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