fixes: %h (\"%s\") 159 fixes = Fixes: %h (\"%s\")
160 160
161 An example call:: 161 An example call::
162 162
163 $ git log -1 --pretty=fixes 54a4f0239f 163 $ git log -1 --pretty=fixes 54a4f0239f2e
164 Fixes: 54a4f0239f2e ("KVM: MMU: make k 164 Fixes: 54a4f0239f2e ("KVM: MMU: make kvm_mmu_zap_page() return the number of pages it actually freed")
165 165
166 .. _split_changes: 166 .. _split_changes:
167 167
168 Separate your changes 168 Separate your changes
169 --------------------- 169 ---------------------
170 170
171 Separate each **logical change** into a separa 171 Separate each **logical change** into a separate patch.
172 172
173 For example, if your changes include both bug 173 For example, if your changes include both bug fixes and performance
174 enhancements for a single driver, separate tho 174 enhancements for a single driver, separate those changes into two
175 or more patches. If your changes include an A 175 or more patches. If your changes include an API update, and a new
176 driver which uses that new API, separate those 176 driver which uses that new API, separate those into two patches.
177 177
178 On the other hand, if you make a single change 178 On the other hand, if you make a single change to numerous files,
179 group those changes into a single patch. Thus 179 group those changes into a single patch. Thus a single logical change
180 is contained within a single patch. 180 is contained within a single patch.
181 181
182 The point to remember is that each patch shoul 182 The point to remember is that each patch should make an easily understood
183 change that can be verified by reviewers. Eac 183 change that can be verified by reviewers. Each patch should be justifiable
184 on its own merits. 184 on its own merits.
185 185
186 If one patch depends on another patch in order 186 If one patch depends on another patch in order for a change to be
187 complete, that is OK. Simply note **"this pat 187 complete, that is OK. Simply note **"this patch depends on patch X"**
188 in your patch description. 188 in your patch description.
189 189
190 When dividing your change into a series of pat 190 When dividing your change into a series of patches, take special care to
191 ensure that the kernel builds and runs properl 191 ensure that the kernel builds and runs properly after each patch in the
192 series. Developers using ``git bisect`` to tr 192 series. Developers using ``git bisect`` to track down a problem can end up
193 splitting your patch series at any point; they 193 splitting your patch series at any point; they will not thank you if you
194 introduce bugs in the middle. 194 introduce bugs in the middle.
195 195
196 If you cannot condense your patch set into a s 196 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 197 then only post say 15 or so at a time and wait for review and integration.
198 198
199 199
200 200
201 Style-check your changes 201 Style-check your changes
202 ------------------------ 202 ------------------------
203 203
204 Check your patch for basic style violations, d 204 Check your patch for basic style violations, details of which can be
205 found in Documentation/process/coding-style.rs 205 found in Documentation/process/coding-style.rst.
206 Failure to do so simply wastes 206 Failure to do so simply wastes
207 the reviewers time and will get your patch rej 207 the reviewers time and will get your patch rejected, probably
208 without even being read. 208 without even being read.
209 209
210 One significant exception is when moving code 210 One significant exception is when moving code from one file to
211 another -- in this case you should not modify 211 another -- in this case you should not modify the moved code at all in
212 the same patch which moves it. This clearly d 212 the same patch which moves it. This clearly delineates the act of
213 moving the code and your changes. This greatl 213 moving the code and your changes. This greatly aids review of the
214 actual differences and allows tools to better 214 actual differences and allows tools to better track the history of
215 the code itself. 215 the code itself.
216 216
217 Check your patches with the patch style checke 217 Check your patches with the patch style checker prior to submission
218 (scripts/checkpatch.pl). Note, though, that t 218 (scripts/checkpatch.pl). Note, though, that the style checker should be
219 viewed as a guide, not as a replacement for hu 219 viewed as a guide, not as a replacement for human judgment. If your code
220 looks better with a violation then its probabl 220 looks better with a violation then its probably best left alone.
221 221
222 The checker reports at three levels: 222 The checker reports at three levels:
223 - ERROR: things that are very likely to be wr 223 - ERROR: things that are very likely to be wrong
224 - WARNING: things requiring careful review 224 - WARNING: things requiring careful review
225 - CHECK: things requiring thought 225 - CHECK: things requiring thought
226 226
227 You should be able to justify all violations t 227 You should be able to justify all violations that remain in your
228 patch. 228 patch.
229 229
230 230
231 Select the recipients for your patch 231 Select the recipients for your patch
232 ------------------------------------ 232 ------------------------------------
233 233
234 You should always copy the appropriate subsyst 234 You should always copy the appropriate subsystem maintainer(s) and list(s) on
235 any patch to code that they maintain; look thr 235 any patch to code that they maintain; look through the MAINTAINERS file and the
236 source code revision history to see who those 236 source code revision history to see who those maintainers are. The script
237 scripts/get_maintainer.pl can be very useful a 237 scripts/get_maintainer.pl can be very useful at this step (pass paths to your
238 patches as arguments to scripts/get_maintainer 238 patches as arguments to scripts/get_maintainer.pl). If you cannot find a
239 maintainer for the subsystem you are working o 239 maintainer for the subsystem you are working on, Andrew Morton
240 (akpm@linux-foundation.org) serves as a mainta 240 (akpm@linux-foundation.org) serves as a maintainer of last resort.
241 241
242 linux-kernel@vger.kernel.org should be used by 242 linux-kernel@vger.kernel.org should be used by default for all patches, but the
243 volume on that list has caused a number of dev 243 volume on that list has caused a number of developers to tune it out. Please
244 do not spam unrelated lists and unrelated peop 244 do not spam unrelated lists and unrelated people, though.
245 245
246 Many kernel-related lists are hosted at kernel !! 246 Many kernel-related lists are hosted on vger.kernel.org; you can find a
247 of them at https://subspace.kernel.org. There !! 247 list of them at http://vger.kernel.org/vger-lists.html. There are
248 hosted elsewhere as well, though. !! 248 kernel-related lists hosted elsewhere as well, though.
>> 249
>> 250 Do not send more than 15 patches at once to the vger mailing lists!!!
249 251
250 Linus Torvalds is the final arbiter of all cha 252 Linus Torvalds is the final arbiter of all changes accepted into the
251 Linux kernel. His e-mail address is <torvalds@ 253 Linux kernel. His e-mail address is <torvalds@linux-foundation.org>.
252 He gets a lot of e-mail, and, at this point, v 254 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 255 Linus directly, so typically you should do your best to -avoid-
254 sending him e-mail. 256 sending him e-mail.
255 257
256 If you have a patch that fixes an exploitable 258 If you have a patch that fixes an exploitable security bug, send that patch
257 to security@kernel.org. For severe bugs, a sh 259 to security@kernel.org. For severe bugs, a short embargo may be considered
258 to allow distributors to get the patch out to 260 to allow distributors to get the patch out to users; in such cases,
259 obviously, the patch should not be sent to any 261 obviously, the patch should not be sent to any public lists. See also
260 Documentation/process/security-bugs.rst. 262 Documentation/process/security-bugs.rst.
261 263
262 Patches that fix a severe bug in a released ke 264 Patches that fix a severe bug in a released kernel should be directed
263 toward the stable maintainers by putting a lin 265 toward the stable maintainers by putting a line like this::
264 266
265 Cc: stable@vger.kernel.org 267 Cc: stable@vger.kernel.org
266 268
267 into the sign-off area of your patch (note, NO 269 into the sign-off area of your patch (note, NOT an email recipient). You
268 should also read Documentation/process/stable- 270 should also read Documentation/process/stable-kernel-rules.rst
269 in addition to this document. 271 in addition to this document.
270 272
271 If changes affect userland-kernel interfaces, 273 If changes affect userland-kernel interfaces, please send the MAN-PAGES
272 maintainer (as listed in the MAINTAINERS file) 274 maintainer (as listed in the MAINTAINERS file) a man-pages patch, or at
273 least a notification of the change, so that so 275 least a notification of the change, so that some information makes its way
274 into the manual pages. User-space API changes 276 into the manual pages. User-space API changes should also be copied to
275 linux-api@vger.kernel.org. 277 linux-api@vger.kernel.org.
276 278
277 279
278 No MIME, no links, no compression, no attachme 280 No MIME, no links, no compression, no attachments. Just plain text
279 ---------------------------------------------- 281 -------------------------------------------------------------------
280 282
281 Linus and other kernel developers need to be a 283 Linus and other kernel developers need to be able to read and comment
282 on the changes you are submitting. It is impo 284 on the changes you are submitting. It is important for a kernel
283 developer to be able to "quote" your changes, 285 developer to be able to "quote" your changes, using standard e-mail
284 tools, so that they may comment on specific po 286 tools, so that they may comment on specific portions of your code.
285 287
286 For this reason, all patches should be submitt 288 For this reason, all patches should be submitted by e-mail "inline". The
287 easiest way to do this is with ``git send-emai 289 easiest way to do this is with ``git send-email``, which is strongly
288 recommended. An interactive tutorial for ``gi 290 recommended. An interactive tutorial for ``git send-email`` is available at
289 https://git-send-email.io. 291 https://git-send-email.io.
290 292
291 If you choose not to use ``git send-email``: 293 If you choose not to use ``git send-email``:
292 294
293 .. warning:: 295 .. warning::
294 296
295 Be wary of your editor's word-wrap corruptin 297 Be wary of your editor's word-wrap corrupting your patch,
296 if you choose to cut-n-paste your patch. 298 if you choose to cut-n-paste your patch.
297 299
298 Do not attach the patch as a MIME attachment, 300 Do not attach the patch as a MIME attachment, compressed or not.
299 Many popular e-mail applications will not alwa 301 Many popular e-mail applications will not always transmit a MIME
300 attachment as plain text, making it impossible 302 attachment as plain text, making it impossible to comment on your
301 code. A MIME attachment also takes Linus a bi 303 code. A MIME attachment also takes Linus a bit more time to process,
302 decreasing the likelihood of your MIME-attache 304 decreasing the likelihood of your MIME-attached change being accepted.
303 305
304 Exception: If your mailer is mangling patches 306 Exception: If your mailer is mangling patches then someone may ask
305 you to re-send them using MIME. 307 you to re-send them using MIME.
306 308
307 See Documentation/process/email-clients.rst fo 309 See Documentation/process/email-clients.rst for hints about configuring
308 your e-mail client so that it sends your patch 310 your e-mail client so that it sends your patches untouched.
309 311
310 Respond to review comments 312 Respond to review comments
311 -------------------------- 313 --------------------------
312 314
313 Your patch will almost certainly get comments 315 Your patch will almost certainly get comments from reviewers on ways in
314 which the patch can be improved, in the form o 316 which the patch can be improved, in the form of a reply to your email. You must
315 respond to those comments; ignoring reviewers 317 respond to those comments; ignoring reviewers is a good way to get ignored in
316 return. You can simply reply to their emails t 318 return. You can simply reply to their emails to answer their comments. Review
317 comments or questions that do not lead to a co 319 comments or questions that do not lead to a code change should almost certainly
318 bring about a comment or changelog entry so th 320 bring about a comment or changelog entry so that the next reviewer better
319 understands what is going on. 321 understands what is going on.
320 322
321 Be sure to tell the reviewers what changes you 323 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 324 for their time. Code review is a tiring and time-consuming process, and
323 reviewers sometimes get grumpy. Even in that 325 reviewers sometimes get grumpy. Even in that case, though, respond
324 politely and address the problems they have po 326 politely and address the problems they have pointed out. When sending a next
325 version, add a ``patch changelog`` to the cove 327 version, add a ``patch changelog`` to the cover letter or to individual patches
326 explaining difference against previous submiss 328 explaining difference against previous submission (see
327 :ref:`the_canonical_patch_format`). 329 :ref:`the_canonical_patch_format`).
328 Notify people that commented on your patch abo <<
329 the patches CC list. <<
330 330
331 See Documentation/process/email-clients.rst fo 331 See Documentation/process/email-clients.rst for recommendations on email
332 clients and mailing list etiquette. 332 clients and mailing list etiquette.
333 333
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: 334 .. _resend_reminders:
360 335
361 Don't get discouraged - or impatient 336 Don't get discouraged - or impatient
362 ------------------------------------ 337 ------------------------------------
363 338
364 After you have submitted your change, be patie 339 After you have submitted your change, be patient and wait. Reviewers are
365 busy people and may not get to your patch righ 340 busy people and may not get to your patch right away.
366 341
367 Once upon a time, patches used to disappear in 342 Once upon a time, patches used to disappear into the void without comment,
368 but the development process works more smoothl 343 but the development process works more smoothly than that now. You should
369 receive comments within a few weeks (typically !! 344 receive comments within a week or so; if that does not happen, make sure
370 happen, make sure that you have sent your patc !! 345 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 !! 346 one week before resubmitting or pinging reviewers - possibly longer during
372 - possibly longer during busy times like merge !! 347 busy times like merge windows.
373 348
374 It's also ok to resend the patch or the patch 349 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 350 weeks with the word "RESEND" added to the subject line::
376 351
377 [PATCH Vx RESEND] sub/sys: Condensed patch 352 [PATCH Vx RESEND] sub/sys: Condensed patch summary
378 353
379 Don't add "RESEND" when you are submitting a m 354 Don't add "RESEND" when you are submitting a modified version of your
380 patch or patch series - "RESEND" only applies 355 patch or patch series - "RESEND" only applies to resubmission of a
381 patch or patch series which have not been modi 356 patch or patch series which have not been modified in any way from the
382 previous submission. 357 previous submission.
383 358
384 359
385 Include PATCH in the subject 360 Include PATCH in the subject
386 ----------------------------- 361 -----------------------------
387 362
388 Due to high e-mail traffic to Linus, and to li 363 Due to high e-mail traffic to Linus, and to linux-kernel, it is common
389 convention to prefix your subject line with [P 364 convention to prefix your subject line with [PATCH]. This lets Linus
390 and other kernel developers more easily distin 365 and other kernel developers more easily distinguish patches from other
391 e-mail discussions. 366 e-mail discussions.
392 367
393 ``git send-email`` will do this for you automa 368 ``git send-email`` will do this for you automatically.
394 369
395 370
396 Sign your work - the Developer's Certificate o 371 Sign your work - the Developer's Certificate of Origin
397 ---------------------------------------------- 372 ------------------------------------------------------
398 373
399 To improve tracking of who did what, especiall 374 To improve tracking of who did what, especially with patches that can
400 percolate to their final resting place in the 375 percolate to their final resting place in the kernel through several
401 layers of maintainers, we've introduced a "sig 376 layers of maintainers, we've introduced a "sign-off" procedure on
402 patches that are being emailed around. 377 patches that are being emailed around.
403 378
404 The sign-off is a simple line at the end of th 379 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 380 patch, which certifies that you wrote it or otherwise have the right to
406 pass it on as an open-source patch. The rules 381 pass it on as an open-source patch. The rules are pretty simple: if you
407 can certify the below: 382 can certify the below:
408 383
409 Developer's Certificate of Origin 1.1 384 Developer's Certificate of Origin 1.1
410 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 385 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
411 386
412 By making a contribution to this project, I ce 387 By making a contribution to this project, I certify that:
413 388
414 (a) The contribution was created in wh 389 (a) The contribution was created in whole or in part by me and I
415 have the right to submit it under 390 have the right to submit it under the open source license
416 indicated in the file; or 391 indicated in the file; or
417 392
418 (b) The contribution is based upon pre 393 (b) The contribution is based upon previous work that, to the best
419 of my knowledge, is covered under 394 of my knowledge, is covered under an appropriate open source
420 license and I have the right under 395 license and I have the right under that license to submit that
421 work with modifications, whether c 396 work with modifications, whether created in whole or in part
422 by me, under the same open source 397 by me, under the same open source license (unless I am
423 permitted to submit under a differ 398 permitted to submit under a different license), as indicated
424 in the file; or 399 in the file; or
425 400
426 (c) The contribution was provided dire 401 (c) The contribution was provided directly to me by some other
427 person who certified (a), (b) or ( 402 person who certified (a), (b) or (c) and I have not modified
428 it. 403 it.
429 404
430 (d) I understand and agree that this p 405 (d) I understand and agree that this project and the contribution
431 are public and that a record of th 406 are public and that a record of the contribution (including all
432 personal information I submit with 407 personal information I submit with it, including my sign-off) is
433 maintained indefinitely and may be 408 maintained indefinitely and may be redistributed consistent with
434 this project or the open source li 409 this project or the open source license(s) involved.
435 410
436 then you just add a line saying:: 411 then you just add a line saying::
437 412
438 Signed-off-by: Random J Developer <rand 413 Signed-off-by: Random J Developer <random@developer.example.org>
439 414
440 using a known identity (sorry, no anonymous co 415 using a known identity (sorry, no anonymous contributions.)
441 This will be done for you automatically if you 416 This will be done for you automatically if you use ``git commit -s``.
442 Reverts should also include "Signed-off-by". ` 417 Reverts should also include "Signed-off-by". ``git revert -s`` does that
443 for you. 418 for you.
444 419
445 Some people also put extra tags at the end. T 420 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 421 now, but you can do this to mark internal company procedures or just
447 point out some special detail about the sign-o 422 point out some special detail about the sign-off.
448 423
449 Any further SoBs (Signed-off-by:'s) following 424 Any further SoBs (Signed-off-by:'s) following the author's SoB are from
450 people handling and transporting the patch, bu 425 people handling and transporting the patch, but were not involved in its
451 development. SoB chains should reflect the **r 426 development. SoB chains should reflect the **real** route a patch took
452 as it was propagated to the maintainers and ul 427 as it was propagated to the maintainers and ultimately to Linus, with
453 the first SoB entry signalling primary authors 428 the first SoB entry signalling primary authorship of a single author.
454 429
455 430
456 When to use Acked-by:, Cc:, and Co-developed-b 431 When to use Acked-by:, Cc:, and Co-developed-by:
457 ---------------------------------------------- 432 ------------------------------------------------
458 433
459 The Signed-off-by: tag indicates that the sign 434 The Signed-off-by: tag indicates that the signer was involved in the
460 development of the patch, or that he/she was i 435 development of the patch, or that he/she was in the patch's delivery path.
461 436
462 If a person was not directly involved in the p 437 If a person was not directly involved in the preparation or handling of a
463 patch but wishes to signify and record their a 438 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 439 ask to have an Acked-by: line added to the patch's changelog.
465 440
466 Acked-by: is often used by the maintainer of t 441 Acked-by: is often used by the maintainer of the affected code when that
467 maintainer neither contributed to nor forwarde 442 maintainer neither contributed to nor forwarded the patch.
468 443
469 Acked-by: is not as formal as Signed-off-by:. 444 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 445 has at least reviewed the patch and has indicated acceptance. Hence patch
471 mergers will sometimes manually convert an ack 446 mergers will sometimes manually convert an acker's "yep, looks good to me"
472 into an Acked-by: (but note that it is usually 447 into an Acked-by: (but note that it is usually better to ask for an
473 explicit ack). 448 explicit ack).
474 449
475 Acked-by: does not necessarily indicate acknow 450 Acked-by: does not necessarily indicate acknowledgement of the entire patch.
476 For example, if a patch affects multiple subsy 451 For example, if a patch affects multiple subsystems and has an Acked-by: from
477 one subsystem maintainer then this usually ind 452 one subsystem maintainer then this usually indicates acknowledgement of just
478 the part which affects that maintainer's code. 453 the part which affects that maintainer's code. Judgement should be used here.
479 When in doubt people should refer to the origi 454 When in doubt people should refer to the original discussion in the mailing
480 list archives. 455 list archives.
481 456
482 If a person has had the opportunity to comment 457 If a person has had the opportunity to comment on a patch, but has not
483 provided such comments, you may optionally add 458 provided such comments, you may optionally add a ``Cc:`` tag to the patch.
484 This is the only tag which might be added with 459 This is the only tag which might be added without an explicit action by the
485 person it names - but it should indicate that 460 person it names - but it should indicate that this person was copied on the
486 patch. This tag documents that potentially in 461 patch. This tag documents that potentially interested parties
487 have been included in the discussion. 462 have been included in the discussion.
488 463
489 Co-developed-by: states that the patch was co- 464 Co-developed-by: states that the patch was co-created by multiple developers;
490 it is used to give attribution to co-authors ( 465 it is used to give attribution to co-authors (in addition to the author
491 attributed by the From: tag) when several peop 466 attributed by the From: tag) when several people work on a single patch. Since
492 Co-developed-by: denotes authorship, every Co- 467 Co-developed-by: denotes authorship, every Co-developed-by: must be immediately
493 followed by a Signed-off-by: of the associated 468 followed by a Signed-off-by: of the associated co-author. Standard sign-off
494 procedure applies, i.e. the ordering of Signed 469 procedure applies, i.e. the ordering of Signed-off-by: tags should reflect the
495 chronological history of the patch insofar as 470 chronological history of the patch insofar as possible, regardless of whether
496 the author is attributed via From: or Co-devel 471 the author is attributed via From: or Co-developed-by:. Notably, the last
497 Signed-off-by: must always be that of the deve 472 Signed-off-by: must always be that of the developer submitting the patch.
498 473
499 Note, the From: tag is optional when the From: 474 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 475 email) listed in the From: line of the email header.
501 476
502 Example of a patch submitted by the From: auth 477 Example of a patch submitted by the From: author::
503 478
504 <changelog> 479 <changelog>
505 480
506 Co-developed-by: First Co-Author <first 481 Co-developed-by: First Co-Author <first@coauthor.example.org>
507 Signed-off-by: First Co-Author <first@c 482 Signed-off-by: First Co-Author <first@coauthor.example.org>
508 Co-developed-by: Second Co-Author <seco 483 Co-developed-by: Second Co-Author <second@coauthor.example.org>
509 Signed-off-by: Second Co-Author <second 484 Signed-off-by: Second Co-Author <second@coauthor.example.org>
510 Signed-off-by: From Author <from@author 485 Signed-off-by: From Author <from@author.example.org>
511 486
512 Example of a patch submitted by a Co-developed 487 Example of a patch submitted by a Co-developed-by: author::
513 488
514 From: From Author <from@author.example. 489 From: From Author <from@author.example.org>
515 490
516 <changelog> 491 <changelog>
517 492
518 Co-developed-by: Random Co-Author <rand 493 Co-developed-by: Random Co-Author <random@coauthor.example.org>
519 Signed-off-by: Random Co-Author <random 494 Signed-off-by: Random Co-Author <random@coauthor.example.org>
520 Signed-off-by: From Author <from@author 495 Signed-off-by: From Author <from@author.example.org>
521 Co-developed-by: Submitting Co-Author < 496 Co-developed-by: Submitting Co-Author <sub@coauthor.example.org>
522 Signed-off-by: Submitting Co-Author <su 497 Signed-off-by: Submitting Co-Author <sub@coauthor.example.org>
523 498
524 499
525 Using Reported-by:, Tested-by:, Reviewed-by:, 500 Using Reported-by:, Tested-by:, Reviewed-by:, Suggested-by: and Fixes:
526 ---------------------------------------------- 501 ----------------------------------------------------------------------
527 502
528 The Reported-by tag gives credit to people who 503 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 504 hopefully inspires them to help us again in the future. The tag is intended for
530 bugs; please do not use it to credit feature r 505 bugs; please do not use it to credit feature requests. The tag should be
531 followed by a Closes: tag pointing to the repo 506 followed by a Closes: tag pointing to the report, unless the report is not
532 available on the web. The Link: tag can be use 507 available on the web. The Link: tag can be used instead of Closes: if the patch
533 fixes a part of the issue(s) being reported. P 508 fixes a part of the issue(s) being reported. Please note that if the bug was
534 reported in private, then ask for permission f 509 reported in private, then ask for permission first before using the Reported-by
535 tag. 510 tag.
536 511
537 A Tested-by: tag indicates that the patch has 512 A Tested-by: tag indicates that the patch has been successfully tested (in
538 some environment) by the person named. This t 513 some environment) by the person named. This tag informs maintainers that
539 some testing has been performed, provides a me 514 some testing has been performed, provides a means to locate testers for
540 future patches, and ensures credit for the tes 515 future patches, and ensures credit for the testers.
541 516
542 Reviewed-by:, instead, indicates that the patc 517 Reviewed-by:, instead, indicates that the patch has been reviewed and found
543 acceptable according to the Reviewer's Stateme 518 acceptable according to the Reviewer's Statement:
544 519
545 Reviewer's statement of oversight 520 Reviewer's statement of oversight
546 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 521 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
547 522
548 By offering my Reviewed-by: tag, I state that: 523 By offering my Reviewed-by: tag, I state that:
549 524
550 (a) I have carried out a technical re 525 (a) I have carried out a technical review of this patch to
551 evaluate its appropriateness and 526 evaluate its appropriateness and readiness for inclusion into
552 the mainline kernel. 527 the mainline kernel.
553 528
554 (b) Any problems, concerns, or questi 529 (b) Any problems, concerns, or questions relating to the patch
555 have been communicated back to th 530 have been communicated back to the submitter. I am satisfied
556 with the submitter's response to 531 with the submitter's response to my comments.
557 532
558 (c) While there may be things that co 533 (c) While there may be things that could be improved with this
559 submission, I believe that it is, 534 submission, I believe that it is, at this time, (1) a
560 worthwhile modification to the ke 535 worthwhile modification to the kernel, and (2) free of known
561 issues which would argue against 536 issues which would argue against its inclusion.
562 537
563 (d) While I have reviewed the patch a 538 (d) While I have reviewed the patch and believe it to be sound, I
564 do not (unless explicitly stated 539 do not (unless explicitly stated elsewhere) make any
565 warranties or guarantees that it 540 warranties or guarantees that it will achieve its stated
566 purpose or function properly in a 541 purpose or function properly in any given situation.
567 542
568 A Reviewed-by tag is a statement of opinion th 543 A Reviewed-by tag is a statement of opinion that the patch is an
569 appropriate modification of the kernel without 544 appropriate modification of the kernel without any remaining serious
570 technical issues. Any interested reviewer (wh 545 technical issues. Any interested reviewer (who has done the work) can
571 offer a Reviewed-by tag for a patch. This tag 546 offer a Reviewed-by tag for a patch. This tag serves to give credit to
572 reviewers and to inform maintainers of the deg 547 reviewers and to inform maintainers of the degree of review which has been
573 done on the patch. Reviewed-by: tags, when su 548 done on the patch. Reviewed-by: tags, when supplied by reviewers known to
574 understand the subject area and to perform tho 549 understand the subject area and to perform thorough reviews, will normally
575 increase the likelihood of your patch getting 550 increase the likelihood of your patch getting into the kernel.
576 551
577 Both Tested-by and Reviewed-by tags, once rece 552 Both Tested-by and Reviewed-by tags, once received on mailing list from tester
578 or reviewer, should be added by author to the 553 or reviewer, should be added by author to the applicable patches when sending
579 next versions. However if the patch has chang 554 next versions. However if the patch has changed substantially in following
580 version, these tags might not be applicable an 555 version, these tags might not be applicable anymore and thus should be removed.
581 Usually removal of someone's Tested-by or Revi 556 Usually removal of someone's Tested-by or Reviewed-by tags should be mentioned
582 in the patch changelog (after the '---' separa 557 in the patch changelog (after the '---' separator).
583 558
584 A Suggested-by: tag indicates that the patch i 559 A Suggested-by: tag indicates that the patch idea is suggested by the person
585 named and ensures credit to the person for the 560 named and ensures credit to the person for the idea. Please note that this
586 tag should not be added without the reporter's 561 tag should not be added without the reporter's permission, especially if the
587 idea was not posted in a public forum. That sa 562 idea was not posted in a public forum. That said, if we diligently credit our
588 idea reporters, they will, hopefully, be inspi 563 idea reporters, they will, hopefully, be inspired to help us again in the
589 future. 564 future.
590 565
591 A Fixes: tag indicates that the patch fixes an 566 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 567 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 568 review a bug fix. This tag also assists the stable kernel team in determining
594 which stable kernel versions should receive yo 569 which stable kernel versions should receive your fix. This is the preferred
595 method for indicating a bug fixed by the patch 570 method for indicating a bug fixed by the patch. See :ref:`describe_changes`
596 for more details. 571 for more details.
597 572
598 Note: Attaching a Fixes: tag does not subvert 573 Note: Attaching a Fixes: tag does not subvert the stable kernel rules
599 process nor the requirement to Cc: stable@vger 574 process nor the requirement to Cc: stable@vger.kernel.org on all stable
600 patch candidates. For more information, please 575 patch candidates. For more information, please read
601 Documentation/process/stable-kernel-rules.rst. 576 Documentation/process/stable-kernel-rules.rst.
602 577
603 .. _the_canonical_patch_format: 578 .. _the_canonical_patch_format:
604 579
605 The canonical patch format 580 The canonical patch format
606 -------------------------- 581 --------------------------
607 582
608 This section describes how the patch itself sh 583 This section describes how the patch itself should be formatted. Note
609 that, if you have your patches stored in a ``g 584 that, if you have your patches stored in a ``git`` repository, proper patch
610 formatting can be had with ``git format-patch` 585 formatting can be had with ``git format-patch``. The tools cannot create
611 the necessary text, though, so read the instru 586 the necessary text, though, so read the instructions below anyway.
612 587
613 The canonical patch subject line is:: 588 The canonical patch subject line is::
614 589
615 Subject: [PATCH 001/123] subsystem: summar 590 Subject: [PATCH 001/123] subsystem: summary phrase
616 591
617 The canonical patch message body contains the 592 The canonical patch message body contains the following:
618 593
619 - A ``from`` line specifying the patch autho 594 - A ``from`` line specifying the patch author, followed by an empty
620 line (only needed if the person sending th 595 line (only needed if the person sending the patch is not the author).
621 596
622 - The body of the explanation, line wrapped 597 - The body of the explanation, line wrapped at 75 columns, which will
623 be copied to the permanent changelog to de 598 be copied to the permanent changelog to describe this patch.
624 599
625 - An empty line. 600 - An empty line.
626 601
627 - The ``Signed-off-by:`` lines, described ab 602 - The ``Signed-off-by:`` lines, described above, which will
628 also go in the changelog. 603 also go in the changelog.
629 604
630 - A marker line containing simply ``---``. 605 - A marker line containing simply ``---``.
631 606
632 - Any additional comments not suitable for t 607 - Any additional comments not suitable for the changelog.
633 608
634 - The actual patch (``diff`` output). 609 - The actual patch (``diff`` output).
635 610
636 The Subject line format makes it very easy to 611 The Subject line format makes it very easy to sort the emails
637 alphabetically by subject line - pretty much a 612 alphabetically by subject line - pretty much any email reader will
638 support that - since because the sequence numb 613 support that - since because the sequence number is zero-padded,
639 the numerical and alphabetic sort is the same. 614 the numerical and alphabetic sort is the same.
640 615
641 The ``subsystem`` in the email's Subject shoul 616 The ``subsystem`` in the email's Subject should identify which
642 area or subsystem of the kernel is being patch 617 area or subsystem of the kernel is being patched.
643 618
644 The ``summary phrase`` in the email's Subject 619 The ``summary phrase`` in the email's Subject should concisely
645 describe the patch which that email contains. 620 describe the patch which that email contains. The ``summary
646 phrase`` should not be a filename. Do not use 621 phrase`` should not be a filename. Do not use the same ``summary
647 phrase`` for every patch in a whole patch seri 622 phrase`` for every patch in a whole patch series (where a ``patch
648 series`` is an ordered sequence of multiple, r 623 series`` is an ordered sequence of multiple, related patches).
649 624
650 Bear in mind that the ``summary phrase`` of yo 625 Bear in mind that the ``summary phrase`` of your email becomes a
651 globally-unique identifier for that patch. It 626 globally-unique identifier for that patch. It propagates all the way
652 into the ``git`` changelog. The ``summary phr 627 into the ``git`` changelog. The ``summary phrase`` may later be used in
653 developer discussions which refer to the patch 628 developer discussions which refer to the patch. People will want to
654 google for the ``summary phrase`` to read disc 629 google for the ``summary phrase`` to read discussion regarding that
655 patch. It will also be the only thing that pe 630 patch. It will also be the only thing that people may quickly see
656 when, two or three months later, they are goin 631 when, two or three months later, they are going through perhaps
657 thousands of patches using tools such as ``git 632 thousands of patches using tools such as ``gitk`` or ``git log
658 --oneline``. 633 --oneline``.
659 634
660 For these reasons, the ``summary`` must be no 635 For these reasons, the ``summary`` must be no more than 70-75
661 characters, and it must describe both what the 636 characters, and it must describe both what the patch changes, as well
662 as why the patch might be necessary. It is ch 637 as why the patch might be necessary. It is challenging to be both
663 succinct and descriptive, but that is what a w 638 succinct and descriptive, but that is what a well-written summary
664 should do. 639 should do.
665 640
666 The ``summary phrase`` may be prefixed by tags 641 The ``summary phrase`` may be prefixed by tags enclosed in square
667 brackets: "Subject: [PATCH <tag>...] <summary 642 brackets: "Subject: [PATCH <tag>...] <summary phrase>". The tags are
668 not considered part of the summary phrase, but 643 not considered part of the summary phrase, but describe how the patch
669 should be treated. Common tags might include 644 should be treated. Common tags might include a version descriptor if
670 the multiple versions of the patch have been s 645 the multiple versions of the patch have been sent out in response to
671 comments (i.e., "v1, v2, v3"), or "RFC" to ind 646 comments (i.e., "v1, v2, v3"), or "RFC" to indicate a request for
672 comments. 647 comments.
673 648
674 If there are four patches in a patch series th 649 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 650 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 651 understand the order in which the patches should be applied and that
677 they have reviewed or applied all of the patch 652 they have reviewed or applied all of the patches in the patch series.
678 653
679 Here are some good example Subjects:: 654 Here are some good example Subjects::
680 655
681 Subject: [PATCH 2/5] ext2: improve scalabi 656 Subject: [PATCH 2/5] ext2: improve scalability of bitmap searching
682 Subject: [PATCH v2 01/27] x86: fix eflags 657 Subject: [PATCH v2 01/27] x86: fix eflags tracking
683 Subject: [PATCH v2] sub/sys: Condensed pat 658 Subject: [PATCH v2] sub/sys: Condensed patch summary
684 Subject: [PATCH v2 M/N] sub/sys: Condensed 659 Subject: [PATCH v2 M/N] sub/sys: Condensed patch summary
685 660
686 The ``from`` line must be the very first line 661 The ``from`` line must be the very first line in the message body,
687 and has the form: 662 and has the form:
688 663
689 From: Patch Author <author@example.com> 664 From: Patch Author <author@example.com>
690 665
691 The ``from`` line specifies who will be credit 666 The ``from`` line specifies who will be credited as the author of the
692 patch in the permanent changelog. If the ``fr 667 patch in the permanent changelog. If the ``from`` line is missing,
693 then the ``From:`` line from the email header 668 then the ``From:`` line from the email header will be used to determine
694 the patch author in the changelog. 669 the patch author in the changelog.
695 670
696 The explanation body will be committed to the 671 The explanation body will be committed to the permanent source
697 changelog, so should make sense to a competent 672 changelog, so should make sense to a competent reader who has long since
698 forgotten the immediate details of the discuss 673 forgotten the immediate details of the discussion that might have led to
699 this patch. Including symptoms of the failure 674 this patch. Including symptoms of the failure which the patch addresses
700 (kernel log messages, oops messages, etc.) are 675 (kernel log messages, oops messages, etc.) are especially useful for
701 people who might be searching the commit logs 676 people who might be searching the commit logs looking for the applicable
702 patch. The text should be written in such deta 677 patch. The text should be written in such detail so that when read
703 weeks, months or even years later, it can give 678 weeks, months or even years later, it can give the reader the needed
704 details to grasp the reasoning for **why** the 679 details to grasp the reasoning for **why** the patch was created.
705 680
706 If a patch fixes a compile failure, it may not 681 If a patch fixes a compile failure, it may not be necessary to include
707 _all_ of the compile failures; just enough tha 682 _all_ of the compile failures; just enough that it is likely that
708 someone searching for the patch can find it. A 683 someone searching for the patch can find it. As in the ``summary
709 phrase``, it is important to be both succinct 684 phrase``, it is important to be both succinct as well as descriptive.
710 685
711 The ``---`` marker line serves the essential p 686 The ``---`` marker line serves the essential purpose of marking for
712 patch handling tools where the changelog messa 687 patch handling tools where the changelog message ends.
713 688
714 One good use for the additional comments after 689 One good use for the additional comments after the ``---`` marker is
715 for a ``diffstat``, to show what files have ch 690 for a ``diffstat``, to show what files have changed, and the number of
716 inserted and deleted lines per file. A ``diffs 691 inserted and deleted lines per file. A ``diffstat`` is especially useful
717 on bigger patches. If you are going to include 692 on bigger patches. If you are going to include a ``diffstat`` after the
718 ``---`` marker, please use ``diffstat`` option 693 ``---`` marker, please use ``diffstat`` options ``-p 1 -w 70`` so that
719 filenames are listed from the top of the kerne 694 filenames are listed from the top of the kernel source tree and don't
720 use too much horizontal space (easily fit in 8 695 use too much horizontal space (easily fit in 80 columns, maybe with some
721 indentation). (``git`` generates appropriate d 696 indentation). (``git`` generates appropriate diffstats by default.)
722 697
723 Other comments relevant only to the moment or 698 Other comments relevant only to the moment or the maintainer, not
724 suitable for the permanent changelog, should a 699 suitable for the permanent changelog, should also go here. A good
725 example of such comments might be ``patch chan 700 example of such comments might be ``patch changelogs`` which describe
726 what has changed between the v1 and v2 version 701 what has changed between the v1 and v2 version of the patch.
727 702
728 Please put this information **after** the ``-- 703 Please put this information **after** the ``---`` line which separates
729 the changelog from the rest of the patch. The 704 the changelog from the rest of the patch. The version information is
730 not part of the changelog which gets committed 705 not part of the changelog which gets committed to the git tree. It is
731 additional information for the reviewers. If i 706 additional information for the reviewers. If it's placed above the
732 commit tags, it needs manual interaction to re 707 commit tags, it needs manual interaction to remove it. If it is below
733 the separator line, it gets automatically stri 708 the separator line, it gets automatically stripped off when applying the
734 patch:: 709 patch::
735 710
736 <commit message> 711 <commit message>
737 ... 712 ...
738 Signed-off-by: Author <author@mail> 713 Signed-off-by: Author <author@mail>
739 --- 714 ---
740 V2 -> V3: Removed redundant helper function 715 V2 -> V3: Removed redundant helper function
741 V1 -> V2: Cleaned up coding style and addres 716 V1 -> V2: Cleaned up coding style and addressed review comments
742 717
743 path/to/file | 5+++-- 718 path/to/file | 5+++--
744 ... 719 ...
745 720
746 See more details on the proper patch format in 721 See more details on the proper patch format in the following
747 references. 722 references.
748 723
749 .. _backtraces: 724 .. _backtraces:
750 725
751 Backtraces in commit messages 726 Backtraces in commit messages
752 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 727 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
753 728
754 Backtraces help document the call chain leadin 729 Backtraces help document the call chain leading to a problem. However,
755 not all backtraces are helpful. For example, e 730 not all backtraces are helpful. For example, early boot call chains are
756 unique and obvious. Copying the full dmesg out 731 unique and obvious. Copying the full dmesg output verbatim, however,
757 adds distracting information like timestamps, 732 adds distracting information like timestamps, module lists, register and
758 stack dumps. 733 stack dumps.
759 734
760 Therefore, the most useful backtraces should d 735 Therefore, the most useful backtraces should distill the relevant
761 information from the dump, which makes it easi 736 information from the dump, which makes it easier to focus on the real
762 issue. Here is an example of a well-trimmed ba 737 issue. Here is an example of a well-trimmed backtrace::
763 738
764 unchecked MSR access error: WRMSR to 0xd51 ( 739 unchecked MSR access error: WRMSR to 0xd51 (tried to write 0x0000000000000064)
765 at rIP: 0xffffffffae059994 (native_write_msr 740 at rIP: 0xffffffffae059994 (native_write_msr+0x4/0x20)
766 Call Trace: 741 Call Trace:
767 mba_wrmsr 742 mba_wrmsr
768 update_domains 743 update_domains
769 rdtgroup_mkdir 744 rdtgroup_mkdir
770 745
771 .. _explicit_in_reply_to: 746 .. _explicit_in_reply_to:
772 747
773 Explicit In-Reply-To headers 748 Explicit In-Reply-To headers
774 ---------------------------- 749 ----------------------------
775 750
776 It can be helpful to manually add In-Reply-To: 751 It can be helpful to manually add In-Reply-To: headers to a patch
777 (e.g., when using ``git send-email``) to assoc 752 (e.g., when using ``git send-email``) to associate the patch with
778 previous relevant discussion, e.g. to link a b 753 previous relevant discussion, e.g. to link a bug fix to the email with
779 the bug report. However, for a multi-patch se 754 the bug report. However, for a multi-patch series, it is generally
780 best to avoid using In-Reply-To: to link to ol 755 best to avoid using In-Reply-To: to link to older versions of the
781 series. This way multiple versions of the pat 756 series. This way multiple versions of the patch don't become an
782 unmanageable forest of references in email cli 757 unmanageable forest of references in email clients. If a link is
783 helpful, you can use the https://lore.kernel.o 758 helpful, you can use the https://lore.kernel.org/ redirector (e.g., in
784 the cover email text) to link to an earlier ve 759 the cover email text) to link to an earlier version of the patch series.
785 760
786 761
787 Providing base tree information 762 Providing base tree information
788 ------------------------------- 763 -------------------------------
789 764
790 When other developers receive your patches and 765 When other developers receive your patches and start the review process,
791 it is absolutely necessary for them to know wh !! 766 it is often useful for them to know where in the tree history they
792 commit/branch your work applies on, considerin !! 767 should place your work. This is particularly useful for automated CI
793 maintainer trees present nowadays. Note again !! 768 processes that attempt to run a series of tests in order to establish
794 MAINTAINERS file explained above. !! 769 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 <<
799 770
800 If you are using ``git format-patch`` to gener 771 If you are using ``git format-patch`` to generate your patches, you can
801 automatically include the base tree informatio 772 automatically include the base tree information in your submission by
802 using the ``--base`` flag. The easiest and mos 773 using the ``--base`` flag. The easiest and most convenient way to use
803 this option is with topical branches:: 774 this option is with topical branches::
804 775
805 $ git checkout -t -b my-topical-branch mas 776 $ git checkout -t -b my-topical-branch master
806 Branch 'my-topical-branch' set up to track 777 Branch 'my-topical-branch' set up to track local branch 'master'.
807 Switched to a new branch 'my-topical-branc 778 Switched to a new branch 'my-topical-branch'
808 779
809 [perform your edits and commits] 780 [perform your edits and commits]
810 781
811 $ git format-patch --base=auto --cover-let 782 $ git format-patch --base=auto --cover-letter -o outgoing/ master
812 outgoing/0000-cover-letter.patch 783 outgoing/0000-cover-letter.patch
813 outgoing/0001-First-Commit.patch 784 outgoing/0001-First-Commit.patch
814 outgoing/... 785 outgoing/...
815 786
816 When you open ``outgoing/0000-cover-letter.pat 787 When you open ``outgoing/0000-cover-letter.patch`` for editing, you will
817 notice that it will have the ``base-commit:`` 788 notice that it will have the ``base-commit:`` trailer at the very
818 bottom, which provides the reviewer and the CI 789 bottom, which provides the reviewer and the CI tools enough information
819 to properly perform ``git am`` without worryin 790 to properly perform ``git am`` without worrying about conflicts::
820 791
821 $ git checkout -b patch-review [base-commi 792 $ git checkout -b patch-review [base-commit-id]
822 Switched to a new branch 'patch-review' 793 Switched to a new branch 'patch-review'
823 $ git am patches.mbox 794 $ git am patches.mbox
824 Applying: First Commit 795 Applying: First Commit
825 Applying: ... 796 Applying: ...
826 797
827 Please see ``man git-format-patch`` for more i 798 Please see ``man git-format-patch`` for more information about this
828 option. 799 option.
829 800
830 .. note:: 801 .. note::
831 802
832 The ``--base`` feature was introduced in g 803 The ``--base`` feature was introduced in git version 2.9.0.
833 804
834 If you are not using git to format your patche 805 If you are not using git to format your patches, you can still include
835 the same ``base-commit`` trailer to indicate t 806 the same ``base-commit`` trailer to indicate the commit hash of the tree
836 on which your work is based. You should add it 807 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 808 letter or in the first patch of the series and it should be placed
838 either below the ``---`` line or at the very b 809 either below the ``---`` line or at the very bottom of all other
839 content, right before your email signature. 810 content, right before your email signature.
840 811
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. <<
852 812
853 References 813 References
854 ---------- 814 ----------
855 815
856 Andrew Morton, "The perfect patch" (tpp). 816 Andrew Morton, "The perfect patch" (tpp).
857 <https://www.ozlabs.org/~akpm/stuff/tpp.txt> 817 <https://www.ozlabs.org/~akpm/stuff/tpp.txt>
858 818
859 Jeff Garzik, "Linux kernel patch submission fo 819 Jeff Garzik, "Linux kernel patch submission format".
860 <https://web.archive.org/web/20180829112450/ 820 <https://web.archive.org/web/20180829112450/http://linux.yyz.us/patch-format.html>
861 821
862 Greg Kroah-Hartman, "How to piss off a kernel 822 Greg Kroah-Hartman, "How to piss off a kernel subsystem maintainer".
863 <http://www.kroah.com/log/linux/maintainer.h 823 <http://www.kroah.com/log/linux/maintainer.html>
864 824
865 <http://www.kroah.com/log/linux/maintainer-0 825 <http://www.kroah.com/log/linux/maintainer-02.html>
866 826
867 <http://www.kroah.com/log/linux/maintainer-0 827 <http://www.kroah.com/log/linux/maintainer-03.html>
868 828
869 <http://www.kroah.com/log/linux/maintainer-0 829 <http://www.kroah.com/log/linux/maintainer-04.html>
870 830
871 <http://www.kroah.com/log/linux/maintainer-0 831 <http://www.kroah.com/log/linux/maintainer-05.html>
872 832
873 <http://www.kroah.com/log/linux/maintainer-0 833 <http://www.kroah.com/log/linux/maintainer-06.html>
>> 834
>> 835 NO!!!! No more huge patch bombs to linux-kernel@vger.kernel.org people!
>> 836 <https://lore.kernel.org/r/20050711.125305.08322243.davem@davemloft.net">https://lore.kernel.org/r/20050711.125305.08322243.davem@davemloft.net>
874 837
875 Kernel Documentation/process/coding-style.rst 838 Kernel Documentation/process/coding-style.rst
876 839
877 Linus Torvalds's mail on the canonical patch f 840 Linus Torvalds's mail on the canonical patch format:
878 <https://lore.kernel.org/r/Pine.LNX.4.58.0504 841 <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>
879 842
880 Andi Kleen, "On submitting kernel patches" 843 Andi Kleen, "On submitting kernel patches"
881 Some strategies to get difficult or controve 844 Some strategies to get difficult or controversial changes in.
882 845
883 http://halobates.de/on-submitting-patches.pd 846 http://halobates.de/on-submitting-patches.pdf
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