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| -rw-r--r-- | Documentation/SubmittingPatches | 436 |
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diff --git a/Documentation/SubmittingPatches b/Documentation/SubmittingPatches index 1671ce323a02..447671bd2927 100644 --- a/Documentation/SubmittingPatches +++ b/Documentation/SubmittingPatches @@ -10,27 +10,49 @@ kernel, the process can sometimes be daunting if you're not familiar with "the system." This text is a collection of suggestions which can greatly increase the chances of your change being accepted. -Read Documentation/SubmitChecklist for a list of items to check -before submitting code. If you are submitting a driver, also read -Documentation/SubmittingDrivers. +This document contains a large number of suggestions in a relatively terse +format. For detailed information on how the kernel development process +works, see Documentation/development-process. Also, read +Documentation/SubmitChecklist for a list of items to check before +submitting code. If you are submitting a driver, also read +Documentation/SubmittingDrivers; for device tree binding patches, read +Documentation/devicetree/bindings/submitting-patches.txt. 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. +and document a sensible set of patches. In general, use of git will make +your life as a kernel developer easier. -------------------------------------------- SECTION 1 - CREATING AND SENDING YOUR CHANGE -------------------------------------------- +0) 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, +which can be grabbed with: + + git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git + +Note, however, that you may not want to develop against the mainline tree +directly. Most subsystem maintainers run their own trees and want to see +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" ------------ -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. +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 diff(1). When creating your patch, make sure to create it @@ -42,7 +64,7 @@ not in any lower subdirectory. To create a patch for a single file, it is often sufficient to do: - SRCTREE= linux-2.6 + SRCTREE= linux MYFILE= drivers/net/mydriver.c cd $SRCTREE @@ -55,17 +77,16 @@ 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-2.6 + MYSRC= /devel/linux - tar xvfz linux-2.6.12.tar.gz - mv linux-2.6.12 linux-2.6.12-vanilla - diff -uprN -X linux-2.6.12-vanilla/Documentation/dontdiff \ - linux-2.6.12-vanilla $MYSRC > /tmp/patch + 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 diff(1)-generated -patch. The "dontdiff" file is included in the kernel tree in -2.6.12 and later. +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- @@ -83,6 +104,7 @@ is another popular alternative. 2) 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 @@ -124,10 +146,10 @@ See #3, next. When you submit or resubmit a patch or patch series, include the complete patch description and justification for it. Don't just say that this is version N of the patch (series). Don't expect the -patch merger to refer back to earlier patch versions or referenced +subsystem maintainer to refer back to earlier patch versions or referenced URLs to find the patch description and put that into the patch. I.e., the patch (series) and its description should be self-contained. -This benefits both the patch merger(s) and reviewers. Some reviewers +This benefits both the maintainers and reviewers. Some reviewers probably didn't even receive earlier versions of the patch. Describe your changes in imperative mood, e.g. "make xyzzy do frotz" @@ -156,10 +178,15 @@ Example: platform_set_drvdata(), but left the variable "dev" unused, delete it. +You should also be sure to use at least the first twelve characters of the +SHA-1 ID. The kernel repository holds a *lot* of objects, making +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 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. -Example: +SHA-1 ID, and the one line summary. For example: Fixes: e21d2170f366 ("video: remove unnecessary platform_set_drvdata()") @@ -172,8 +199,9 @@ outputting the above style in the git log or git show commands fixes = Fixes: %h (\"%s\") 3) Separate your changes. +------------------------- -Separate _logical changes_ into a single patch file. +Separate each _logical change_ into a separate patch. For example, if your changes include both bug fixes and performance enhancements for a single driver, separate those changes into two @@ -184,90 +212,116 @@ On the other hand, if you make a single change to numerous files, group those changes into a single patch. Thus a single logical change is contained within a single patch. +The point to remember is that each patch should make an easily understood +change that can be verified by reviewers. Each patch should be justifiable +on its own merits. + If one patch depends on another patch in order for a change to be complete, that is OK. Simply note "this patch depends on patch X" in your patch description. +When dividing your change into a series of patches, take special care to +ensure that the kernel builds and runs properly after each patch in the +series. Developers using "git bisect" to track down a problem can end up +splitting your patch series at any point; they will not thank you if you +introduce bugs in the middle. + If you cannot condense your patch set into a smaller set of patches, then only post say 15 or so at a time and wait for review and integration. -4) Style check your changes. +4) Style-check your changes. +---------------------------- Check your patch for basic style violations, details of which can be found in Documentation/CodingStyle. Failure to do so simply wastes the reviewers time and will get your patch rejected, probably without even being read. -At a minimum you should check your patches with the patch style -checker prior to submission (scripts/checkpatch.pl). You should -be able to justify all violations that remain in your patch. +One significant exception is when moving code from one file to +another -- in this case you should not modify the moved code at all in +the same patch which moves it. This clearly delineates the act of +moving the code and your changes. This greatly aids review of the +actual differences and allows tools to better track the history of +the code itself. + +Check your patches with the patch style checker prior to submission +(scripts/checkpatch.pl). Note, though, that the style checker should be +viewed as a guide, not as a replacement for human judgment. If your code +looks better with a violation then its probably best left alone. + +The checker reports at three levels: + - ERROR: things that are very likely to be wrong + - WARNING: things requiring careful review + - CHECK: things requiring thought +You should be able to justify all violations that remain in your +patch. -5) Select e-mail destination. +5) Select the recipients for your patch. +---------------------------------------- -Look through the MAINTAINERS file and the source code, and determine -if your change applies to a specific subsystem of the kernel, with -an assigned maintainer. If so, e-mail that person. The script -scripts/get_maintainer.pl can be very useful at this step. +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 your are working on, Andrew +Morton (akpm@linux-foundation.org) serves as a maintainer of last resort. -If no maintainer is listed, or the maintainer does not respond, send -your patch to the primary Linux kernel developer's mailing list, -linux-kernel@vger.kernel.org. Most kernel developers monitor this -e-mail list, and can comment on your changes. +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. +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. Do not send more than 15 patches at once to the vger mailing lists!!! - Linus Torvalds is the final arbiter of all changes accepted into the Linux kernel. His e-mail address is <torvalds@linux-foundation.org>. -He gets a lot of e-mail, so typically you should do your best to -avoid- +He gets a lot of e-mail, and, at this point, very few patches go through +Linus directly, so typically you should do your best to -avoid- sending him e-mail. -Patches which are bug fixes, are "obvious" changes, or similarly -require little discussion should be sent or CC'd to Linus. Patches -which require discussion or do not have a clear advantage should -usually be sent first to linux-kernel. Only after the patch is -discussed should the patch then be submitted to Linus. - - +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 distrbutors to get the patch out to users; in such cases, +obviously, the patch should not be sent to any public lists. -6) Select your CC (e-mail carbon copy) list. +Patches that fix a severe bug in a released kernel should be directed +toward the stable maintainers by putting a line like this: -Unless you have a reason NOT to do so, CC linux-kernel@vger.kernel.org. + Cc: stable@vger.kernel.org -Other kernel developers besides Linus need to be aware of your change, -so that they may comment on it and offer code review and suggestions. -linux-kernel is the primary Linux kernel developer mailing list. -Other mailing lists are available for specific subsystems, such as -USB, framebuffer devices, the VFS, the SCSI subsystem, etc. See the -MAINTAINERS file for a mailing list that relates specifically to -your change. +into your patch. -Majordomo lists of VGER.KERNEL.ORG at: - <http://vger.kernel.org/vger-lists.html> +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. -If changes affect userland-kernel interfaces, please send -the MAN-PAGES maintainer (as listed in the MAINTAINERS file) -a man-pages patch, or at least a notification of the change, -so that some information makes its way into the manual pages. - -Even if the maintainer did not respond in step #5, make sure to ALWAYS -copy the maintainer when you change their code. +If changes affect userland-kernel interfaces, please send the MAN-PAGES +maintainer (as listed in the MAINTAINERS file) a man-pages patch, or at +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 which could break grep(1) + Spelling fixes for errors which could break 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 (eg. check_region) + 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) @@ -276,7 +330,8 @@ Trivial patches must qualify for one of the following rules: -7) No MIME, no links, no compression, no attachments. Just plain text. +6) 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 @@ -299,54 +354,48 @@ you to re-send them using MIME. See Documentation/email-clients.txt for hints about configuring your e-mail client so that it sends your patches untouched. -8) E-mail size. - -When sending patches to Linus, always follow step #7. +7) E-mail size. +--------------- 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. +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. +------------------------------ +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 +bring about a comment or changelog entry so that the next reviewer better +understands what is going on. -9) Name your kernel version. +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. -It is important to note, either in the subject line or in the patch -description, the kernel version to which this patch applies. -If the patch does not apply cleanly to the latest kernel version, -Linus will not apply it. +9) 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. -10) Don't get discouraged. Re-submit. -After you have submitted your change, be patient and wait. If Linus -likes your change and applies it, it will appear in the next version -of the kernel that he releases. - -However, if your change doesn't appear in the next version of the -kernel, there could be any number of reasons. It's YOUR job to -narrow down those reasons, correct what was wrong, and submit your -updated change. - -It is quite common for Linus to "drop" your patch without comment. -That's the nature of the system. If he drops your patch, it could be -due to -* Your patch did not apply cleanly to the latest kernel version. -* Your patch was not sufficiently discussed on linux-kernel. -* A style issue (see section 2). -* An e-mail formatting issue (re-read this section). -* A technical problem with your change. -* He gets tons of e-mail, and yours got lost in the shuffle. -* You are being annoying. - -When in doubt, solicit comments on linux-kernel mailing list. - - - -11) Include PATCH in the subject +10) 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 @@ -355,7 +404,8 @@ e-mail discussions. -12) Sign your work +11) Sign your work +------------------ To improve tracking of who did what, especially with patches that can percolate to their final resting place in the kernel through several @@ -429,15 +479,15 @@ 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 2.6-stable : +here's what we see in a 3.x-stable release: - Date: Tue May 13 19:10:30 2008 +0000 +Date: Tue Oct 7 07:26:38 2014 -0400 - SCSI: libiscsi regression in 2.6.25: fix nop timer handling + libata: Un-break ATA blacklist - commit 4cf1043593db6a337f10e006c23c69e5fc93e722 upstream + commit 1c40279960bcd7d52dbdf1d466b20d24b99176c8 upstream. -And here's what appears in 2.4 : +And here's what might appear in an older kernel once a patch is backported: Date: Tue May 13 22:12:27 2008 +0200 @@ -446,18 +496,19 @@ And here's what appears in 2.4 : [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 trouble-shoot bugs in your +tracking your trees, and to people trying to troubleshoot bugs in your tree. -13) When to use Acked-by: and Cc: +12) When to use Acked-by: and Cc: +--------------------------------- 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. 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 -arrange to have an Acked-by: line added to the patch's changelog. +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 maintainer neither contributed to nor forwarded the patch. @@ -465,7 +516,8 @@ maintainer neither contributed to nor forwarded the patch. 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:. +into an Acked-by: (but note that it is usually better to ask for an +explicit ack). 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 @@ -477,11 +529,13 @@ list archives. 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. This tag documents that potentially interested parties -have been included in the discussion +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. -14) Using Reported-by:, Tested-by:, Reviewed-by:, Suggested-by: and Fixes: +13) 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 @@ -541,7 +595,13 @@ which stable kernel versions should receive your fix. This is the preferred method for indicating a bug fixed by the patch. See #2 above for more details. -15) The canonical patch format +14) 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. The canonical patch subject line is: @@ -549,7 +609,8 @@ The canonical patch subject line is: The canonical patch message body contains the following: - - A "from" line specifying the patch author. + - A "from" line specifying the patch author (only needed if the person + sending the patch is not the author). - An empty line. @@ -656,128 +717,63 @@ See more details on the proper patch format in the following references. -16) Sending "git pull" requests (from Linus emails) - -Please write the git repo address and branch name alone on the same line -so that I can't even by mistake pull from the wrong branch, and so -that a triple-click just selects the whole thing. - -So the proper format is something along the lines of: - - "Please pull from - - git://jdelvare.pck.nerim.net/jdelvare-2.6 i2c-for-linus - - to get these changes:" - -so that I don't have to hunt-and-peck for the address and inevitably -get it wrong (actually, I've only gotten it wrong a few times, and -checking against the diffstat tells me when I get it wrong, but I'm -just a lot more comfortable when I don't have to "look for" the right -thing to pull, and double-check that I have the right branch-name). - - -Please use "git diff -M --stat --summary" to generate the diffstat: -the -M enables rename detection, and the summary enables a summary of -new/deleted or renamed files. - -With rename detection, the statistics are rather different [...] -because git will notice that a fair number of the changes are renames. - ------------------------------------ -SECTION 2 - HINTS, TIPS, AND TRICKS ------------------------------------ - -This section lists many of the common "rules" associated with code -submitted to the kernel. There are always exceptions... but you must -have a really good reason for doing so. You could probably call this -section Linus Computer Science 101. - - - -1) Read Documentation/CodingStyle - -Nuff said. If your code deviates too much from this, it is likely -to be rejected without further review, and without comment. - -One significant exception is when moving code from one file to -another -- in this case you should not modify the moved code at all in -the same patch which moves it. This clearly delineates the act of -moving the code and your changes. This greatly aids review of the -actual differences and allows tools to better track the history of -the code itself. - -Check your patches with the patch style checker prior to submission -(scripts/checkpatch.pl). The style checker should be viewed as -a guide not as the final word. If your code looks better with -a violation then its probably best left alone. - -The checker reports at three levels: - - ERROR: things that are very likely to be wrong - - WARNING: things requiring careful review - - CHECK: things requiring thought - -You should be able to justify all violations that remain in your -patch. - - - -2) #ifdefs are ugly - -Code cluttered with ifdefs is difficult to read and maintain. Don't do -it. Instead, put your ifdefs in a header, and conditionally define -'static inline' functions, or macros, which are used in the code. -Let the compiler optimize away the "no-op" case. - -Simple example, of poor code: - - dev = alloc_etherdev (sizeof(struct funky_private)); - if (!dev) - return -ENODEV; - #ifdef CONFIG_NET_FUNKINESS - init_funky_net(dev); - #endif - -Cleaned-up example: - -(in header) - #ifndef CONFIG_NET_FUNKINESS - static inline void init_funky_net (struct net_device *d) {} - #endif +15) Sending "git pull" requests +------------------------------- -(in the code itself) - dev = alloc_etherdev (sizeof(struct funky_private)); - if (!dev) - return -ENODEV; - init_funky_net(dev); +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] or [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 -3) 'static inline' is better than a macro + git://jdelvare.pck.nerim.net/jdelvare-2.6 i2c-for-linus -Static inline functions are greatly preferred over macros. -They provide type safety, have no length limitations, no formatting -limitations, and under gcc they are as cheap as macros. + to get these changes:" -Macros should only be used for cases where a static inline is clearly -suboptimal [there are a few, isolated cases of this in fast paths], -or where it is impossible to use a static inline function [such as -string-izing]. +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. -'static inline' is preferred over 'static __inline__', 'extern inline', -and 'extern __inline__'. +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. -4) Don't over-design. +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. -Don't try to anticipate nebulous future cases which may or may not -be useful: "Make it as simple as you can, and no simpler." +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 ---------------------- -SECTION 3 - REFERENCES +SECTION 2 - REFERENCES ---------------------- Andrew Morton, "The perfect patch" (tpp). |