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diff --git a/Documentation/process/submitting-patches.rst b/Documentation/process/submitting-patches.rst index 1699b7f8e63a..cede4e7b29af 100644 --- a/Documentation/process/submitting-patches.rst +++ b/Documentation/process/submitting-patches.rst @@ -10,22 +10,23 @@ can greatly increase the chances of your change being accepted. This document contains a large number of suggestions in a relatively terse format. For detailed information on how the kernel development process -works, see :ref:`Documentation/process <development_process_main>`. -Also, read :ref:`Documentation/process/submit-checklist.rst <submitchecklist>` -for a list of items to check before -submitting code. If you are submitting a driver, also read -:ref:`Documentation/process/submitting-drivers.rst <submittingdrivers>`; -for device tree binding patches, read +works, see Documentation/process/development-process.rst. Also, read +Documentation/process/submit-checklist.rst +for a list of items to check before submitting code. +For device tree binding patches, read Documentation/devicetree/bindings/submitting-patches.rst. -Many of these steps describe the default behavior of the ``git`` version -control system; if you use ``git`` to prepare your patches, you'll find much -of the mechanical work done for you, though you'll still need to prepare -and document a sensible set of patches. In general, use of ``git`` will make -your life as a kernel developer easier. +This documentation assumes that you're using ``git`` to prepare your patches. +If you're unfamiliar with ``git``, you would be well-advised to learn how to +use it, it will make your life as a kernel developer and in general much +easier. -0) Obtain a current source tree -------------------------------- +Some subsystems and maintainer trees have additional information about +their workflow and expectations, see +:ref:`Documentation/process/maintainer-handbooks.rst <maintainer_handbooks_main>`. + +Obtain a current source tree +---------------------------- If you do not have a repository with the current kernel source handy, use ``git`` to obtain one. You'll want to start with the mainline repository, @@ -39,68 +40,10 @@ patches prepared against those trees. See the **T:** entry for the subsystem in the MAINTAINERS file to find that tree, or simply ask the maintainer if the tree is not listed there. -It is still possible to download kernel releases via tarballs (as described -in the next section), but that is the hard way to do kernel development. - -1) ``diff -up`` ---------------- - -If you must generate your patches by hand, use ``diff -up`` or ``diff -uprN`` -to create patches. Git generates patches in this form by default; if -you're using ``git``, you can skip this section entirely. - -All changes to the Linux kernel occur in the form of patches, as -generated by :manpage:`diff(1)`. When creating your patch, make sure to -create it in "unified diff" format, as supplied by the ``-u`` argument -to :manpage:`diff(1)`. -Also, please use the ``-p`` argument which shows which C function each -change is in - that makes the resultant ``diff`` a lot easier to read. -Patches should be based in the root kernel source directory, -not in any lower subdirectory. - -To create a patch for a single file, it is often sufficient to do:: - - SRCTREE=linux - MYFILE=drivers/net/mydriver.c - - cd $SRCTREE - cp $MYFILE $MYFILE.orig - vi $MYFILE # make your change - cd .. - diff -up $SRCTREE/$MYFILE{.orig,} > /tmp/patch - -To create a patch for multiple files, you should unpack a "vanilla", -or unmodified kernel source tree, and generate a ``diff`` against your -own source tree. For example:: - - MYSRC=/devel/linux - - tar xvfz linux-3.19.tar.gz - mv linux-3.19 linux-3.19-vanilla - diff -uprN -X linux-3.19-vanilla/Documentation/dontdiff \ - linux-3.19-vanilla $MYSRC > /tmp/patch - -``dontdiff`` is a list of files which are generated by the kernel during -the build process, and should be ignored in any :manpage:`diff(1)`-generated -patch. - -Make sure your patch does not include any extra files which do not -belong in a patch submission. Make sure to review your patch -after- -generating it with :manpage:`diff(1)`, to ensure accuracy. - -If your changes produce a lot of deltas, you need to split them into -individual patches which modify things in logical stages; see -:ref:`split_changes`. This will facilitate review by other kernel developers, -very important if you want your patch accepted. - -If you're using ``git``, ``git rebase -i`` can help you with this process. If -you're not using ``git``, ``quilt`` <http://savannah.nongnu.org/projects/quilt> -is another popular alternative. - .. _describe_changes: -2) Describe your changes ------------------------- +Describe your changes +--------------------- Describe your problem. Whether your patch is a one-line bug fix or 5000 lines of a new feature, there must be an underlying problem that @@ -133,7 +76,7 @@ as you intend it to. The maintainer will thank you if you write your patch description in a form which can be easily pulled into Linux's source code management -system, ``git``, as a "commit log". See :ref:`explicit_in_reply_to`. +system, ``git``, as a "commit log". See :ref:`the_canonical_patch_format`. Solve only one problem per patch. If your description starts to get long, that's a sign that you probably need to split up your patch. @@ -153,17 +96,6 @@ instead of "[This patch] makes xyzzy do frotz" or "[I] changed xyzzy to do frotz", as if you are giving orders to the codebase to change its behaviour. -If the patch fixes a logged bug entry, refer to that bug entry by -number and URL. If the patch follows from a mailing list discussion, -give a URL to the mailing list archive; use the https://lkml.kernel.org/ -redirector with a ``Message-Id``, to ensure that the links cannot become -stale. - -However, try to make your explanation understandable without external -resources. In addition to giving a URL to a mailing list archive or -bug, summarize the relevant points of the discussion that led to the -patch as submitted. - If you want to refer to a specific commit, don't just refer to the SHA-1 ID of the commit. Please also include the oneline summary of the commit, to make it easier for reviewers to know what it is about. @@ -180,11 +112,41 @@ collisions with shorter IDs a real possibility. Bear in mind that, even if there is no collision with your six-character ID now, that condition may change five years from now. +If related discussions or any other background information behind the change +can be found on the web, add 'Link:' tags pointing to it. If the patch is a +result of some earlier mailing list discussions or something documented on the +web, point to it. + +When linking to mailing list archives, preferably use the lore.kernel.org +message archiver service. To create the link URL, use the contents of the +``Message-ID`` header of the message without the surrounding angle brackets. +For example:: + + Link: https://lore.kernel.org/30th.anniversary.repost@klaava.Helsinki.FI + +Please check the link to make sure that it is actually working and points +to the relevant message. + +However, try to make your explanation understandable without external +resources. In addition to giving a URL to a mailing list archive or bug, +summarize the relevant points of the discussion that led to the +patch as submitted. + +In case your patch fixes a bug, use the 'Closes:' tag with a URL referencing +the report in the mailing list archives or a public bug tracker. For example:: + + Closes: https://example.com/issues/1234 + +Some bug trackers have the ability to close issues automatically when a +commit with such a tag is applied. Some bots monitoring mailing lists can +also track such tags and take certain actions. Private bug trackers and +invalid URLs are forbidden. + If your patch fixes a bug in a specific commit, e.g. you found an issue using -``git bisect``, please use the 'Fixes:' tag with the first 12 characters of -the SHA-1 ID, and the one line summary. Do not split the tag across multiple -lines, tags are exempt from the "wrap at 75 columns" rule in order to simplify -parsing scripts. For example:: +``git bisect``, please use the 'Fixes:' tag with at least the first 12 +characters of the SHA-1 ID, and the one line summary. Do not split the tag +across multiple lines, tags are exempt from the "wrap at 75 columns" rule in +order to simplify parsing scripts. For example:: Fixes: 54a4f0239f2e ("KVM: MMU: make kvm_mmu_zap_page() return the number of pages it actually freed") @@ -196,10 +158,15 @@ outputting the above style in the ``git log`` or ``git show`` commands:: [pretty] fixes = Fixes: %h (\"%s\") +An example call:: + + $ git log -1 --pretty=fixes 54a4f0239f2e + Fixes: 54a4f0239f2e ("KVM: MMU: make kvm_mmu_zap_page() return the number of pages it actually freed") + .. _split_changes: -3) Separate your changes ------------------------- +Separate your changes +--------------------- Separate each **logical change** into a separate patch. @@ -231,12 +198,11 @@ then only post say 15 or so at a time and wait for review and integration. -4) Style-check your changes ---------------------------- +Style-check your changes +------------------------ Check your patch for basic style violations, details of which can be -found in -:ref:`Documentation/process/coding-style.rst <codingstyle>`. +found in Documentation/process/coding-style.rst. Failure to do so simply wastes the reviewers time and will get your patch rejected, probably without even being read. @@ -262,28 +228,24 @@ You should be able to justify all violations that remain in your patch. -5) Select the recipients for your patch ---------------------------------------- - -You should always copy the appropriate subsystem maintainer(s) on any patch -to code that they maintain; look through the MAINTAINERS file and the -source code revision history to see who those maintainers are. The -script scripts/get_maintainer.pl can be very useful at this step. If you -cannot find a maintainer for the subsystem you are working on, Andrew -Morton (akpm@linux-foundation.org) serves as a maintainer of last resort. +Select the recipients for your patch +------------------------------------ -You should also normally choose at least one mailing list to receive a copy -of your patch set. linux-kernel@vger.kernel.org functions as a list of -last resort, but the volume on that list has caused a number of developers -to tune it out. Look in the MAINTAINERS file for a subsystem-specific -list; your patch will probably get more attention there. Please do not -spam unrelated lists, though. +You should always copy the appropriate subsystem maintainer(s) and list(s) on +any patch to code that they maintain; look through the MAINTAINERS file and the +source code revision history to see who those maintainers are. The script +scripts/get_maintainer.pl can be very useful at this step (pass paths to your +patches as arguments to scripts/get_maintainer.pl). If you cannot find a +maintainer for the subsystem you are working on, Andrew Morton +(akpm@linux-foundation.org) serves as a maintainer of last resort. -Many kernel-related lists are hosted on vger.kernel.org; you can find a -list of them at http://vger.kernel.org/vger-lists.html. There are -kernel-related lists hosted elsewhere as well, though. +linux-kernel@vger.kernel.org should be used by default for all patches, but the +volume on that list has caused a number of developers to tune it out. Please +do not spam unrelated lists and unrelated people, though. -Do not send more than 15 patches at once to the vger mailing lists!!! +Many kernel-related lists are hosted at kernel.org; you can find a list +of them at https://subspace.kernel.org. There are kernel-related lists +hosted elsewhere as well, though. Linus Torvalds is the final arbiter of all changes accepted into the Linux kernel. His e-mail address is <torvalds@linux-foundation.org>. @@ -294,7 +256,8 @@ sending him e-mail. If you have a patch that fixes an exploitable security bug, send that patch to security@kernel.org. For severe bugs, a short embargo may be considered to allow distributors to get the patch out to users; in such cases, -obviously, the patch should not be sent to any public lists. +obviously, the patch should not be sent to any public lists. See also +Documentation/process/security-bugs.rst. Patches that fix a severe bug in a released kernel should be directed toward the stable maintainers by putting a line like this:: @@ -302,14 +265,8 @@ toward the stable maintainers by putting a line like this:: Cc: stable@vger.kernel.org into the sign-off area of your patch (note, NOT an email recipient). You -should also read -:ref:`Documentation/process/stable-kernel-rules.rst <stable_kernel_rules>` -in addition to this file. - -Note, however, that some subsystem maintainers want to come to their own -conclusions on which patches should go to the stable trees. The networking -maintainer, in particular, would rather not see individual developers -adding lines like the above to their patches. +should also read Documentation/process/stable-kernel-rules.rst +in addition to this document. If changes affect userland-kernel interfaces, please send the MAN-PAGES maintainer (as listed in the MAINTAINERS file) a man-pages patch, or at @@ -317,35 +274,21 @@ least a notification of the change, so that some information makes its way into the manual pages. User-space API changes should also be copied to linux-api@vger.kernel.org. -For small patches you may want to CC the Trivial Patch Monkey -trivial@kernel.org which collects "trivial" patches. Have a look -into the MAINTAINERS file for its current manager. -Trivial patches must qualify for one of the following rules: - -- Spelling fixes in documentation -- Spelling fixes for errors which could break :manpage:`grep(1)` -- Warning fixes (cluttering with useless warnings is bad) -- Compilation fixes (only if they are actually correct) -- Runtime fixes (only if they actually fix things) -- Removing use of deprecated functions/macros -- Contact detail and documentation fixes -- Non-portable code replaced by portable code (even in arch-specific, - since people copy, as long as it's trivial) -- Any fix by the author/maintainer of the file (ie. patch monkey - in re-transmission mode) - - - -6) No MIME, no links, no compression, no attachments. Just plain text ----------------------------------------------------------------------- +No MIME, no links, no compression, no attachments. Just plain text +------------------------------------------------------------------- Linus and other kernel developers need to be able to read and comment on the changes you are submitting. It is important for a kernel developer to be able to "quote" your changes, using standard e-mail tools, so that they may comment on specific portions of your code. -For this reason, all patches should be submitted by e-mail "inline". +For this reason, all patches should be submitted by e-mail "inline". The +easiest way to do this is with ``git send-email``, which is strongly +recommended. An interactive tutorial for ``git send-email`` is available at +https://git-send-email.io. + +If you choose not to use ``git send-email``: .. warning:: @@ -361,62 +304,97 @@ decreasing the likelihood of your MIME-attached change being accepted. Exception: If your mailer is mangling patches then someone may ask you to re-send them using MIME. -See :ref:`Documentation/process/email-clients.rst <email_clients>` -for hints about configuring your e-mail client so that it sends your patches -untouched. - -7) E-mail size --------------- +See Documentation/process/email-clients.rst for hints about configuring +your e-mail client so that it sends your patches untouched. -Large changes are not appropriate for mailing lists, and some -maintainers. If your patch, uncompressed, exceeds 300 kB in size, -it is preferred that you store your patch on an Internet-accessible -server, and provide instead a URL (link) pointing to your patch. But note -that if your patch exceeds 300 kB, it almost certainly needs to be broken up -anyway. - -8) Respond to review comments ------------------------------ +Respond to review comments +-------------------------- Your patch will almost certainly get comments from reviewers on ways in -which the patch can be improved. You must respond to those comments; -ignoring reviewers is a good way to get ignored in return. Review comments -or questions that do not lead to a code change should almost certainly +which the patch can be improved, in the form of a reply to your email. You must +respond to those comments; ignoring reviewers is a good way to get ignored in +return. You can simply reply to their emails to answer their comments. Review +comments or questions that do not lead to a code change should almost certainly bring about a comment or changelog entry so that the next reviewer better understands what is going on. Be sure to tell the reviewers what changes you are making and to thank them for their time. Code review is a tiring and time-consuming process, and reviewers sometimes get grumpy. Even in that case, though, respond -politely and address the problems they have pointed out. +politely and address the problems they have pointed out. When sending a next +version, add a ``patch changelog`` to the cover letter or to individual patches +explaining difference against previous submission (see +:ref:`the_canonical_patch_format`). +Notify people that commented on your patch about new versions by adding them to +the patches CC list. + +See Documentation/process/email-clients.rst for recommendations on email +clients and mailing list etiquette. + +.. _interleaved_replies: + +Use trimmed interleaved replies in email discussions +---------------------------------------------------- +Top-posting is strongly discouraged in Linux kernel development +discussions. Interleaved (or "inline") replies make conversations much +easier to follow. For more details see: +https://en.wikipedia.org/wiki/Posting_style#Interleaved_style + +As is frequently quoted on the mailing list:: + A: http://en.wikipedia.org/wiki/Top_post + Q: Were do I find info about this thing called top-posting? + A: Because it messes up the order in which people normally read text. + Q: Why is top-posting such a bad thing? + A: Top-posting. + Q: What is the most annoying thing in e-mail? -9) Don't get discouraged - or impatient ---------------------------------------- +Similarly, please trim all unneeded quotations that aren't relevant +to your reply. This makes responses easier to find, and saves time and +space. For more details see: http://daringfireball.net/2007/07/on_top :: + + A: No. + Q: Should I include quotations after my reply? + +.. _resend_reminders: + +Don't get discouraged - or impatient +------------------------------------ After you have submitted your change, be patient and wait. Reviewers are busy people and may not get to your patch right away. Once upon a time, patches used to disappear into the void without comment, but the development process works more smoothly than that now. You should -receive comments within a week or so; if that does not happen, make sure -that you have sent your patches to the right place. Wait for a minimum of -one week before resubmitting or pinging reviewers - possibly longer during -busy times like merge windows. +receive comments within a few weeks (typically 2-3); if that does not +happen, make sure that you have sent your patches to the right place. +Wait for a minimum of one week before resubmitting or pinging reviewers +- possibly longer during busy times like merge windows. + +It's also ok to resend the patch or the patch series after a couple of +weeks with the word "RESEND" added to the subject line:: + [PATCH Vx RESEND] sub/sys: Condensed patch summary -10) Include PATCH in the subject --------------------------------- +Don't add "RESEND" when you are submitting a modified version of your +patch or patch series - "RESEND" only applies to resubmission of a +patch or patch series which have not been modified in any way from the +previous submission. + + +Include PATCH in the subject +----------------------------- Due to high e-mail traffic to Linus, and to linux-kernel, it is common convention to prefix your subject line with [PATCH]. This lets Linus and other kernel developers more easily distinguish patches from other e-mail discussions. +``git send-email`` will do this for you automatically. -11) Sign your work - the Developer's Certificate of Origin ----------------------------------------------------------- +Sign your work - the Developer's Certificate of Origin +------------------------------------------------------ To improve tracking of who did what, especially with patches that can percolate to their final resting place in the kernel through several @@ -459,61 +437,24 @@ then you just add a line saying:: Signed-off-by: Random J Developer <random@developer.example.org> -using your real name (sorry, no pseudonyms or anonymous contributions.) +using a known identity (sorry, no anonymous contributions.) +This will be done for you automatically if you use ``git commit -s``. +Reverts should also include "Signed-off-by". ``git revert -s`` does that +for you. Some people also put extra tags at the end. They'll just be ignored for now, but you can do this to mark internal company procedures or just point out some special detail about the sign-off. -If you are a subsystem or branch maintainer, sometimes you need to slightly -modify patches you receive in order to merge them, because the code is not -exactly the same in your tree and the submitters'. If you stick strictly to -rule (c), you should ask the submitter to rediff, but this is a totally -counter-productive waste of time and energy. Rule (b) allows you to adjust -the code, but then it is very impolite to change one submitter's code and -make him endorse your bugs. To solve this problem, it is recommended that -you add a line between the last Signed-off-by header and yours, indicating -the nature of your changes. While there is nothing mandatory about this, it -seems like prepending the description with your mail and/or name, all -enclosed in square brackets, is noticeable enough to make it obvious that -you are responsible for last-minute changes. Example:: - - Signed-off-by: Random J Developer <random@developer.example.org> - [lucky@maintainer.example.org: struct foo moved from foo.c to foo.h] - Signed-off-by: Lucky K Maintainer <lucky@maintainer.example.org> - -This practice is particularly helpful if you maintain a stable branch and -want at the same time to credit the author, track changes, merge the fix, -and protect the submitter from complaints. Note that under no circumstances -can you change the author's identity (the From header), as it is the one -which appears in the changelog. - -Special note to back-porters: It seems to be a common and useful practice -to insert an indication of the origin of a patch at the top of the commit -message (just after the subject line) to facilitate tracking. For instance, -here's what we see in a 3.x-stable release:: - - Date: Tue Oct 7 07:26:38 2014 -0400 - - libata: Un-break ATA blacklist +Any further SoBs (Signed-off-by:'s) following the author's SoB are from +people handling and transporting the patch, but were not involved in its +development. SoB chains should reflect the **real** route a patch took +as it was propagated to the maintainers and ultimately to Linus, with +the first SoB entry signalling primary authorship of a single author. - commit 1c40279960bcd7d52dbdf1d466b20d24b99176c8 upstream. -And here's what might appear in an older kernel once a patch is backported:: - - Date: Tue May 13 22:12:27 2008 +0200 - - wireless, airo: waitbusy() won't delay - - [backport of 2.6 commit b7acbdfbd1f277c1eb23f344f899cfa4cd0bf36a] - -Whatever the format, this information provides a valuable help to people -tracking your trees, and to people trying to troubleshoot bugs in your -tree. - - -12) When to use Acked-by:, Cc:, and Co-developed-by: -------------------------------------------------------- +When to use Acked-by:, Cc:, and Co-developed-by: +------------------------------------------------ The Signed-off-by: tag indicates that the signer was involved in the development of the patch, or that he/she was in the patch's delivery path. @@ -522,31 +463,45 @@ If a person was not directly involved in the preparation or handling of a patch but wishes to signify and record their approval of it then they can ask to have an Acked-by: line added to the patch's changelog. -Acked-by: is often used by the maintainer of the affected code when that +Acked-by: is meant to be used by those responsible for or involved with the +affected code in one way or another. Most commonly, the maintainer when that maintainer neither contributed to nor forwarded the patch. +Acked-by: may also be used by other stakeholders, such as people with domain +knowledge (e.g. the original author of the code being modified), userspace-side +reviewers for a kernel uAPI patch or key users of a feature. Optionally, in +these cases, it can be useful to add a "# Suffix" to clarify its meaning:: + + Acked-by: The Stakeholder <stakeholder@example.org> # As primary user + Acked-by: is not as formal as Signed-off-by:. It is a record that the acker has at least reviewed the patch and has indicated acceptance. Hence patch mergers will sometimes manually convert an acker's "yep, looks good to me" into an Acked-by: (but note that it is usually better to ask for an explicit ack). +Acked-by: is also less formal than Reviewed-by:. For instance, maintainers may +use it to signify that they are OK with a patch landing, but they may not have +reviewed it as thoroughly as if a Reviewed-by: was provided. Similarly, a key +user may not have carried out a technical review of the patch, yet they may be +satisfied with the general approach, the feature or the user-facing interface. + Acked-by: does not necessarily indicate acknowledgement of the entire patch. For example, if a patch affects multiple subsystems and has an Acked-by: from one subsystem maintainer then this usually indicates acknowledgement of just the part which affects that maintainer's code. Judgement should be used here. When in doubt people should refer to the original discussion in the mailing -list archives. +list archives. A "# Suffix" may also be used in this case to clarify. If a person has had the opportunity to comment on a patch, but has not provided such comments, you may optionally add a ``Cc:`` tag to the patch. -This is the only tag which might be added without an explicit action by the -person it names - but it should indicate that this person was copied on the -patch. This tag documents that potentially interested parties -have been included in the discussion. +This tag documents that potentially interested parties have been included in +the discussion. Note, this is one of only three tags you might be able to use +without explicit permission of the person named (see 'Tagging people requires +permission' below for details). Co-developed-by: states that the patch was co-created by multiple developers; -it is a used to give attribution to co-authors (in addition to the author +it is used to give attribution to co-authors (in addition to the author attributed by the From: tag) when several people work on a single patch. Since Co-developed-by: denotes authorship, every Co-developed-by: must be immediately followed by a Signed-off-by: of the associated co-author. Standard sign-off @@ -581,13 +536,17 @@ Example of a patch submitted by a Co-developed-by: author:: Signed-off-by: Submitting Co-Author <sub@coauthor.example.org> -13) Using Reported-by:, Tested-by:, Reviewed-by:, Suggested-by: and Fixes: --------------------------------------------------------------------------- +Using Reported-by:, Tested-by:, Reviewed-by:, Suggested-by: and Fixes: +---------------------------------------------------------------------- The Reported-by tag gives credit to people who find bugs and report them and it -hopefully inspires them to help us again in the future. Please note that if -the bug was reported in private, then ask for permission first before using the -Reported-by tag. +hopefully inspires them to help us again in the future. The tag is intended for +bugs; please do not use it to credit feature requests. The tag should be +followed by a Closes: tag pointing to the report, unless the report is not +available on the web. The Link: tag can be used instead of Closes: if the patch +fixes a part of the issue(s) being reported. Note, the Reported-by tag is one +of only three tags you might be able to use without explicit permission of the +person named (see 'Tagging people requires permission' below for details). A Tested-by: tag indicates that the patch has been successfully tested (in some environment) by the person named. This tag informs maintainers that @@ -629,12 +588,19 @@ done on the patch. Reviewed-by: tags, when supplied by reviewers known to understand the subject area and to perform thorough reviews, will normally increase the likelihood of your patch getting into the kernel. +Both Tested-by and Reviewed-by tags, once received on mailing list from tester +or reviewer, should be added by author to the applicable patches when sending +next versions. However if the patch has changed substantially in following +version, these tags might not be applicable anymore and thus should be removed. +Usually removal of someone's Tested-by or Reviewed-by tags should be mentioned +in the patch changelog (after the '---' separator). + A Suggested-by: tag indicates that the patch idea is suggested by the person -named and ensures credit to the person for the idea. Please note that this -tag should not be added without the reporter's permission, especially if the -idea was not posted in a public forum. That said, if we diligently credit our -idea reporters, they will, hopefully, be inspired to help us again in the -future. +named and ensures credit to the person for the idea: if we diligently credit +our idea reporters, they will, hopefully, be inspired to help us again in the +future. Note, this is one of only three tags you might be able to use without +explicit permission of the person named (see 'Tagging people requires +permission' below for details). A Fixes: tag indicates that the patch fixes an issue in a previous commit. It is used to make it easy to determine where a bug originated, which can help @@ -643,16 +609,43 @@ which stable kernel versions should receive your fix. This is the preferred method for indicating a bug fixed by the patch. See :ref:`describe_changes` for more details. +Note: Attaching a Fixes: tag does not subvert the stable kernel rules +process nor the requirement to Cc: stable@vger.kernel.org on all stable +patch candidates. For more information, please read +Documentation/process/stable-kernel-rules.rst. + +Finally, while providing tags is welcome and typically very appreciated, please +note that signers (i.e. submitters and maintainers) may use their discretion in +applying offered tags. + +.. _tagging_people: + +Tagging people requires permission +---------------------------------- + +Be careful in the addition of the aforementioned tags to your patches, as all +except for Cc:, Reported-by:, and Suggested-by: need explicit permission of the +person named. For those three implicit permission is sufficient if the person +contributed to the Linux kernel using that name and email address according +to the lore archives or the commit history -- and in case of Reported-by: +and Suggested-by: did the reporting or suggestion in public. Note, +bugzilla.kernel.org is a public place in this sense, but email addresses +used there are private; so do not expose them in tags, unless the person +used them in earlier contributions. + .. _the_canonical_patch_format: -14) The canonical patch format ------------------------------- +The canonical patch format +-------------------------- This section describes how the patch itself should be formatted. Note that, if you have your patches stored in a ``git`` repository, proper patch formatting can be had with ``git format-patch``. The tools cannot create the necessary text, though, so read the instructions below anyway. +Subject Line +^^^^^^^^^^^^ + The canonical patch subject line is:: Subject: [PATCH 001/123] subsystem: summary phrase @@ -712,16 +705,22 @@ not considered part of the summary phrase, but describe how the patch should be treated. Common tags might include a version descriptor if the multiple versions of the patch have been sent out in response to comments (i.e., "v1, v2, v3"), or "RFC" to indicate a request for -comments. If there are four patches in a patch series the individual -patches may be numbered like this: 1/4, 2/4, 3/4, 4/4. This assures -that developers understand the order in which the patches should be -applied and that they have reviewed or applied all of the patches in -the patch series. +comments. -A couple of example Subjects:: +If there are four patches in a patch series the individual patches may +be numbered like this: 1/4, 2/4, 3/4, 4/4. This assures that developers +understand the order in which the patches should be applied and that +they have reviewed or applied all of the patches in the patch series. + +Here are some good example Subjects:: Subject: [PATCH 2/5] ext2: improve scalability of bitmap searching Subject: [PATCH v2 01/27] x86: fix eflags tracking + Subject: [PATCH v2] sub/sys: Condensed patch summary + Subject: [PATCH v2 M/N] sub/sys: Condensed patch summary + +From Line +^^^^^^^^^ The ``from`` line must be the very first line in the message body, and has the form: @@ -733,43 +732,97 @@ patch in the permanent changelog. If the ``from`` line is missing, then the ``From:`` line from the email header will be used to determine the patch author in the changelog. -The explanation body will be committed to the permanent source -changelog, so should make sense to a competent reader who has long -since forgotten the immediate details of the discussion that might -have led to this patch. Including symptoms of the failure which the -patch addresses (kernel log messages, oops messages, etc.) is -especially useful for people who might be searching the commit logs -looking for the applicable patch. If a patch fixes a compile failure, -it may not be necessary to include _all_ of the compile failures; just -enough that it is likely that someone searching for the patch can find -it. As in the ``summary phrase``, it is important to be both succinct as -well as descriptive. - -The ``---`` marker line serves the essential purpose of marking for patch -handling tools where the changelog message ends. - -One good use for the additional comments after the ``---`` marker is for -a ``diffstat``, to show what files have changed, and the number of -inserted and deleted lines per file. A ``diffstat`` is especially useful -on bigger patches. Other comments relevant only to the moment or the -maintainer, not suitable for the permanent changelog, should also go -here. A good example of such comments might be ``patch changelogs`` -which describe what has changed between the v1 and v2 version of the -patch. +The author may indicate their affiliation or the sponsor of the work +by adding the name of an organization to the ``from`` and ``SoB`` lines, +e.g.: + + From: Patch Author (Company) <author@example.com> + +Explanation Body +^^^^^^^^^^^^^^^^ -If you are going to include a ``diffstat`` after the ``---`` marker, please -use ``diffstat`` options ``-p 1 -w 70`` so that filenames are listed from -the top of the kernel source tree and don't use too much horizontal -space (easily fit in 80 columns, maybe with some indentation). (``git`` -generates appropriate diffstats by default.) +The explanation body will be committed to the permanent source +changelog, so should make sense to a competent reader who has long since +forgotten the immediate details of the discussion that might have led to +this patch. Including symptoms of the failure which the patch addresses +(kernel log messages, oops messages, etc.) are especially useful for +people who might be searching the commit logs looking for the applicable +patch. The text should be written in such detail so that when read +weeks, months or even years later, it can give the reader the needed +details to grasp the reasoning for **why** the patch was created. + +If a patch fixes a compile failure, it may not be necessary to include +_all_ of the compile failures; just enough that it is likely that +someone searching for the patch can find it. As in the ``summary +phrase``, it is important to be both succinct as well as descriptive. + +.. _backtraces: + +Backtraces in commit messages +""""""""""""""""""""""""""""" + +Backtraces help document the call chain leading to a problem. However, +not all backtraces are helpful. For example, early boot call chains are +unique and obvious. Copying the full dmesg output verbatim, however, +adds distracting information like timestamps, module lists, register and +stack dumps. + +Therefore, the most useful backtraces should distill the relevant +information from the dump, which makes it easier to focus on the real +issue. Here is an example of a well-trimmed backtrace:: + + unchecked MSR access error: WRMSR to 0xd51 (tried to write 0x0000000000000064) + at rIP: 0xffffffffae059994 (native_write_msr+0x4/0x20) + Call Trace: + mba_wrmsr + update_domains + rdtgroup_mkdir + +Commentary +^^^^^^^^^^ + +The ``---`` marker line serves the essential purpose of marking for +patch handling tools where the changelog message ends. + +One good use for the additional comments after the ``---`` marker is +for a ``diffstat``, to show what files have changed, and the number of +inserted and deleted lines per file. A ``diffstat`` is especially useful +on bigger patches. If you are going to include a ``diffstat`` after the +``---`` marker, please use ``diffstat`` options ``-p 1 -w 70`` so that +filenames are listed from the top of the kernel source tree and don't +use too much horizontal space (easily fit in 80 columns, maybe with some +indentation). (``git`` generates appropriate diffstats by default.) + +Other comments relevant only to the moment or the maintainer, not +suitable for the permanent changelog, should also go here. A good +example of such comments might be ``patch changelogs`` which describe +what has changed between the v1 and v2 version of the patch. + +Please put this information **after** the ``---`` line which separates +the changelog from the rest of the patch. The version information is +not part of the changelog which gets committed to the git tree. It is +additional information for the reviewers. If it's placed above the +commit tags, it needs manual interaction to remove it. If it is below +the separator line, it gets automatically stripped off when applying the +patch:: + + <commit message> + ... + Signed-off-by: Author <author@mail> + --- + V2 -> V3: Removed redundant helper function + V1 -> V2: Cleaned up coding style and addressed review comments + + path/to/file | 5+++-- + ... See more details on the proper patch format in the following references. .. _explicit_in_reply_to: -15) Explicit In-Reply-To headers --------------------------------- +Explicit In-Reply-To headers +---------------------------- It can be helpful to manually add In-Reply-To: headers to a patch (e.g., when using ``git send-email``) to associate the patch with @@ -778,18 +831,22 @@ the bug report. However, for a multi-patch series, it is generally best to avoid using In-Reply-To: to link to older versions of the series. This way multiple versions of the patch don't become an unmanageable forest of references in email clients. If a link is -helpful, you can use the https://lkml.kernel.org/ redirector (e.g., in +helpful, you can use the https://lore.kernel.org/ redirector (e.g., in the cover email text) to link to an earlier version of the patch series. -16) Providing base tree information ------------------------------------ +Providing base tree information +------------------------------- When other developers receive your patches and start the review process, -it is often useful for them to know where in the tree history they -should place your work. This is particularly useful for automated CI -processes that attempt to run a series of tests in order to establish -the quality of your submission before the maintainer starts the review. +it is absolutely necessary for them to know what is the base +commit/branch your work applies on, considering the sheer amount of +maintainer trees present nowadays. Note again the **T:** entry in the +MAINTAINERS file explained above. + +This is even more important for automated CI processes that attempt to +run a series of tests in order to establish the quality of your +submission before the maintainer starts the review. If you are using ``git format-patch`` to generate your patches, you can automatically include the base tree information in your submission by @@ -832,67 +889,23 @@ letter or in the first patch of the series and it should be placed either below the ``---`` line or at the very bottom of all other content, right before your email signature. +Make sure that base commit is in an official maintainer/mainline tree +and not in some internal, accessible only to you tree - otherwise it +would be worthless. -17) Sending ``git pull`` requests ---------------------------------- - -If you have a series of patches, it may be most convenient to have the -maintainer pull them directly into the subsystem repository with a -``git pull`` operation. Note, however, that pulling patches from a developer -requires a higher degree of trust than taking patches from a mailing list. -As a result, many subsystem maintainers are reluctant to take pull -requests, especially from new, unknown developers. If in doubt you can use -the pull request as the cover letter for a normal posting of the patch -series, giving the maintainer the option of using either. - -A pull request should have [GIT PULL] in the subject line. The -request itself should include the repository name and the branch of -interest on a single line; it should look something like:: - - Please pull from - - git://jdelvare.pck.nerim.net/jdelvare-2.6 i2c-for-linus - - to get these changes: - -A pull request should also include an overall message saying what will be -included in the request, a ``git shortlog`` listing of the patches -themselves, and a ``diffstat`` showing the overall effect of the patch series. -The easiest way to get all this information together is, of course, to let -``git`` do it for you with the ``git request-pull`` command. - -Some maintainers (including Linus) want to see pull requests from signed -commits; that increases their confidence that the request actually came -from you. Linus, in particular, will not pull from public hosting sites -like GitHub in the absence of a signed tag. - -The first step toward creating such tags is to make a GNUPG key and get it -signed by one or more core kernel developers. This step can be hard for -new developers, but there is no way around it. Attending conferences can -be a good way to find developers who can sign your key. - -Once you have prepared a patch series in ``git`` that you wish to have somebody -pull, create a signed tag with ``git tag -s``. This will create a new tag -identifying the last commit in the series and containing a signature -created with your private key. You will also have the opportunity to add a -changelog-style message to the tag; this is an ideal place to describe the -effects of the pull request as a whole. - -If the tree the maintainer will be pulling from is not the repository you -are working from, don't forget to push the signed tag explicitly to the -public tree. - -When generating your pull request, use the signed tag as the target. A -command like this will do the trick:: - - git request-pull master git://my.public.tree/linux.git my-signed-tag +Tooling +------- +Many of the technical aspects of this process can be automated using +b4, documented at <https://b4.docs.kernel.org/en/latest/>. This can +help with things like tracking dependencies, running checkpatch and +with formatting and sending mails. References ---------- Andrew Morton, "The perfect patch" (tpp). - <http://www.ozlabs.org/~akpm/stuff/tpp.txt> + <https://www.ozlabs.org/~akpm/stuff/tpp.txt> Jeff Garzik, "Linux kernel patch submission format". <https://web.archive.org/web/20180829112450/http://linux.yyz.us/patch-format.html> @@ -910,14 +923,10 @@ Greg Kroah-Hartman, "How to piss off a kernel subsystem maintainer". <http://www.kroah.com/log/linux/maintainer-06.html> -NO!!!! No more huge patch bombs to linux-kernel@vger.kernel.org people! - <https://lkml.org/lkml/2005/7/11/336> - -Kernel Documentation/process/coding-style.rst: - :ref:`Documentation/process/coding-style.rst <codingstyle>` +Kernel Documentation/process/coding-style.rst Linus Torvalds's mail on the canonical patch format: - <http://lkml.org/lkml/2005/4/7/183> + <https://lore.kernel.org/r/Pine.LNX.4.58.0504071023190.28951@ppc970.osdl.org> Andi Kleen, "On submitting kernel patches" Some strategies to get difficult or controversial changes in. |