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f56d35e7aa
Fix a typo in SubmittingPatches where "probably" was spelt "probabally". Signed-off-by: Linus Nilsson <lajnold@gmail.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
568 lines
20 KiB
Plaintext
568 lines
20 KiB
Plaintext
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How to Get Your Change Into the Linux Kernel
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or
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Care And Operation Of Your Linus Torvalds
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For a person or company who wishes to submit a change to the Linux
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kernel, the process can sometimes be daunting if you're not familiar
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with "the system." This text is a collection of suggestions which
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can greatly increase the chances of your change being accepted.
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Read Documentation/SubmitChecklist for a list of items to check
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before submitting code. If you are submitting a driver, also read
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Documentation/SubmittingDrivers.
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--------------------------------------------
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SECTION 1 - CREATING AND SENDING YOUR CHANGE
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--------------------------------------------
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1) "diff -up"
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------------
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Use "diff -up" or "diff -uprN" to create patches.
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All changes to the Linux kernel occur in the form of patches, as
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generated by diff(1). When creating your patch, make sure to create it
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in "unified diff" format, as supplied by the '-u' argument to diff(1).
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Also, please use the '-p' argument which shows which C function each
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change is in - that makes the resultant diff a lot easier to read.
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Patches should be based in the root kernel source directory,
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not in any lower subdirectory.
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To create a patch for a single file, it is often sufficient to do:
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SRCTREE= linux-2.6
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MYFILE= drivers/net/mydriver.c
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cd $SRCTREE
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cp $MYFILE $MYFILE.orig
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vi $MYFILE # make your change
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cd ..
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diff -up $SRCTREE/$MYFILE{.orig,} > /tmp/patch
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To create a patch for multiple files, you should unpack a "vanilla",
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or unmodified kernel source tree, and generate a diff against your
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own source tree. For example:
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MYSRC= /devel/linux-2.6
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tar xvfz linux-2.6.12.tar.gz
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mv linux-2.6.12 linux-2.6.12-vanilla
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diff -uprN -X linux-2.6.12-vanilla/Documentation/dontdiff \
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linux-2.6.12-vanilla $MYSRC > /tmp/patch
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"dontdiff" is a list of files which are generated by the kernel during
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the build process, and should be ignored in any diff(1)-generated
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patch. The "dontdiff" file is included in the kernel tree in
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2.6.12 and later. For earlier kernel versions, you can get it
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from <http://www.xenotime.net/linux/doc/dontdiff>.
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Make sure your patch does not include any extra files which do not
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belong in a patch submission. Make sure to review your patch -after-
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generated it with diff(1), to ensure accuracy.
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If your changes produce a lot of deltas, you may want to look into
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splitting them into individual patches which modify things in
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logical stages. This will facilitate easier reviewing by other
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kernel developers, very important if you want your patch accepted.
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There are a number of scripts which can aid in this:
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Quilt:
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http://savannah.nongnu.org/projects/quilt
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Andrew Morton's patch scripts:
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http://www.zip.com.au/~akpm/linux/patches/
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Instead of these scripts, quilt is the recommended patch management
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tool (see above).
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2) Describe your changes.
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Describe the technical detail of the change(s) your patch includes.
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Be as specific as possible. The WORST descriptions possible include
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things like "update driver X", "bug fix for driver X", or "this patch
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includes updates for subsystem X. Please apply."
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If your description starts to get long, that's a sign that you probably
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need to split up your patch. See #3, next.
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3) Separate your changes.
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Separate _logical changes_ into a single patch file.
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For example, if your changes include both bug fixes and performance
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enhancements for a single driver, separate those changes into two
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or more patches. If your changes include an API update, and a new
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driver which uses that new API, separate those into two patches.
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On the other hand, if you make a single change to numerous files,
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group those changes into a single patch. Thus a single logical change
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is contained within a single patch.
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If one patch depends on another patch in order for a change to be
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complete, that is OK. Simply note "this patch depends on patch X"
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in your patch description.
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If you cannot condense your patch set into a smaller set of patches,
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then only post say 15 or so at a time and wait for review and integration.
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4) Style check your changes.
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Check your patch for basic style violations, details of which can be
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found in Documentation/CodingStyle. Failure to do so simply wastes
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the reviewers time and will get your patch rejected, probably
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without even being read.
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At a minimum you should check your patches with the patch style
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checker prior to submission (scripts/patchcheck.pl). You should
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be able to justify all violations that remain in your patch.
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5) Select e-mail destination.
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Look through the MAINTAINERS file and the source code, and determine
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if your change applies to a specific subsystem of the kernel, with
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an assigned maintainer. If so, e-mail that person.
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If no maintainer is listed, or the maintainer does not respond, send
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your patch to the primary Linux kernel developer's mailing list,
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linux-kernel@vger.kernel.org. Most kernel developers monitor this
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e-mail list, and can comment on your changes.
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Do not send more than 15 patches at once to the vger mailing lists!!!
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Linus Torvalds is the final arbiter of all changes accepted into the
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Linux kernel. His e-mail address is <torvalds@linux-foundation.org>.
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He gets a lot of e-mail, so typically you should do your best to -avoid-
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sending him e-mail.
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Patches which are bug fixes, are "obvious" changes, or similarly
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require little discussion should be sent or CC'd to Linus. Patches
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which require discussion or do not have a clear advantage should
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usually be sent first to linux-kernel. Only after the patch is
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discussed should the patch then be submitted to Linus.
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6) Select your CC (e-mail carbon copy) list.
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Unless you have a reason NOT to do so, CC linux-kernel@vger.kernel.org.
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Other kernel developers besides Linus need to be aware of your change,
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so that they may comment on it and offer code review and suggestions.
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linux-kernel is the primary Linux kernel developer mailing list.
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Other mailing lists are available for specific subsystems, such as
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USB, framebuffer devices, the VFS, the SCSI subsystem, etc. See the
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MAINTAINERS file for a mailing list that relates specifically to
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your change.
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Majordomo lists of VGER.KERNEL.ORG at:
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<http://vger.kernel.org/vger-lists.html>
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If changes affect userland-kernel interfaces, please send
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the MAN-PAGES maintainer (as listed in the MAINTAINERS file)
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a man-pages patch, or at least a notification of the change,
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so that some information makes its way into the manual pages.
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Even if the maintainer did not respond in step #4, make sure to ALWAYS
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copy the maintainer when you change their code.
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For small patches you may want to CC the Trivial Patch Monkey
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trivial@kernel.org managed by Adrian Bunk; which collects "trivial"
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patches. Trivial patches must qualify for one of the following rules:
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Spelling fixes in documentation
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Spelling fixes which could break grep(1)
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Warning fixes (cluttering with useless warnings is bad)
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Compilation fixes (only if they are actually correct)
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Runtime fixes (only if they actually fix things)
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Removing use of deprecated functions/macros (eg. check_region)
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Contact detail and documentation fixes
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Non-portable code replaced by portable code (even in arch-specific,
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since people copy, as long as it's trivial)
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Any fix by the author/maintainer of the file (ie. patch monkey
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in re-transmission mode)
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URL: <http://www.kernel.org/pub/linux/kernel/people/bunk/trivial/>
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7) No MIME, no links, no compression, no attachments. Just plain text.
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Linus and other kernel developers need to be able to read and comment
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on the changes you are submitting. It is important for a kernel
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developer to be able to "quote" your changes, using standard e-mail
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tools, so that they may comment on specific portions of your code.
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For this reason, all patches should be submitting e-mail "inline".
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WARNING: Be wary of your editor's word-wrap corrupting your patch,
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if you choose to cut-n-paste your patch.
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Do not attach the patch as a MIME attachment, compressed or not.
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Many popular e-mail applications will not always transmit a MIME
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attachment as plain text, making it impossible to comment on your
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code. A MIME attachment also takes Linus a bit more time to process,
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decreasing the likelihood of your MIME-attached change being accepted.
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Exception: If your mailer is mangling patches then someone may ask
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you to re-send them using MIME.
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WARNING: Some mailers like Mozilla send your messages with
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---- message header ----
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Content-Type: text/plain; charset=us-ascii; format=flowed
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---- message header ----
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The problem is that "format=flowed" makes some of the mailers
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on receiving side to replace TABs with spaces and do similar
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changes. Thus the patches from you can look corrupted.
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To fix this just make your mozilla defaults/pref/mailnews.js file to look like:
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pref("mailnews.send_plaintext_flowed", false); // RFC 2646=======
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pref("mailnews.display.disable_format_flowed_support", true);
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8) E-mail size.
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When sending patches to Linus, always follow step #7.
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Large changes are not appropriate for mailing lists, and some
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maintainers. If your patch, uncompressed, exceeds 40 kB in size,
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it is preferred that you store your patch on an Internet-accessible
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server, and provide instead a URL (link) pointing to your patch.
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9) Name your kernel version.
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It is important to note, either in the subject line or in the patch
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description, the kernel version to which this patch applies.
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If the patch does not apply cleanly to the latest kernel version,
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Linus will not apply it.
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10) Don't get discouraged. Re-submit.
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After you have submitted your change, be patient and wait. If Linus
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likes your change and applies it, it will appear in the next version
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of the kernel that he releases.
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However, if your change doesn't appear in the next version of the
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kernel, there could be any number of reasons. It's YOUR job to
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narrow down those reasons, correct what was wrong, and submit your
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updated change.
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It is quite common for Linus to "drop" your patch without comment.
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That's the nature of the system. If he drops your patch, it could be
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due to
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* Your patch did not apply cleanly to the latest kernel version.
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* Your patch was not sufficiently discussed on linux-kernel.
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* A style issue (see section 2).
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* An e-mail formatting issue (re-read this section).
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* A technical problem with your change.
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* He gets tons of e-mail, and yours got lost in the shuffle.
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* You are being annoying.
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When in doubt, solicit comments on linux-kernel mailing list.
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11) Include PATCH in the subject
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Due to high e-mail traffic to Linus, and to linux-kernel, it is common
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convention to prefix your subject line with [PATCH]. This lets Linus
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and other kernel developers more easily distinguish patches from other
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e-mail discussions.
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12) Sign your work
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To improve tracking of who did what, especially with patches that can
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percolate to their final resting place in the kernel through several
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layers of maintainers, we've introduced a "sign-off" procedure on
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patches that are being emailed around.
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The sign-off is a simple line at the end of the explanation for the
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patch, which certifies that you wrote it or otherwise have the right to
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pass it on as a open-source patch. The rules are pretty simple: if you
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can certify the below:
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Developer's Certificate of Origin 1.1
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By making a contribution to this project, I certify that:
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(a) The contribution was created in whole or in part by me and I
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have the right to submit it under the open source license
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indicated in the file; or
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(b) The contribution is based upon previous work that, to the best
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of my knowledge, is covered under an appropriate open source
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license and I have the right under that license to submit that
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work with modifications, whether created in whole or in part
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by me, under the same open source license (unless I am
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permitted to submit under a different license), as indicated
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in the file; or
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(c) The contribution was provided directly to me by some other
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person who certified (a), (b) or (c) and I have not modified
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it.
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(d) I understand and agree that this project and the contribution
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are public and that a record of the contribution (including all
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personal information I submit with it, including my sign-off) is
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maintained indefinitely and may be redistributed consistent with
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this project or the open source license(s) involved.
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then you just add a line saying
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Signed-off-by: Random J Developer <random@developer.example.org>
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using your real name (sorry, no pseudonyms or anonymous contributions.)
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Some people also put extra tags at the end. They'll just be ignored for
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now, but you can do this to mark internal company procedures or just
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point out some special detail about the sign-off.
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13) When to use Acked-by:
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The Signed-off-by: tag indicates that the signer was involved in the
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development of the patch, or that he/she was in the patch's delivery path.
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If a person was not directly involved in the preparation or handling of a
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patch but wishes to signify and record their approval of it then they can
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arrange to have an Acked-by: line added to the patch's changelog.
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Acked-by: is often used by the maintainer of the affected code when that
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maintainer neither contributed to nor forwarded the patch.
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Acked-by: is not as formal as Signed-off-by:. It is a record that the acker
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has at least reviewed the patch and has indicated acceptance. Hence patch
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mergers will sometimes manually convert an acker's "yep, looks good to me"
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into an Acked-by:.
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Acked-by: does not necessarily indicate acknowledgement of the entire patch.
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For example, if a patch affects multiple subsystems and has an Acked-by: from
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one subsystem maintainer then this usually indicates acknowledgement of just
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the part which affects that maintainer's code. Judgement should be used here.
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When in doubt people should refer to the original discussion in the mailing
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list archives.
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14) The canonical patch format
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The canonical patch subject line is:
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Subject: [PATCH 001/123] subsystem: summary phrase
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The canonical patch message body contains the following:
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- A "from" line specifying the patch author.
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- An empty line.
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- The body of the explanation, which will be copied to the
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permanent changelog to describe this patch.
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- The "Signed-off-by:" lines, described above, which will
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also go in the changelog.
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- A marker line containing simply "---".
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- Any additional comments not suitable for the changelog.
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- The actual patch (diff output).
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The Subject line format makes it very easy to sort the emails
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alphabetically by subject line - pretty much any email reader will
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support that - since because the sequence number is zero-padded,
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the numerical and alphabetic sort is the same.
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The "subsystem" in the email's Subject should identify which
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area or subsystem of the kernel is being patched.
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The "summary phrase" in the email's Subject should concisely
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describe the patch which that email contains. The "summary
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phrase" should not be a filename. Do not use the same "summary
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phrase" for every patch in a whole patch series (where a "patch
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series" is an ordered sequence of multiple, related patches).
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Bear in mind that the "summary phrase" of your email becomes
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a globally-unique identifier for that patch. It propagates
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all the way into the git changelog. The "summary phrase" may
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later be used in developer discussions which refer to the patch.
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People will want to google for the "summary phrase" to read
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discussion regarding that patch.
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A couple of example Subjects:
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Subject: [patch 2/5] ext2: improve scalability of bitmap searching
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Subject: [PATCHv2 001/207] x86: fix eflags tracking
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The "from" line must be the very first line in the message body,
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and has the form:
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From: Original Author <author@example.com>
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The "from" line specifies who will be credited as the author of the
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patch in the permanent changelog. If the "from" line is missing,
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then the "From:" line from the email header will be used to determine
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the patch author in the changelog.
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The explanation body will be committed to the permanent source
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changelog, so should make sense to a competent reader who has long
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since forgotten the immediate details of the discussion that might
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have led to this patch.
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The "---" marker line serves the essential purpose of marking for patch
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handling tools where the changelog message ends.
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One good use for the additional comments after the "---" marker is for
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a diffstat, to show what files have changed, and the number of inserted
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and deleted lines per file. A diffstat is especially useful on bigger
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patches. Other comments relevant only to the moment or the maintainer,
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not suitable for the permanent changelog, should also go here.
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Use diffstat options "-p 1 -w 70" so that filenames are listed from the
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top of the kernel source tree and don't use too much horizontal space
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(easily fit in 80 columns, maybe with some indentation).
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See more details on the proper patch format in the following
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references.
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-----------------------------------
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SECTION 2 - HINTS, TIPS, AND TRICKS
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-----------------------------------
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This section lists many of the common "rules" associated with code
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submitted to the kernel. There are always exceptions... but you must
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have a really good reason for doing so. You could probably call this
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section Linus Computer Science 101.
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1) Read Documentation/CodingStyle
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Nuff said. If your code deviates too much from this, it is likely
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to be rejected without further review, and without comment.
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Once significant exception is when moving code from one file to
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another in this case you should not modify the moved code at all in
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the same patch which moves it. This clearly delineates the act of
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moving the code and your changes. This greatly aids review of the
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actual differences and allows tools to better track the history of
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the code itself.
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Check your patches with the patch style checker prior to submission
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(scripts/checkpatch.pl). The style checker should be viewed as
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a guide not as the final word. If your code looks better with
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a violation then its probably best left alone.
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The checker reports at three levels:
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- ERROR: things that are very likely to be wrong
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- WARNING: things requiring careful review
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- CHECK: things requiring thought
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You should be able to justify all violations that remain in your
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patch.
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2) #ifdefs are ugly
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Code cluttered with ifdefs is difficult to read and maintain. Don't do
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it. Instead, put your ifdefs in a header, and conditionally define
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'static inline' functions, or macros, which are used in the code.
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Let the compiler optimize away the "no-op" case.
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Simple example, of poor code:
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dev = alloc_etherdev (sizeof(struct funky_private));
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if (!dev)
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return -ENODEV;
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#ifdef CONFIG_NET_FUNKINESS
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init_funky_net(dev);
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#endif
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Cleaned-up example:
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(in header)
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#ifndef CONFIG_NET_FUNKINESS
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static inline void init_funky_net (struct net_device *d) {}
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#endif
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|
|
|
(in the code itself)
|
|
dev = alloc_etherdev (sizeof(struct funky_private));
|
|
if (!dev)
|
|
return -ENODEV;
|
|
init_funky_net(dev);
|
|
|
|
|
|
|
|
3) 'static inline' is better than a macro
|
|
|
|
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.
|
|
|
|
Macros should only be used for cases where a static inline is clearly
|
|
suboptimal [there a few, isolated cases of this in fast paths],
|
|
or where it is impossible to use a static inline function [such as
|
|
string-izing].
|
|
|
|
'static inline' is preferred over 'static __inline__', 'extern inline',
|
|
and 'extern __inline__'.
|
|
|
|
|
|
|
|
4) Don't over-design.
|
|
|
|
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."
|
|
|
|
|
|
|
|
----------------------
|
|
SECTION 3 - REFERENCES
|
|
----------------------
|
|
|
|
Andrew Morton, "The perfect patch" (tpp).
|
|
<http://www.zip.com.au/~akpm/linux/patches/stuff/tpp.txt>
|
|
|
|
Jeff Garzik, "Linux kernel patch submission format".
|
|
<http://linux.yyz.us/patch-format.html>
|
|
|
|
Greg Kroah-Hartman, "How to piss off a kernel subsystem maintainer".
|
|
<http://www.kroah.com/log/2005/03/31/>
|
|
<http://www.kroah.com/log/2005/07/08/>
|
|
<http://www.kroah.com/log/2005/10/19/>
|
|
<http://www.kroah.com/log/2006/01/11/>
|
|
|
|
NO!!!! No more huge patch bombs to linux-kernel@vger.kernel.org people!
|
|
<http://marc.theaimsgroup.com/?l=linux-kernel&m=112112749912944&w=2>
|
|
|
|
Kernel Documentation/CodingStyle:
|
|
<http://sosdg.org/~coywolf/lxr/source/Documentation/CodingStyle>
|
|
|
|
Linus Torvalds's mail on the canonical patch format:
|
|
<http://lkml.org/lkml/2005/4/7/183>
|
|
--
|