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 :ref:`Documentation/process <development_process_main>`.
14 Documentation/process/submit-checklist.rst !! 14 Also, read :ref:`Documentation/process/submit-checklist.rst <submitchecklist>`
15 for a list of items to check before submitting !! 15 for a list of items to check before
16 For device tree binding patches, read !! 16 submitting code. If you are submitting a driver, also read
17 Documentation/devicetree/bindings/submitting-p !! 17 :ref:`Documentation/process/submitting-drivers.rst <submittingdrivers>`;
18 !! 18 for device tree binding patches, read
19 This documentation assumes that you're using ` !! 19 Documentation/devicetree/bindings/submitting-patches.txt.
20 If you're unfamiliar with ``git``, you would b !! 20
21 use it, it will make your life as a kernel dev !! 21 Many of these steps describe the default behavior of the ``git`` version
22 easier. !! 22 control system; if you use ``git`` to prepare your patches, you'll find much
23 !! 23 of the mechanical work done for you, though you'll still need to prepare
24 Some subsystems and maintainer trees have addi !! 24 and document a sensible set of patches. In general, use of ``git`` will make
25 their workflow and expectations, see !! 25 your life as a kernel developer easier.
26 :ref:`Documentation/process/maintainer-handboo <<
27 26
28 Obtain a current source tree !! 27 0) Obtain a current source tree
29 ---------------------------- !! 28 -------------------------------
30 29
31 If you do not have a repository with the curre 30 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 31 ``git`` to obtain one. You'll want to start with the mainline repository,
33 which can be grabbed with:: 32 which can be grabbed with::
34 33
35 git clone git://git.kernel.org/pub/scm/linux 34 git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
36 35
37 Note, however, that you may not want to develo 36 Note, however, that you may not want to develop against the mainline tree
38 directly. Most subsystem maintainers run thei 37 directly. Most subsystem maintainers run their own trees and want to see
39 patches prepared against those trees. See the 38 patches prepared against those trees. See the **T:** entry for the subsystem
40 in the MAINTAINERS file to find that tree, or 39 in the MAINTAINERS file to find that tree, or simply ask the maintainer if
41 the tree is not listed there. 40 the tree is not listed there.
42 41
>> 42 It is still possible to download kernel releases via tarballs (as described
>> 43 in the next section), but that is the hard way to do kernel development.
>> 44
>> 45 1) ``diff -up``
>> 46 ---------------
>> 47
>> 48 If you must generate your patches by hand, use ``diff -up`` or ``diff -uprN``
>> 49 to create patches. Git generates patches in this form by default; if
>> 50 you're using ``git``, you can skip this section entirely.
>> 51
>> 52 All changes to the Linux kernel occur in the form of patches, as
>> 53 generated by :manpage:`diff(1)`. When creating your patch, make sure to
>> 54 create it in "unified diff" format, as supplied by the ``-u`` argument
>> 55 to :manpage:`diff(1)`.
>> 56 Also, please use the ``-p`` argument which shows which C function each
>> 57 change is in - that makes the resultant ``diff`` a lot easier to read.
>> 58 Patches should be based in the root kernel source directory,
>> 59 not in any lower subdirectory.
>> 60
>> 61 To create a patch for a single file, it is often sufficient to do::
>> 62
>> 63 SRCTREE= linux
>> 64 MYFILE= drivers/net/mydriver.c
>> 65
>> 66 cd $SRCTREE
>> 67 cp $MYFILE $MYFILE.orig
>> 68 vi $MYFILE # make your change
>> 69 cd ..
>> 70 diff -up $SRCTREE/$MYFILE{.orig,} > /tmp/patch
>> 71
>> 72 To create a patch for multiple files, you should unpack a "vanilla",
>> 73 or unmodified kernel source tree, and generate a ``diff`` against your
>> 74 own source tree. For example::
>> 75
>> 76 MYSRC= /devel/linux
>> 77
>> 78 tar xvfz linux-3.19.tar.gz
>> 79 mv linux-3.19 linux-3.19-vanilla
>> 80 diff -uprN -X linux-3.19-vanilla/Documentation/dontdiff \
>> 81 linux-3.19-vanilla $MYSRC > /tmp/patch
>> 82
>> 83 ``dontdiff`` is a list of files which are generated by the kernel during
>> 84 the build process, and should be ignored in any :manpage:`diff(1)`-generated
>> 85 patch.
>> 86
>> 87 Make sure your patch does not include any extra files which do not
>> 88 belong in a patch submission. Make sure to review your patch -after-
>> 89 generating it with :manpage:`diff(1)`, to ensure accuracy.
>> 90
>> 91 If your changes produce a lot of deltas, you need to split them into
>> 92 individual patches which modify things in logical stages; see
>> 93 :ref:`split_changes`. This will facilitate review by other kernel developers,
>> 94 very important if you want your patch accepted.
>> 95
>> 96 If you're using ``git``, ``git rebase -i`` can help you with this process. If
>> 97 you're not using ``git``, ``quilt`` <http://savannah.nongnu.org/projects/quilt>
>> 98 is another popular alternative.
>> 99
43 .. _describe_changes: 100 .. _describe_changes:
44 101
45 Describe your changes !! 102 2) Describe your changes
46 --------------------- !! 103 ------------------------
47 104
48 Describe your problem. Whether your patch is 105 Describe your problem. Whether your patch is a one-line bug fix or
49 5000 lines of a new feature, there must be an 106 5000 lines of a new feature, there must be an underlying problem that
50 motivated you to do this work. Convince the r 107 motivated you to do this work. Convince the reviewer that there is a
51 problem worth fixing and that it makes sense f 108 problem worth fixing and that it makes sense for them to read past the
52 first paragraph. 109 first paragraph.
53 110
54 Describe user-visible impact. Straight up cra 111 Describe user-visible impact. Straight up crashes and lockups are
55 pretty convincing, but not all bugs are that b 112 pretty convincing, but not all bugs are that blatant. Even if the
56 problem was spotted during code review, descri 113 problem was spotted during code review, describe the impact you think
57 it can have on users. Keep in mind that the m 114 it can have on users. Keep in mind that the majority of Linux
58 installations run kernels from secondary stabl 115 installations run kernels from secondary stable trees or
59 vendor/product-specific trees that cherry-pick 116 vendor/product-specific trees that cherry-pick only specific patches
60 from upstream, so include anything that could 117 from upstream, so include anything that could help route your change
61 downstream: provoking circumstances, excerpts 118 downstream: provoking circumstances, excerpts from dmesg, crash
62 descriptions, performance regressions, latency 119 descriptions, performance regressions, latency spikes, lockups, etc.
63 120
64 Quantify optimizations and trade-offs. If you 121 Quantify optimizations and trade-offs. If you claim improvements in
65 performance, memory consumption, stack footpri 122 performance, memory consumption, stack footprint, or binary size,
66 include numbers that back them up. But also d 123 include numbers that back them up. But also describe non-obvious
67 costs. Optimizations usually aren't free but 124 costs. Optimizations usually aren't free but trade-offs between CPU,
68 memory, and readability; or, when it comes to 125 memory, and readability; or, when it comes to heuristics, between
69 different workloads. Describe the expected do 126 different workloads. Describe the expected downsides of your
70 optimization so that the reviewer can weigh co 127 optimization so that the reviewer can weigh costs against benefits.
71 128
72 Once the problem is established, describe what 129 Once the problem is established, describe what you are actually doing
73 about it in technical detail. It's important 130 about it in technical detail. It's important to describe the change
74 in plain English for the reviewer to verify th 131 in plain English for the reviewer to verify that the code is behaving
75 as you intend it to. 132 as you intend it to.
76 133
77 The maintainer will thank you if you write you 134 The maintainer will thank you if you write your patch description in a
78 form which can be easily pulled into Linux's s 135 form which can be easily pulled into Linux's source code management
79 system, ``git``, as a "commit log". See :ref: !! 136 system, ``git``, as a "commit log". See :ref:`explicit_in_reply_to`.
80 137
81 Solve only one problem per patch. If your des 138 Solve only one problem per patch. If your description starts to get
82 long, that's a sign that you probably need to 139 long, that's a sign that you probably need to split up your patch.
83 See :ref:`split_changes`. 140 See :ref:`split_changes`.
84 141
85 When you submit or resubmit a patch or patch s 142 When you submit or resubmit a patch or patch series, include the
86 complete patch description and justification f 143 complete patch description and justification for it. Don't just
87 say that this is version N of the patch (serie 144 say that this is version N of the patch (series). Don't expect the
88 subsystem maintainer to refer back to earlier 145 subsystem maintainer to refer back to earlier patch versions or referenced
89 URLs to find the patch description and put tha 146 URLs to find the patch description and put that into the patch.
90 I.e., the patch (series) and its description s 147 I.e., the patch (series) and its description should be self-contained.
91 This benefits both the maintainers and reviewe 148 This benefits both the maintainers and reviewers. Some reviewers
92 probably didn't even receive earlier versions 149 probably didn't even receive earlier versions of the patch.
93 150
94 Describe your changes in imperative mood, e.g. 151 Describe your changes in imperative mood, e.g. "make xyzzy do frotz"
95 instead of "[This patch] makes xyzzy do frotz" 152 instead of "[This patch] makes xyzzy do frotz" or "[I] changed xyzzy
96 to do frotz", as if you are giving orders to t 153 to do frotz", as if you are giving orders to the codebase to change
97 its behaviour. 154 its behaviour.
98 155
>> 156 If the patch fixes a logged bug entry, refer to that bug entry by
>> 157 number and URL. If the patch follows from a mailing list discussion,
>> 158 give a URL to the mailing list archive; use the https://lkml.kernel.org/
>> 159 redirector with a ``Message-Id``, to ensure that the links cannot become
>> 160 stale.
>> 161
>> 162 However, try to make your explanation understandable without external
>> 163 resources. In addition to giving a URL to a mailing list archive or
>> 164 bug, summarize the relevant points of the discussion that led to the
>> 165 patch as submitted.
>> 166
99 If you want to refer to a specific commit, don 167 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 168 SHA-1 ID of the commit. Please also include the oneline summary of
101 the commit, to make it easier for reviewers to 169 the commit, to make it easier for reviewers to know what it is about.
102 Example:: 170 Example::
103 171
104 Commit e21d2170f36602ae2708 ("video: r 172 Commit e21d2170f36602ae2708 ("video: remove unnecessary
105 platform_set_drvdata()") removed the u 173 platform_set_drvdata()") removed the unnecessary
106 platform_set_drvdata(), but left the v 174 platform_set_drvdata(), but left the variable "dev" unused,
107 delete it. 175 delete it.
108 176
109 You should also be sure to use at least the fi 177 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* 178 SHA-1 ID. The kernel repository holds a *lot* of objects, making
111 collisions with shorter IDs a real possibility 179 collisions with shorter IDs a real possibility. Bear in mind that, even if
112 there is no collision with your six-character 180 there is no collision with your six-character ID now, that condition may
113 change five years from now. 181 change five years from now.
114 182
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 183 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 184 ``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 185 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 186 lines, tags are exempt from the "wrap at 75 columns" rule in order to simplify
149 parsing scripts. For example:: 187 parsing scripts. For example::
150 188
151 Fixes: 54a4f0239f2e ("KVM: MMU: make k 189 Fixes: 54a4f0239f2e ("KVM: MMU: make kvm_mmu_zap_page() return the number of pages it actually freed")
152 190
153 The following ``git config`` settings can be u 191 The following ``git config`` settings can be used to add a pretty format for
154 outputting the above style in the ``git log`` 192 outputting the above style in the ``git log`` or ``git show`` commands::
155 193
156 [core] 194 [core]
157 abbrev = 12 195 abbrev = 12
158 [pretty] 196 [pretty]
159 fixes = Fixes: %h (\"%s\") 197 fixes = Fixes: %h (\"%s\")
160 198
161 An example call:: <<
162 <<
163 $ git log -1 --pretty=fixes 54a4f0239f <<
164 Fixes: 54a4f0239f2e ("KVM: MMU: make k <<
165 <<
166 .. _split_changes: 199 .. _split_changes:
167 200
168 Separate your changes !! 201 3) Separate your changes
169 --------------------- !! 202 ------------------------
170 203
171 Separate each **logical change** into a separa 204 Separate each **logical change** into a separate patch.
172 205
173 For example, if your changes include both bug 206 For example, if your changes include both bug fixes and performance
174 enhancements for a single driver, separate tho 207 enhancements for a single driver, separate those changes into two
175 or more patches. If your changes include an A 208 or more patches. If your changes include an API update, and a new
176 driver which uses that new API, separate those 209 driver which uses that new API, separate those into two patches.
177 210
178 On the other hand, if you make a single change 211 On the other hand, if you make a single change to numerous files,
179 group those changes into a single patch. Thus 212 group those changes into a single patch. Thus a single logical change
180 is contained within a single patch. 213 is contained within a single patch.
181 214
182 The point to remember is that each patch shoul 215 The point to remember is that each patch should make an easily understood
183 change that can be verified by reviewers. Eac 216 change that can be verified by reviewers. Each patch should be justifiable
184 on its own merits. 217 on its own merits.
185 218
186 If one patch depends on another patch in order 219 If one patch depends on another patch in order for a change to be
187 complete, that is OK. Simply note **"this pat 220 complete, that is OK. Simply note **"this patch depends on patch X"**
188 in your patch description. 221 in your patch description.
189 222
190 When dividing your change into a series of pat 223 When dividing your change into a series of patches, take special care to
191 ensure that the kernel builds and runs properl 224 ensure that the kernel builds and runs properly after each patch in the
192 series. Developers using ``git bisect`` to tr 225 series. Developers using ``git bisect`` to track down a problem can end up
193 splitting your patch series at any point; they 226 splitting your patch series at any point; they will not thank you if you
194 introduce bugs in the middle. 227 introduce bugs in the middle.
195 228
196 If you cannot condense your patch set into a s 229 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 230 then only post say 15 or so at a time and wait for review and integration.
198 231
199 232
200 233
201 Style-check your changes !! 234 4) Style-check your changes
202 ------------------------ !! 235 ---------------------------
203 236
204 Check your patch for basic style violations, d 237 Check your patch for basic style violations, details of which can be
205 found in Documentation/process/coding-style.rs !! 238 found in
>> 239 :ref:`Documentation/process/coding-style.rst <codingstyle>`.
206 Failure to do so simply wastes 240 Failure to do so simply wastes
207 the reviewers time and will get your patch rej 241 the reviewers time and will get your patch rejected, probably
208 without even being read. 242 without even being read.
209 243
210 One significant exception is when moving code 244 One significant exception is when moving code from one file to
211 another -- in this case you should not modify 245 another -- in this case you should not modify the moved code at all in
212 the same patch which moves it. This clearly d 246 the same patch which moves it. This clearly delineates the act of
213 moving the code and your changes. This greatl 247 moving the code and your changes. This greatly aids review of the
214 actual differences and allows tools to better 248 actual differences and allows tools to better track the history of
215 the code itself. 249 the code itself.
216 250
217 Check your patches with the patch style checke 251 Check your patches with the patch style checker prior to submission
218 (scripts/checkpatch.pl). Note, though, that t 252 (scripts/checkpatch.pl). Note, though, that the style checker should be
219 viewed as a guide, not as a replacement for hu 253 viewed as a guide, not as a replacement for human judgment. If your code
220 looks better with a violation then its probabl 254 looks better with a violation then its probably best left alone.
221 255
222 The checker reports at three levels: 256 The checker reports at three levels:
223 - ERROR: things that are very likely to be wr 257 - ERROR: things that are very likely to be wrong
224 - WARNING: things requiring careful review 258 - WARNING: things requiring careful review
225 - CHECK: things requiring thought 259 - CHECK: things requiring thought
226 260
227 You should be able to justify all violations t 261 You should be able to justify all violations that remain in your
228 patch. 262 patch.
229 263
230 264
231 Select the recipients for your patch !! 265 5) Select the recipients for your patch
232 ------------------------------------ !! 266 ---------------------------------------
>> 267
>> 268 You should always copy the appropriate subsystem maintainer(s) on any patch
>> 269 to code that they maintain; look through the MAINTAINERS file and the
>> 270 source code revision history to see who those maintainers are. The
>> 271 script scripts/get_maintainer.pl can be very useful at this step. If you
>> 272 cannot find a maintainer for the subsystem you are working on, Andrew
>> 273 Morton (akpm@linux-foundation.org) serves as a maintainer of last resort.
>> 274
>> 275 You should also normally choose at least one mailing list to receive a copy
>> 276 of your patch set. linux-kernel@vger.kernel.org functions as a list of
>> 277 last resort, but the volume on that list has caused a number of developers
>> 278 to tune it out. Look in the MAINTAINERS file for a subsystem-specific
>> 279 list; your patch will probably get more attention there. Please do not
>> 280 spam unrelated lists, though.
>> 281
>> 282 Many kernel-related lists are hosted on vger.kernel.org; you can find a
>> 283 list of them at http://vger.kernel.org/vger-lists.html. There are
>> 284 kernel-related lists hosted elsewhere as well, though.
233 285
234 You should always copy the appropriate subsyst !! 286 Do not send more than 15 patches at once to the vger mailing lists!!!
235 any patch to code that they maintain; look thr <<
236 source code revision history to see who those <<
237 scripts/get_maintainer.pl can be very useful a <<
238 patches as arguments to scripts/get_maintainer <<
239 maintainer for the subsystem you are working o <<
240 (akpm@linux-foundation.org) serves as a mainta <<
241 <<
242 linux-kernel@vger.kernel.org should be used by <<
243 volume on that list has caused a number of dev <<
244 do not spam unrelated lists and unrelated peop <<
245 <<
246 Many kernel-related lists are hosted at kernel <<
247 of them at https://subspace.kernel.org. There <<
248 hosted elsewhere as well, though. <<
249 287
250 Linus Torvalds is the final arbiter of all cha 288 Linus Torvalds is the final arbiter of all changes accepted into the
251 Linux kernel. His e-mail address is <torvalds@ 289 Linux kernel. His e-mail address is <torvalds@linux-foundation.org>.
252 He gets a lot of e-mail, and, at this point, v 290 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 291 Linus directly, so typically you should do your best to -avoid-
254 sending him e-mail. 292 sending him e-mail.
255 293
256 If you have a patch that fixes an exploitable 294 If you have a patch that fixes an exploitable security bug, send that patch
257 to security@kernel.org. For severe bugs, a sh 295 to security@kernel.org. For severe bugs, a short embargo may be considered
258 to allow distributors to get the patch out to 296 to allow distributors to get the patch out to users; in such cases,
259 obviously, the patch should not be sent to any !! 297 obviously, the patch should not be sent to any public lists.
260 Documentation/process/security-bugs.rst. <<
261 298
262 Patches that fix a severe bug in a released ke 299 Patches that fix a severe bug in a released kernel should be directed
263 toward the stable maintainers by putting a lin 300 toward the stable maintainers by putting a line like this::
264 301
265 Cc: stable@vger.kernel.org 302 Cc: stable@vger.kernel.org
266 303
267 into the sign-off area of your patch (note, NO 304 into the sign-off area of your patch (note, NOT an email recipient). You
268 should also read Documentation/process/stable- !! 305 should also read
269 in addition to this document. !! 306 :ref:`Documentation/process/stable-kernel-rules.rst <stable_kernel_rules>`
>> 307 in addition to this file.
>> 308
>> 309 Note, however, that some subsystem maintainers want to come to their own
>> 310 conclusions on which patches should go to the stable trees. The networking
>> 311 maintainer, in particular, would rather not see individual developers
>> 312 adding lines like the above to their patches.
270 313
271 If changes affect userland-kernel interfaces, 314 If changes affect userland-kernel interfaces, please send the MAN-PAGES
272 maintainer (as listed in the MAINTAINERS file) 315 maintainer (as listed in the MAINTAINERS file) a man-pages patch, or at
273 least a notification of the change, so that so 316 least a notification of the change, so that some information makes its way
274 into the manual pages. User-space API changes 317 into the manual pages. User-space API changes should also be copied to
275 linux-api@vger.kernel.org. 318 linux-api@vger.kernel.org.
276 319
>> 320 For small patches you may want to CC the Trivial Patch Monkey
>> 321 trivial@kernel.org which collects "trivial" patches. Have a look
>> 322 into the MAINTAINERS file for its current manager.
>> 323
>> 324 Trivial patches must qualify for one of the following rules:
>> 325
>> 326 - Spelling fixes in documentation
>> 327 - Spelling fixes for errors which could break :manpage:`grep(1)`
>> 328 - Warning fixes (cluttering with useless warnings is bad)
>> 329 - Compilation fixes (only if they are actually correct)
>> 330 - Runtime fixes (only if they actually fix things)
>> 331 - Removing use of deprecated functions/macros
>> 332 - Contact detail and documentation fixes
>> 333 - Non-portable code replaced by portable code (even in arch-specific,
>> 334 since people copy, as long as it's trivial)
>> 335 - Any fix by the author/maintainer of the file (ie. patch monkey
>> 336 in re-transmission mode)
277 337
278 No MIME, no links, no compression, no attachme !! 338
279 ---------------------------------------------- !! 339
>> 340 6) No MIME, no links, no compression, no attachments. Just plain text
>> 341 ----------------------------------------------------------------------
280 342
281 Linus and other kernel developers need to be a 343 Linus and other kernel developers need to be able to read and comment
282 on the changes you are submitting. It is impo 344 on the changes you are submitting. It is important for a kernel
283 developer to be able to "quote" your changes, 345 developer to be able to "quote" your changes, using standard e-mail
284 tools, so that they may comment on specific po 346 tools, so that they may comment on specific portions of your code.
285 347
286 For this reason, all patches should be submitt !! 348 For this reason, all patches should be submitted by e-mail "inline".
287 easiest way to do this is with ``git send-emai <<
288 recommended. An interactive tutorial for ``gi <<
289 https://git-send-email.io. <<
290 <<
291 If you choose not to use ``git send-email``: <<
292 349
293 .. warning:: 350 .. warning::
294 351
295 Be wary of your editor's word-wrap corruptin 352 Be wary of your editor's word-wrap corrupting your patch,
296 if you choose to cut-n-paste your patch. 353 if you choose to cut-n-paste your patch.
297 354
298 Do not attach the patch as a MIME attachment, 355 Do not attach the patch as a MIME attachment, compressed or not.
299 Many popular e-mail applications will not alwa 356 Many popular e-mail applications will not always transmit a MIME
300 attachment as plain text, making it impossible 357 attachment as plain text, making it impossible to comment on your
301 code. A MIME attachment also takes Linus a bi 358 code. A MIME attachment also takes Linus a bit more time to process,
302 decreasing the likelihood of your MIME-attache 359 decreasing the likelihood of your MIME-attached change being accepted.
303 360
304 Exception: If your mailer is mangling patches 361 Exception: If your mailer is mangling patches then someone may ask
305 you to re-send them using MIME. 362 you to re-send them using MIME.
306 363
307 See Documentation/process/email-clients.rst fo !! 364 See :ref:`Documentation/process/email-clients.rst <email_clients>`
308 your e-mail client so that it sends your patch !! 365 for hints about configuring your e-mail client so that it sends your patches
>> 366 untouched.
>> 367
>> 368 7) E-mail size
>> 369 --------------
>> 370
>> 371 Large changes are not appropriate for mailing lists, and some
>> 372 maintainers. If your patch, uncompressed, exceeds 300 kB in size,
>> 373 it is preferred that you store your patch on an Internet-accessible
>> 374 server, and provide instead a URL (link) pointing to your patch. But note
>> 375 that if your patch exceeds 300 kB, it almost certainly needs to be broken up
>> 376 anyway.
309 377
310 Respond to review comments !! 378 8) Respond to review comments
311 -------------------------- !! 379 -----------------------------
312 380
313 Your patch will almost certainly get comments 381 Your patch will almost certainly get comments from reviewers on ways in
314 which the patch can be improved, in the form o !! 382 which the patch can be improved. You must respond to those comments;
315 respond to those comments; ignoring reviewers !! 383 ignoring reviewers is a good way to get ignored in return. Review comments
316 return. You can simply reply to their emails t !! 384 or questions that do not lead to a code change should almost certainly
317 comments or questions that do not lead to a co <<
318 bring about a comment or changelog entry so th 385 bring about a comment or changelog entry so that the next reviewer better
319 understands what is going on. 386 understands what is going on.
320 387
321 Be sure to tell the reviewers what changes you 388 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 389 for their time. Code review is a tiring and time-consuming process, and
323 reviewers sometimes get grumpy. Even in that 390 reviewers sometimes get grumpy. Even in that case, though, respond
324 politely and address the problems they have po !! 391 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 <<
331 See Documentation/process/email-clients.rst fo <<
332 clients and mailing list etiquette. <<
333 <<
334 .. _interleaved_replies: <<
335 <<
336 Use trimmed interleaved replies in email discu <<
337 ---------------------------------------------- <<
338 Top-posting is strongly discouraged in Linux k <<
339 discussions. Interleaved (or "inline") replies <<
340 easier to follow. For more details see: <<
341 https://en.wikipedia.org/wiki/Posting_style#In <<
342 <<
343 As is frequently quoted on the mailing list:: <<
344 <<
345 A: http://en.wikipedia.org/wiki/Top_post <<
346 Q: Were do I find info about this thing call <<
347 A: Because it messes up the order in which p <<
348 Q: Why is top-posting such a bad thing? <<
349 A: Top-posting. <<
350 Q: What is the most annoying thing in e-mail <<
351 <<
352 Similarly, please trim all unneeded quotations <<
353 to your reply. This makes responses easier to <<
354 space. For more details see: http://daringfire <<
355 <<
356 A: No. <<
357 Q: Should I include quotations after my repl <<
358 392
359 .. _resend_reminders: <<
360 393
361 Don't get discouraged - or impatient !! 394 9) Don't get discouraged - or impatient
362 ------------------------------------ !! 395 ---------------------------------------
363 396
364 After you have submitted your change, be patie 397 After you have submitted your change, be patient and wait. Reviewers are
365 busy people and may not get to your patch righ 398 busy people and may not get to your patch right away.
366 399
367 Once upon a time, patches used to disappear in 400 Once upon a time, patches used to disappear into the void without comment,
368 but the development process works more smoothl 401 but the development process works more smoothly than that now. You should
369 receive comments within a few weeks (typically !! 402 receive comments within a week or so; if that does not happen, make sure
370 happen, make sure that you have sent your patc !! 403 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 !! 404 one week before resubmitting or pinging reviewers - possibly longer during
372 - possibly longer during busy times like merge !! 405 busy times like merge windows.
373 <<
374 It's also ok to resend the patch or the patch <<
375 weeks with the word "RESEND" added to the subj <<
376 <<
377 [PATCH Vx RESEND] sub/sys: Condensed patch <<
378 406
379 Don't add "RESEND" when you are submitting a m <<
380 patch or patch series - "RESEND" only applies <<
381 patch or patch series which have not been modi <<
382 previous submission. <<
383 407
384 !! 408 10) Include PATCH in the subject
385 Include PATCH in the subject !! 409 --------------------------------
386 ----------------------------- <<
387 410
388 Due to high e-mail traffic to Linus, and to li 411 Due to high e-mail traffic to Linus, and to linux-kernel, it is common
389 convention to prefix your subject line with [P 412 convention to prefix your subject line with [PATCH]. This lets Linus
390 and other kernel developers more easily distin 413 and other kernel developers more easily distinguish patches from other
391 e-mail discussions. 414 e-mail discussions.
392 415
393 ``git send-email`` will do this for you automa <<
394 416
395 417
396 Sign your work - the Developer's Certificate o !! 418 11) Sign your work - the Developer's Certificate of Origin
397 ---------------------------------------------- !! 419 ----------------------------------------------------------
398 420
399 To improve tracking of who did what, especiall 421 To improve tracking of who did what, especially with patches that can
400 percolate to their final resting place in the 422 percolate to their final resting place in the kernel through several
401 layers of maintainers, we've introduced a "sig 423 layers of maintainers, we've introduced a "sign-off" procedure on
402 patches that are being emailed around. 424 patches that are being emailed around.
403 425
404 The sign-off is a simple line at the end of th 426 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 427 patch, which certifies that you wrote it or otherwise have the right to
406 pass it on as an open-source patch. The rules 428 pass it on as an open-source patch. The rules are pretty simple: if you
407 can certify the below: 429 can certify the below:
408 430
409 Developer's Certificate of Origin 1.1 431 Developer's Certificate of Origin 1.1
410 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 432 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
411 433
412 By making a contribution to this project, I ce 434 By making a contribution to this project, I certify that:
413 435
414 (a) The contribution was created in wh 436 (a) The contribution was created in whole or in part by me and I
415 have the right to submit it under 437 have the right to submit it under the open source license
416 indicated in the file; or 438 indicated in the file; or
417 439
418 (b) The contribution is based upon pre 440 (b) The contribution is based upon previous work that, to the best
419 of my knowledge, is covered under 441 of my knowledge, is covered under an appropriate open source
420 license and I have the right under 442 license and I have the right under that license to submit that
421 work with modifications, whether c 443 work with modifications, whether created in whole or in part
422 by me, under the same open source 444 by me, under the same open source license (unless I am
423 permitted to submit under a differ 445 permitted to submit under a different license), as indicated
424 in the file; or 446 in the file; or
425 447
426 (c) The contribution was provided dire 448 (c) The contribution was provided directly to me by some other
427 person who certified (a), (b) or ( 449 person who certified (a), (b) or (c) and I have not modified
428 it. 450 it.
429 451
430 (d) I understand and agree that this p 452 (d) I understand and agree that this project and the contribution
431 are public and that a record of th 453 are public and that a record of the contribution (including all
432 personal information I submit with 454 personal information I submit with it, including my sign-off) is
433 maintained indefinitely and may be 455 maintained indefinitely and may be redistributed consistent with
434 this project or the open source li 456 this project or the open source license(s) involved.
435 457
436 then you just add a line saying:: 458 then you just add a line saying::
437 459
438 Signed-off-by: Random J Developer <rand 460 Signed-off-by: Random J Developer <random@developer.example.org>
439 461
440 using a known identity (sorry, no anonymous co !! 462 using your real name (sorry, no pseudonyms or anonymous contributions.)
441 This will be done for you automatically if you <<
442 Reverts should also include "Signed-off-by". ` <<
443 for you. <<
444 463
445 Some people also put extra tags at the end. T 464 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 465 now, but you can do this to mark internal company procedures or just
447 point out some special detail about the sign-o 466 point out some special detail about the sign-off.
448 467
449 Any further SoBs (Signed-off-by:'s) following !! 468 If you are a subsystem or branch maintainer, sometimes you need to slightly
450 people handling and transporting the patch, bu !! 469 modify patches you receive in order to merge them, because the code is not
451 development. SoB chains should reflect the **r !! 470 exactly the same in your tree and the submitters'. If you stick strictly to
452 as it was propagated to the maintainers and ul !! 471 rule (c), you should ask the submitter to rediff, but this is a totally
453 the first SoB entry signalling primary authors !! 472 counter-productive waste of time and energy. Rule (b) allows you to adjust
>> 473 the code, but then it is very impolite to change one submitter's code and
>> 474 make him endorse your bugs. To solve this problem, it is recommended that
>> 475 you add a line between the last Signed-off-by header and yours, indicating
>> 476 the nature of your changes. While there is nothing mandatory about this, it
>> 477 seems like prepending the description with your mail and/or name, all
>> 478 enclosed in square brackets, is noticeable enough to make it obvious that
>> 479 you are responsible for last-minute changes. Example::
>> 480
>> 481 Signed-off-by: Random J Developer <random@developer.example.org>
>> 482 [lucky@maintainer.example.org: struct foo moved from foo.c to foo.h]
>> 483 Signed-off-by: Lucky K Maintainer <lucky@maintainer.example.org>
>> 484
>> 485 This practice is particularly helpful if you maintain a stable branch and
>> 486 want at the same time to credit the author, track changes, merge the fix,
>> 487 and protect the submitter from complaints. Note that under no circumstances
>> 488 can you change the author's identity (the From header), as it is the one
>> 489 which appears in the changelog.
>> 490
>> 491 Special note to back-porters: It seems to be a common and useful practice
>> 492 to insert an indication of the origin of a patch at the top of the commit
>> 493 message (just after the subject line) to facilitate tracking. For instance,
>> 494 here's what we see in a 3.x-stable release::
>> 495
>> 496 Date: Tue Oct 7 07:26:38 2014 -0400
>> 497
>> 498 libata: Un-break ATA blacklist
>> 499
>> 500 commit 1c40279960bcd7d52dbdf1d466b20d24b99176c8 upstream.
454 501
>> 502 And here's what might appear in an older kernel once a patch is backported::
455 503
456 When to use Acked-by:, Cc:, and Co-developed-b !! 504 Date: Tue May 13 22:12:27 2008 +0200
457 ---------------------------------------------- !! 505
>> 506 wireless, airo: waitbusy() won't delay
>> 507
>> 508 [backport of 2.6 commit b7acbdfbd1f277c1eb23f344f899cfa4cd0bf36a]
>> 509
>> 510 Whatever the format, this information provides a valuable help to people
>> 511 tracking your trees, and to people trying to troubleshoot bugs in your
>> 512 tree.
>> 513
>> 514
>> 515 12) When to use Acked-by:, Cc:, and Co-developed-by:
>> 516 -------------------------------------------------------
458 517
459 The Signed-off-by: tag indicates that the sign 518 The Signed-off-by: tag indicates that the signer was involved in the
460 development of the patch, or that he/she was i 519 development of the patch, or that he/she was in the patch's delivery path.
461 520
462 If a person was not directly involved in the p 521 If a person was not directly involved in the preparation or handling of a
463 patch but wishes to signify and record their a 522 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 523 ask to have an Acked-by: line added to the patch's changelog.
465 524
466 Acked-by: is often used by the maintainer of t 525 Acked-by: is often used by the maintainer of the affected code when that
467 maintainer neither contributed to nor forwarde 526 maintainer neither contributed to nor forwarded the patch.
468 527
469 Acked-by: is not as formal as Signed-off-by:. 528 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 529 has at least reviewed the patch and has indicated acceptance. Hence patch
471 mergers will sometimes manually convert an ack 530 mergers will sometimes manually convert an acker's "yep, looks good to me"
472 into an Acked-by: (but note that it is usually 531 into an Acked-by: (but note that it is usually better to ask for an
473 explicit ack). 532 explicit ack).
474 533
475 Acked-by: does not necessarily indicate acknow 534 Acked-by: does not necessarily indicate acknowledgement of the entire patch.
476 For example, if a patch affects multiple subsy 535 For example, if a patch affects multiple subsystems and has an Acked-by: from
477 one subsystem maintainer then this usually ind 536 one subsystem maintainer then this usually indicates acknowledgement of just
478 the part which affects that maintainer's code. 537 the part which affects that maintainer's code. Judgement should be used here.
479 When in doubt people should refer to the origi 538 When in doubt people should refer to the original discussion in the mailing
480 list archives. 539 list archives.
481 540
482 If a person has had the opportunity to comment 541 If a person has had the opportunity to comment on a patch, but has not
483 provided such comments, you may optionally add 542 provided such comments, you may optionally add a ``Cc:`` tag to the patch.
484 This is the only tag which might be added with 543 This is the only tag which might be added without an explicit action by the
485 person it names - but it should indicate that 544 person it names - but it should indicate that this person was copied on the
486 patch. This tag documents that potentially in 545 patch. This tag documents that potentially interested parties
487 have been included in the discussion. 546 have been included in the discussion.
488 547
489 Co-developed-by: states that the patch was co- !! 548 A Co-developed-by: states that the patch was also created by another developer
490 it is used to give attribution to co-authors ( !! 549 along with the original author. This is useful at times when multiple people
491 attributed by the From: tag) when several peop !! 550 work on a single patch. Note, this person also needs to have a Signed-off-by:
492 Co-developed-by: denotes authorship, every Co- !! 551 line in the patch as well.
493 followed by a Signed-off-by: of the associated <<
494 procedure applies, i.e. the ordering of Signed <<
495 chronological history of the patch insofar as <<
496 the author is attributed via From: or Co-devel <<
497 Signed-off-by: must always be that of the deve <<
498 <<
499 Note, the From: tag is optional when the From: <<
500 email) listed in the From: line of the email h <<
501 <<
502 Example of a patch submitted by the From: auth <<
503 <<
504 <changelog> <<
505 <<
506 Co-developed-by: First Co-Author <first <<
507 Signed-off-by: First Co-Author <first@c <<
508 Co-developed-by: Second Co-Author <seco <<
509 Signed-off-by: Second Co-Author <second <<
510 Signed-off-by: From Author <from@author <<
511 552
512 Example of a patch submitted by a Co-developed <<
513 553
514 From: From Author <from@author.example. !! 554 13) Using Reported-by:, Tested-by:, Reviewed-by:, Suggested-by: and Fixes:
515 !! 555 --------------------------------------------------------------------------
516 <changelog> <<
517 <<
518 Co-developed-by: Random Co-Author <rand <<
519 Signed-off-by: Random Co-Author <random <<
520 Signed-off-by: From Author <from@author <<
521 Co-developed-by: Submitting Co-Author < <<
522 Signed-off-by: Submitting Co-Author <su <<
523 <<
524 <<
525 Using Reported-by:, Tested-by:, Reviewed-by:, <<
526 ---------------------------------------------- <<
527 556
528 The Reported-by tag gives credit to people who 557 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 !! 558 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 !! 559 the bug was reported in private, then ask for permission first before using the
531 followed by a Closes: tag pointing to the repo !! 560 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. <<
536 561
537 A Tested-by: tag indicates that the patch has 562 A Tested-by: tag indicates that the patch has been successfully tested (in
538 some environment) by the person named. This t 563 some environment) by the person named. This tag informs maintainers that
539 some testing has been performed, provides a me 564 some testing has been performed, provides a means to locate testers for
540 future patches, and ensures credit for the tes 565 future patches, and ensures credit for the testers.
541 566
542 Reviewed-by:, instead, indicates that the patc 567 Reviewed-by:, instead, indicates that the patch has been reviewed and found
543 acceptable according to the Reviewer's Stateme 568 acceptable according to the Reviewer's Statement:
544 569
545 Reviewer's statement of oversight 570 Reviewer's statement of oversight
546 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 571 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
547 572
548 By offering my Reviewed-by: tag, I state that: 573 By offering my Reviewed-by: tag, I state that:
549 574
550 (a) I have carried out a technical re 575 (a) I have carried out a technical review of this patch to
551 evaluate its appropriateness and 576 evaluate its appropriateness and readiness for inclusion into
552 the mainline kernel. 577 the mainline kernel.
553 578
554 (b) Any problems, concerns, or questi 579 (b) Any problems, concerns, or questions relating to the patch
555 have been communicated back to th 580 have been communicated back to the submitter. I am satisfied
556 with the submitter's response to 581 with the submitter's response to my comments.
557 582
558 (c) While there may be things that co 583 (c) While there may be things that could be improved with this
559 submission, I believe that it is, 584 submission, I believe that it is, at this time, (1) a
560 worthwhile modification to the ke 585 worthwhile modification to the kernel, and (2) free of known
561 issues which would argue against 586 issues which would argue against its inclusion.
562 587
563 (d) While I have reviewed the patch a 588 (d) While I have reviewed the patch and believe it to be sound, I
564 do not (unless explicitly stated 589 do not (unless explicitly stated elsewhere) make any
565 warranties or guarantees that it 590 warranties or guarantees that it will achieve its stated
566 purpose or function properly in a 591 purpose or function properly in any given situation.
567 592
568 A Reviewed-by tag is a statement of opinion th 593 A Reviewed-by tag is a statement of opinion that the patch is an
569 appropriate modification of the kernel without 594 appropriate modification of the kernel without any remaining serious
570 technical issues. Any interested reviewer (wh 595 technical issues. Any interested reviewer (who has done the work) can
571 offer a Reviewed-by tag for a patch. This tag 596 offer a Reviewed-by tag for a patch. This tag serves to give credit to
572 reviewers and to inform maintainers of the deg 597 reviewers and to inform maintainers of the degree of review which has been
573 done on the patch. Reviewed-by: tags, when su 598 done on the patch. Reviewed-by: tags, when supplied by reviewers known to
574 understand the subject area and to perform tho 599 understand the subject area and to perform thorough reviews, will normally
575 increase the likelihood of your patch getting 600 increase the likelihood of your patch getting into the kernel.
576 601
577 Both Tested-by and Reviewed-by tags, once rece <<
578 or reviewer, should be added by author to the <<
579 next versions. However if the patch has chang <<
580 version, these tags might not be applicable an <<
581 Usually removal of someone's Tested-by or Revi <<
582 in the patch changelog (after the '---' separa <<
583 <<
584 A Suggested-by: tag indicates that the patch i 602 A Suggested-by: tag indicates that the patch idea is suggested by the person
585 named and ensures credit to the person for the 603 named and ensures credit to the person for the idea. Please note that this
586 tag should not be added without the reporter's 604 tag should not be added without the reporter's permission, especially if the
587 idea was not posted in a public forum. That sa 605 idea was not posted in a public forum. That said, if we diligently credit our
588 idea reporters, they will, hopefully, be inspi 606 idea reporters, they will, hopefully, be inspired to help us again in the
589 future. 607 future.
590 608
591 A Fixes: tag indicates that the patch fixes an 609 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 610 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 611 review a bug fix. This tag also assists the stable kernel team in determining
594 which stable kernel versions should receive yo 612 which stable kernel versions should receive your fix. This is the preferred
595 method for indicating a bug fixed by the patch 613 method for indicating a bug fixed by the patch. See :ref:`describe_changes`
596 for more details. 614 for more details.
597 615
598 Note: Attaching a Fixes: tag does not subvert <<
599 process nor the requirement to Cc: stable@vger <<
600 patch candidates. For more information, please <<
601 Documentation/process/stable-kernel-rules.rst. <<
602 <<
603 .. _the_canonical_patch_format: 616 .. _the_canonical_patch_format:
604 617
605 The canonical patch format !! 618 14) The canonical patch format
606 -------------------------- !! 619 ------------------------------
607 620
608 This section describes how the patch itself sh 621 This section describes how the patch itself should be formatted. Note
609 that, if you have your patches stored in a ``g 622 that, if you have your patches stored in a ``git`` repository, proper patch
610 formatting can be had with ``git format-patch` 623 formatting can be had with ``git format-patch``. The tools cannot create
611 the necessary text, though, so read the instru 624 the necessary text, though, so read the instructions below anyway.
612 625
613 The canonical patch subject line is:: 626 The canonical patch subject line is::
614 627
615 Subject: [PATCH 001/123] subsystem: summar 628 Subject: [PATCH 001/123] subsystem: summary phrase
616 629
617 The canonical patch message body contains the 630 The canonical patch message body contains the following:
618 631
619 - A ``from`` line specifying the patch autho 632 - A ``from`` line specifying the patch author, followed by an empty
620 line (only needed if the person sending th 633 line (only needed if the person sending the patch is not the author).
621 634
622 - The body of the explanation, line wrapped 635 - The body of the explanation, line wrapped at 75 columns, which will
623 be copied to the permanent changelog to de 636 be copied to the permanent changelog to describe this patch.
624 637
625 - An empty line. 638 - An empty line.
626 639
627 - The ``Signed-off-by:`` lines, described ab 640 - The ``Signed-off-by:`` lines, described above, which will
628 also go in the changelog. 641 also go in the changelog.
629 642
630 - A marker line containing simply ``---``. 643 - A marker line containing simply ``---``.
631 644
632 - Any additional comments not suitable for t 645 - Any additional comments not suitable for the changelog.
633 646
634 - The actual patch (``diff`` output). 647 - The actual patch (``diff`` output).
635 648
636 The Subject line format makes it very easy to 649 The Subject line format makes it very easy to sort the emails
637 alphabetically by subject line - pretty much a 650 alphabetically by subject line - pretty much any email reader will
638 support that - since because the sequence numb 651 support that - since because the sequence number is zero-padded,
639 the numerical and alphabetic sort is the same. 652 the numerical and alphabetic sort is the same.
640 653
641 The ``subsystem`` in the email's Subject shoul 654 The ``subsystem`` in the email's Subject should identify which
642 area or subsystem of the kernel is being patch 655 area or subsystem of the kernel is being patched.
643 656
644 The ``summary phrase`` in the email's Subject 657 The ``summary phrase`` in the email's Subject should concisely
645 describe the patch which that email contains. 658 describe the patch which that email contains. The ``summary
646 phrase`` should not be a filename. Do not use 659 phrase`` should not be a filename. Do not use the same ``summary
647 phrase`` for every patch in a whole patch seri 660 phrase`` for every patch in a whole patch series (where a ``patch
648 series`` is an ordered sequence of multiple, r 661 series`` is an ordered sequence of multiple, related patches).
649 662
650 Bear in mind that the ``summary phrase`` of yo 663 Bear in mind that the ``summary phrase`` of your email becomes a
651 globally-unique identifier for that patch. It 664 globally-unique identifier for that patch. It propagates all the way
652 into the ``git`` changelog. The ``summary phr 665 into the ``git`` changelog. The ``summary phrase`` may later be used in
653 developer discussions which refer to the patch 666 developer discussions which refer to the patch. People will want to
654 google for the ``summary phrase`` to read disc 667 google for the ``summary phrase`` to read discussion regarding that
655 patch. It will also be the only thing that pe 668 patch. It will also be the only thing that people may quickly see
656 when, two or three months later, they are goin 669 when, two or three months later, they are going through perhaps
657 thousands of patches using tools such as ``git 670 thousands of patches using tools such as ``gitk`` or ``git log
658 --oneline``. 671 --oneline``.
659 672
660 For these reasons, the ``summary`` must be no 673 For these reasons, the ``summary`` must be no more than 70-75
661 characters, and it must describe both what the 674 characters, and it must describe both what the patch changes, as well
662 as why the patch might be necessary. It is ch 675 as why the patch might be necessary. It is challenging to be both
663 succinct and descriptive, but that is what a w 676 succinct and descriptive, but that is what a well-written summary
664 should do. 677 should do.
665 678
666 The ``summary phrase`` may be prefixed by tags 679 The ``summary phrase`` may be prefixed by tags enclosed in square
667 brackets: "Subject: [PATCH <tag>...] <summary 680 brackets: "Subject: [PATCH <tag>...] <summary phrase>". The tags are
668 not considered part of the summary phrase, but 681 not considered part of the summary phrase, but describe how the patch
669 should be treated. Common tags might include 682 should be treated. Common tags might include a version descriptor if
670 the multiple versions of the patch have been s 683 the multiple versions of the patch have been sent out in response to
671 comments (i.e., "v1, v2, v3"), or "RFC" to ind 684 comments (i.e., "v1, v2, v3"), or "RFC" to indicate a request for
672 comments. !! 685 comments. If there are four patches in a patch series the individual
>> 686 patches may be numbered like this: 1/4, 2/4, 3/4, 4/4. This assures
>> 687 that developers understand the order in which the patches should be
>> 688 applied and that they have reviewed or applied all of the patches in
>> 689 the patch series.
673 690
674 If there are four patches in a patch series th !! 691 A couple of example Subjects::
675 be numbered like this: 1/4, 2/4, 3/4, 4/4. Thi <<
676 understand the order in which the patches shou <<
677 they have reviewed or applied all of the patch <<
678 <<
679 Here are some good example Subjects:: <<
680 692
681 Subject: [PATCH 2/5] ext2: improve scalabi 693 Subject: [PATCH 2/5] ext2: improve scalability of bitmap searching
682 Subject: [PATCH v2 01/27] x86: fix eflags 694 Subject: [PATCH v2 01/27] x86: fix eflags tracking
683 Subject: [PATCH v2] sub/sys: Condensed pat <<
684 Subject: [PATCH v2 M/N] sub/sys: Condensed <<
685 695
686 The ``from`` line must be the very first line 696 The ``from`` line must be the very first line in the message body,
687 and has the form: 697 and has the form:
688 698
689 From: Patch Author <author@example.com> !! 699 From: Original Author <author@example.com>
690 700
691 The ``from`` line specifies who will be credit 701 The ``from`` line specifies who will be credited as the author of the
692 patch in the permanent changelog. If the ``fr 702 patch in the permanent changelog. If the ``from`` line is missing,
693 then the ``From:`` line from the email header 703 then the ``From:`` line from the email header will be used to determine
694 the patch author in the changelog. 704 the patch author in the changelog.
695 705
696 The explanation body will be committed to the 706 The explanation body will be committed to the permanent source
697 changelog, so should make sense to a competent !! 707 changelog, so should make sense to a competent reader who has long
698 forgotten the immediate details of the discuss !! 708 since forgotten the immediate details of the discussion that might
699 this patch. Including symptoms of the failure !! 709 have led to this patch. Including symptoms of the failure which the
700 (kernel log messages, oops messages, etc.) are !! 710 patch addresses (kernel log messages, oops messages, etc.) is
701 people who might be searching the commit logs !! 711 especially useful for people who might be searching the commit logs
702 patch. The text should be written in such deta !! 712 looking for the applicable patch. If a patch fixes a compile failure,
703 weeks, months or even years later, it can give !! 713 it may not be necessary to include _all_ of the compile failures; just
704 details to grasp the reasoning for **why** the !! 714 enough that it is likely that someone searching for the patch can find
705 !! 715 it. As in the ``summary phrase``, it is important to be both succinct as
706 If a patch fixes a compile failure, it may not !! 716 well as descriptive.
707 _all_ of the compile failures; just enough tha !! 717
708 someone searching for the patch can find it. A !! 718 The ``---`` marker line serves the essential purpose of marking for patch
709 phrase``, it is important to be both succinct !! 719 handling tools where the changelog message ends.
710 !! 720
711 The ``---`` marker line serves the essential p !! 721 One good use for the additional comments after the ``---`` marker is for
712 patch handling tools where the changelog messa !! 722 a ``diffstat``, to show what files have changed, and the number of
713 !! 723 inserted and deleted lines per file. A ``diffstat`` is especially useful
714 One good use for the additional comments after !! 724 on bigger patches. Other comments relevant only to the moment or the
715 for a ``diffstat``, to show what files have ch !! 725 maintainer, not suitable for the permanent changelog, should also go
716 inserted and deleted lines per file. A ``diffs !! 726 here. A good example of such comments might be ``patch changelogs``
717 on bigger patches. If you are going to include !! 727 which describe what has changed between the v1 and v2 version of the
718 ``---`` marker, please use ``diffstat`` option !! 728 patch.
719 filenames are listed from the top of the kerne <<
720 use too much horizontal space (easily fit in 8 <<
721 indentation). (``git`` generates appropriate d <<
722 <<
723 Other comments relevant only to the moment or <<
724 suitable for the permanent changelog, should a <<
725 example of such comments might be ``patch chan <<
726 what has changed between the v1 and v2 version <<
727 <<
728 Please put this information **after** the ``-- <<
729 the changelog from the rest of the patch. The <<
730 not part of the changelog which gets committed <<
731 additional information for the reviewers. If i <<
732 commit tags, it needs manual interaction to re <<
733 the separator line, it gets automatically stri <<
734 patch:: <<
735 <<
736 <commit message> <<
737 ... <<
738 Signed-off-by: Author <author@mail> <<
739 --- <<
740 V2 -> V3: Removed redundant helper function <<
741 V1 -> V2: Cleaned up coding style and addres <<
742 729
743 path/to/file | 5+++-- !! 730 If you are going to include a ``diffstat`` after the ``---`` marker, please
744 ... !! 731 use ``diffstat`` options ``-p 1 -w 70`` so that filenames are listed from
>> 732 the top of the kernel source tree and don't use too much horizontal
>> 733 space (easily fit in 80 columns, maybe with some indentation). (``git``
>> 734 generates appropriate diffstats by default.)
745 735
746 See more details on the proper patch format in 736 See more details on the proper patch format in the following
747 references. 737 references.
748 738
749 .. _backtraces: <<
750 <<
751 Backtraces in commit messages <<
752 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ <<
753 <<
754 Backtraces help document the call chain leadin <<
755 not all backtraces are helpful. For example, e <<
756 unique and obvious. Copying the full dmesg out <<
757 adds distracting information like timestamps, <<
758 stack dumps. <<
759 <<
760 Therefore, the most useful backtraces should d <<
761 information from the dump, which makes it easi <<
762 issue. Here is an example of a well-trimmed ba <<
763 <<
764 unchecked MSR access error: WRMSR to 0xd51 ( <<
765 at rIP: 0xffffffffae059994 (native_write_msr <<
766 Call Trace: <<
767 mba_wrmsr <<
768 update_domains <<
769 rdtgroup_mkdir <<
770 <<
771 .. _explicit_in_reply_to: 739 .. _explicit_in_reply_to:
772 740
773 Explicit In-Reply-To headers !! 741 15) Explicit In-Reply-To headers
774 ---------------------------- !! 742 --------------------------------
775 743
776 It can be helpful to manually add In-Reply-To: 744 It can be helpful to manually add In-Reply-To: headers to a patch
777 (e.g., when using ``git send-email``) to assoc 745 (e.g., when using ``git send-email``) to associate the patch with
778 previous relevant discussion, e.g. to link a b 746 previous relevant discussion, e.g. to link a bug fix to the email with
779 the bug report. However, for a multi-patch se 747 the bug report. However, for a multi-patch series, it is generally
780 best to avoid using In-Reply-To: to link to ol 748 best to avoid using In-Reply-To: to link to older versions of the
781 series. This way multiple versions of the pat 749 series. This way multiple versions of the patch don't become an
782 unmanageable forest of references in email cli 750 unmanageable forest of references in email clients. If a link is
783 helpful, you can use the https://lore.kernel.o !! 751 helpful, you can use the https://lkml.kernel.org/ redirector (e.g., in
784 the cover email text) to link to an earlier ve 752 the cover email text) to link to an earlier version of the patch series.
785 753
786 754
787 Providing base tree information !! 755 16) Sending ``git pull`` requests
788 ------------------------------- !! 756 ---------------------------------
>> 757
>> 758 If you have a series of patches, it may be most convenient to have the
>> 759 maintainer pull them directly into the subsystem repository with a
>> 760 ``git pull`` operation. Note, however, that pulling patches from a developer
>> 761 requires a higher degree of trust than taking patches from a mailing list.
>> 762 As a result, many subsystem maintainers are reluctant to take pull
>> 763 requests, especially from new, unknown developers. If in doubt you can use
>> 764 the pull request as the cover letter for a normal posting of the patch
>> 765 series, giving the maintainer the option of using either.
>> 766
>> 767 A pull request should have [GIT PULL] in the subject line. The
>> 768 request itself should include the repository name and the branch of
>> 769 interest on a single line; it should look something like::
>> 770
>> 771 Please pull from
>> 772
>> 773 git://jdelvare.pck.nerim.net/jdelvare-2.6 i2c-for-linus
>> 774
>> 775 to get these changes:
>> 776
>> 777 A pull request should also include an overall message saying what will be
>> 778 included in the request, a ``git shortlog`` listing of the patches
>> 779 themselves, and a ``diffstat`` showing the overall effect of the patch series.
>> 780 The easiest way to get all this information together is, of course, to let
>> 781 ``git`` do it for you with the ``git request-pull`` command.
>> 782
>> 783 Some maintainers (including Linus) want to see pull requests from signed
>> 784 commits; that increases their confidence that the request actually came
>> 785 from you. Linus, in particular, will not pull from public hosting sites
>> 786 like GitHub in the absence of a signed tag.
>> 787
>> 788 The first step toward creating such tags is to make a GNUPG key and get it
>> 789 signed by one or more core kernel developers. This step can be hard for
>> 790 new developers, but there is no way around it. Attending conferences can
>> 791 be a good way to find developers who can sign your key.
>> 792
>> 793 Once you have prepared a patch series in ``git`` that you wish to have somebody
>> 794 pull, create a signed tag with ``git tag -s``. This will create a new tag
>> 795 identifying the last commit in the series and containing a signature
>> 796 created with your private key. You will also have the opportunity to add a
>> 797 changelog-style message to the tag; this is an ideal place to describe the
>> 798 effects of the pull request as a whole.
>> 799
>> 800 If the tree the maintainer will be pulling from is not the repository you
>> 801 are working from, don't forget to push the signed tag explicitly to the
>> 802 public tree.
>> 803
>> 804 When generating your pull request, use the signed tag as the target. A
>> 805 command like this will do the trick::
>> 806
>> 807 git request-pull master git://my.public.tree/linux.git my-signed-tag
789 808
790 When other developers receive your patches and <<
791 it is absolutely necessary for them to know wh <<
792 commit/branch your work applies on, considerin <<
793 maintainer trees present nowadays. Note again <<
794 MAINTAINERS file explained above. <<
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 <<
800 If you are using ``git format-patch`` to gener <<
801 automatically include the base tree informatio <<
802 using the ``--base`` flag. The easiest and mos <<
803 this option is with topical branches:: <<
804 <<
805 $ git checkout -t -b my-topical-branch mas <<
806 Branch 'my-topical-branch' set up to track <<
807 Switched to a new branch 'my-topical-branc <<
808 <<
809 [perform your edits and commits] <<
810 <<
811 $ git format-patch --base=auto --cover-let <<
812 outgoing/0000-cover-letter.patch <<
813 outgoing/0001-First-Commit.patch <<
814 outgoing/... <<
815 <<
816 When you open ``outgoing/0000-cover-letter.pat <<
817 notice that it will have the ``base-commit:`` <<
818 bottom, which provides the reviewer and the CI <<
819 to properly perform ``git am`` without worryin <<
820 <<
821 $ git checkout -b patch-review [base-commi <<
822 Switched to a new branch 'patch-review' <<
823 $ git am patches.mbox <<
824 Applying: First Commit <<
825 Applying: ... <<
826 <<
827 Please see ``man git-format-patch`` for more i <<
828 option. <<
829 <<
830 .. note:: <<
831 <<
832 The ``--base`` feature was introduced in g <<
833 <<
834 If you are not using git to format your patche <<
835 the same ``base-commit`` trailer to indicate t <<
836 on which your work is based. You should add it <<
837 letter or in the first patch of the series and <<
838 either below the ``---`` line or at the very b <<
839 content, right before your email signature. <<
840 <<
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. <<
852 809
853 References 810 References
854 ---------- 811 ----------
855 812
856 Andrew Morton, "The perfect patch" (tpp). 813 Andrew Morton, "The perfect patch" (tpp).
857 <https://www.ozlabs.org/~akpm/stuff/tpp.txt> !! 814 <http://www.ozlabs.org/~akpm/stuff/tpp.txt>
858 815
859 Jeff Garzik, "Linux kernel patch submission fo 816 Jeff Garzik, "Linux kernel patch submission format".
860 <https://web.archive.org/web/20180829112450/ !! 817 <http://linux.yyz.us/patch-format.html>
861 818
862 Greg Kroah-Hartman, "How to piss off a kernel 819 Greg Kroah-Hartman, "How to piss off a kernel subsystem maintainer".
863 <http://www.kroah.com/log/linux/maintainer.h 820 <http://www.kroah.com/log/linux/maintainer.html>
864 821
865 <http://www.kroah.com/log/linux/maintainer-0 822 <http://www.kroah.com/log/linux/maintainer-02.html>
866 823
867 <http://www.kroah.com/log/linux/maintainer-0 824 <http://www.kroah.com/log/linux/maintainer-03.html>
868 825
869 <http://www.kroah.com/log/linux/maintainer-0 826 <http://www.kroah.com/log/linux/maintainer-04.html>
870 827
871 <http://www.kroah.com/log/linux/maintainer-0 828 <http://www.kroah.com/log/linux/maintainer-05.html>
872 829
873 <http://www.kroah.com/log/linux/maintainer-0 830 <http://www.kroah.com/log/linux/maintainer-06.html>
874 831
875 Kernel Documentation/process/coding-style.rst !! 832 NO!!!! No more huge patch bombs to linux-kernel@vger.kernel.org people!
>> 833 <https://lkml.org/lkml/2005/7/11/336>
>> 834
>> 835 Kernel Documentation/process/coding-style.rst:
>> 836 :ref:`Documentation/process/coding-style.rst <codingstyle>`
876 837
877 Linus Torvalds's mail on the canonical patch f 838 Linus Torvalds's mail on the canonical patch format:
878 <https://lore.kernel.org/r/Pine.LNX.4.58.0504 !! 839 <http://lkml.org/lkml/2005/4/7/183>
879 840
880 Andi Kleen, "On submitting kernel patches" 841 Andi Kleen, "On submitting kernel patches"
881 Some strategies to get difficult or controve 842 Some strategies to get difficult or controversial changes in.
882 843
883 http://halobates.de/on-submitting-patches.pd 844 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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