docs: move "stable" tag explanation next to `Fixes:`
[mesa.git] / docs / submittingpatches.rst
1 Submitting Patches
2 ==================
3
4 Basic guidelines
5 ----------------
6
7 - Patches should not mix code changes with code formatting changes
8 (except, perhaps, in very trivial cases.)
9 - Code patches should follow Mesa `coding
10 conventions <codingstyle.rst>`__.
11 - Whenever possible, patches should only affect individual Mesa/Gallium
12 components.
13 - Patches should never introduce build breaks and should be bisectable
14 (see ``git bisect``.)
15 - Patches should be properly `formatted <#formatting>`__.
16 - Patches should be sufficiently `tested <#testing>`__ before
17 submitting.
18 - Patches should be `submitted <#submit>`__ via a merge request for
19 `review <#reviewing>`__.
20
21 .. _formatting:
22
23 Patch formatting
24 ----------------
25
26 - Lines should be limited to 75 characters or less so that git logs
27 displayed in 80-column terminals avoid line wrapping. Note that git
28 log uses 4 spaces of indentation (4 + 75 < 80).
29 - The first line should be a short, concise summary of the change
30 prefixed with a module name. Examples:
31
32 ::
33
34 mesa: Add support for querying GL_VERTEX_ATTRIB_ARRAY_LONG
35
36 gallium: add PIPE_CAP_DEVICE_RESET_STATUS_QUERY
37
38 i965: Fix missing type in local variable declaration.
39
40 - Subsequent patch comments should describe the change in more detail,
41 if needed. For example:
42
43 ::
44
45 i965: Remove end-of-thread SEND alignment code.
46
47 This was present in Eric's initial implementation of the compaction code
48 for Sandybridge (commit 077d01b6). There is no documentation saying this
49 is necessary, and removing it causes no regressions in piglit on any
50 platform.
51
52 - A "Signed-off-by:" line is not required, but not discouraged either.
53 - If a patch addresses an issue in gitlab, use the Closes: tag For
54 example:
55
56 ::
57
58 Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/1
59
60 Prefer the full url to just ``Closes: #1``, since the url makes it
61 easier to get to the bug page from ``git log``
62
63 **Do not use the ``Fixes:`` tag for this!** Mesa already uses
64 ``Fixes:`` for something else.
65 See `below <#fixes>`__.
66
67 - If there have been several revisions to a patch during the review
68 process, they should be noted such as in this example:
69
70 ::
71
72 st/mesa: add ARB_texture_stencil8 support (v4)
73
74 if we support stencil texturing, enable texture_stencil8
75 there is no requirement to support native S8 for this,
76 the texture can be converted to x24s8 fine.
77
78 v2: fold fixes from Marek in:
79 a) put S8 last in the list
80 b) fix renderable to always test for d/s renderable
81 fixup the texture case to use a stencil only format
82 for picking the format for the texture view.
83 v3: hit fallback for getteximage
84 v4: put s8 back in front, it shouldn't get picked now (Ilia)
85
86 - If someone tested your patch, document it with a line like this:
87
88 ::
89
90 Tested-by: Joe Hacker <jhacker@foo.com>
91
92 - If the patch was reviewed (usually the case) or acked by someone,
93 that should be documented with:
94
95 ::
96
97 Reviewed-by: Joe Hacker <jhacker@foo.com>
98 Acked-by: Joe Hacker <jhacker@foo.com>
99
100 - When updating a merge request add all the tags (``Acked-by:``, ``Reviewed-by:``,
101 ``Fixes:``, ``Cc: mesa-stable`` and/or other) to the commit messages.
102 This provides reviewers with quick feedback if the patch has already
103 been reviewed.
104
105 .. _fixes:
106
107 The ``Fixes:`` tag
108 ------------------
109
110 If a patch addresses a issue introduced with earlier commit, that
111 should be noted in the commit message. For example::
112
113 Fixes: d7b3707c612 "util/disk_cache: use stat() to check if entry is a directory"
114
115 You can produce those fixes lines by running this command once::
116
117 git config --global alias.fixes "show -s --pretty='format:Fixes: %h (\"%s\")'"
118
119 After that, using ``git fixes <sha1>`` will print the full line for you.
120
121 The stable tag
122 ~~~~~~~~~~~~~~
123
124 If you want a commit to be applied to a stable branch, you should add an
125 appropriate note to the commit message.
126
127 Using a ``Fixes:`` tag as described in `Patch formatting <#formatting>`__
128 is the preferred way to nominate a commit that should be backported.
129 There are scripts that will figure out which releases to apply the patch
130 to automatically, so you don't need to figure it out.
131
132 Alternatively, you may use a "CC:" tag. Here are some examples of such a
133 note::
134
135 CC: 20.0 19.3 <mesa-stable>
136
137 Using the CC tag **should** include the stable branches you want to
138 nominate the patch to. If you do not provide any version it is nominated
139 to all active stable branches.
140
141 .. _testing:
142
143 Testing Patches
144 ---------------
145
146 It should go without saying that patches must be tested. In general, do
147 whatever testing is prudent.
148
149 You should always run the Mesa test suite before submitting patches. The
150 test suite can be run using the 'meson test' command. All tests must
151 pass before patches will be accepted, this may mean you have to update
152 the tests themselves.
153
154 Whenever possible and applicable, test the patch with
155 `Piglit <https://piglit.freedesktop.org>`__ and/or
156 `dEQP <https://android.googlesource.com/platform/external/deqp/>`__ to
157 check for regressions.
158
159 As mentioned at the beginning, patches should be bisectable. A good way
160 to test this is to make use of the \`git rebase\` command, to run your
161 tests on each commit. Assuming your branch is based off
162 ``origin/master``, you can run:
163
164 ::
165
166 $ git rebase --interactive --exec "meson test -C build/" origin/master
167
168 replacing ``"meson test"`` with whatever other test you want to run.
169
170 .. _submit:
171
172 Submitting Patches
173 ------------------
174
175 Patches are submitted to the Mesa project via a
176 `GitLab <https://gitlab.freedesktop.org/mesa/mesa>`__ Merge Request.
177
178 Add labels to your MR to help reviewers find it. For example:
179
180 - Mesa changes affecting all drivers: mesa
181 - Hardware vendor specific code: amd, intel, nvidia, ...
182 - Driver specific code: anvil, freedreno, i965, iris, radeonsi, radv,
183 vc4, ...
184 - Other tag examples: gallium, util
185
186 Tick the following when creating the MR. It allows developers to rebase
187 your work on top of master.
188
189 ::
190
191 Allow commits from members who can merge to the target branch
192
193 If you revise your patches based on code review and push an update to
194 your branch, you should maintain a **clean** history in your patches.
195 There should not be "fixup" patches in the history. The series should be
196 buildable and functional after every commit whenever you push the
197 branch.
198
199 It is your responsibility to keep the MR alive and making progress, as
200 there are no guarantees that a Mesa dev will independently take interest
201 in it.
202
203 Some other notes:
204
205 - Make changes and update your branch based on feedback
206 - After an update, for the feedback you handled, close the feedback
207 discussion with the "Resolve Discussion" button. This way the
208 reviewers know which feedback got handled and which didn't.
209 - Old, stale MR may be closed, but you can reopen it if you still want
210 to pursue the changes
211 - You should periodically check to see if your MR needs to be rebased
212 - Make sure your MR is closed if your patches get pushed outside of
213 GitLab
214 - Please send MRs from a personal fork rather than from the main Mesa
215 repository, as it clutters it unnecessarily.
216
217 .. _reviewing:
218
219 Reviewing Patches
220 -----------------
221
222 To participate in code review, you can monitor the GitLab Mesa `Merge
223 Requests <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests>`__
224 page, and/or register for notifications in your gitlab settings.
225
226 When you've reviewed a patch, please be unambiguous about your review.
227 That is, state either
228
229 ::
230
231 Reviewed-by: Joe Hacker <jhacker@foo.com>
232
233 or
234
235 ::
236
237 Acked-by: Joe Hacker <jhacker@foo.com>
238
239 Rather than saying just "LGTM" or "Seems OK".
240
241 If small changes are suggested, it's OK to say something like:
242
243 ::
244
245 With the above fixes, Reviewed-by: Joe Hacker <jhacker@foo.com>
246
247 which tells the patch author that the patch can be committed, as long as
248 the issues are resolved first.
249
250 These Reviewed-by, Acked-by, and Tested-by tags should also be amended
251 into commits in a MR before it is merged.
252
253 When providing a Reviewed-by, Acked-by, or Tested-by tag in a gitlab MR,
254 enclose the tag in backticks:
255
256 ::
257
258 `Reviewed-by: Joe Hacker <jhacker@example.com>`
259
260 This is the markdown format for literal, and will prevent gitlab from
261 hiding the < and > symbols.
262
263 Review by non-experts is encouraged. Understanding how someone else goes
264 about solving a problem is a great way to learn your way around the
265 project. The submitter is expected to evaluate whether they have an
266 appropriate amount of review feedback from people who also understand
267 the code before merging their patches.
268
269 Nominating a commit for a stable branch
270 ---------------------------------------
271
272 There are several ways to nominate a patch for inclusion in the stable
273 branch and release. In order or preference:
274
275 - By adding the ``Fixes:`` tag in the commit message as described above, if you are fixing
276 a specific commit.
277 - By adding the ``Cc: mesa-stable`` tag in the commit message as described above.
278 - By submitting a merge request against the ``staging/year.quarter``
279 branch on gitlab.
280
281 Please **DO NOT** send patches to mesa-stable@lists.freedesktop.org, it
282 is not monitored actively and is a historical artifact.
283
284 If you are not the author of the original patch, please Cc: them in your
285 nomination request.
286
287 The current patch status can be observed in the `staging
288 branch <releasing.rst#stagingbranch>`__.
289
290 .. _criteria:
291
292 Criteria for accepting patches to the stable branch
293 ---------------------------------------------------
294
295 Mesa has a designated release manager for each stable branch, and the
296 release manager is the only developer that should be pushing changes to
297 these branches. Everyone else should nominate patches using the
298 mechanism described above. The following rules define which patches are
299 accepted and which are not. The stable-release manager is also given
300 broad discretion in rejecting patches that have been nominated.
301
302 - Patch must conform with the `Basic guidelines <#guidelines>`__
303 - Patch must have landed in master first. In case where the original
304 patch is too large and/or otherwise contradicts with the rules set
305 within, a backport is appropriate.
306 - It must not introduce a regression - be that build or runtime wise.
307
308 .. note::
309 If the regression is due to faulty piglit/dEQP/CTS/other test
310 the latter must be fixed first. A reference to the offending test(s)
311 and respective fix(es) should be provided in the nominated patch.
312
313 - Patch cannot be larger than 100 lines.
314 - Patches that move code around with no functional change should be
315 rejected.
316 - Patch must be a bug fix and not a new feature.
317
318 .. note::
319 An exception to this rule, are hardware-enabling "features". For
320 example, `backports <#backports>`__ of new code to support a
321 newly-developed hardware product can be accepted if they can be
322 reasonably determined not to have effects on other hardware.
323
324 - Patch must be reviewed, For example, the commit message has
325 Reviewed-by, Signed-off-by, or Tested-by tags from someone but the
326 author.
327 - Performance patches are considered only if they provide information
328 about the hardware, program in question and observed improvement. Use
329 numbers to represent your measurements.
330
331 If the patch complies with the rules it will be
332 `cherry-picked <releasing.rst#pickntest>`__. Alternatively the release
333 manager will reply to the patch in question stating why the patch has
334 been rejected or would request a backport. The stable-release manager
335 may at times need to force-push changes to the stable branches, for
336 example, to drop a previously-picked patch that was later identified as
337 causing a regression). These force-pushes may cause changes to be lost
338 from the stable branch if developers push things directly. Consider
339 yourself warned.
340
341 .. _backports:
342
343 Sending backports for the stable branch
344 ---------------------------------------
345
346 By default merge conflicts are resolved by the stable-release manager.
347 The release maintainer should resolve trivial conflicts, but for complex
348 conflicts they should ask the original author to provide a backport or
349 de-nominate the patch.
350
351 For patches that either need to be nominated after they've landed in
352 master, or that are known ahead of time to not not apply cleanly to a
353 stable branch (such as due to a rename), using a gitlab MR is most
354 appropriate. The MR should be based on and target the
355 staging/year.quarter branch, not on the year.quarter branch, per the
356 stable branch policy. Assigning the MR to release maintainer for said
357 branch or mentioning them is helpful, but not required.
358
359 Git tips
360 --------
361
362 - ``git rebase -i ...`` is your friend. Don't be afraid to use it.
363 - Apply a fixup to commit FOO.
364
365 .. code-block:: console
366
367 git add ...
368 git commit --fixup=FOO
369 git rebase -i --autosquash ...
370
371 - Test for build breakage between patches e.g last 8 commits.
372
373 .. code-block:: console
374
375 git rebase -i --exec="ninja -C build/" HEAD~8