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