--------------------------------------------
+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
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()")
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-
-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.
-
-
+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.
-6) Select your CC (e-mail carbon copy) list.
+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.
-Unless you have a reason NOT to do so, CC linux-kernel@vger.kernel.org.
+Patches that fix a severe bug in a released kernel should be directed
+toward the stable maintainers by putting a line like this:
-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.
+ Cc: stable@vger.kernel.org
-Majordomo lists of VGER.KERNEL.ORG at:
- <http://vger.kernel.org/vger-lists.html>
+into your patch.
-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.
+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.
-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)
-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
See Documentation/email-clients.txt for hints about configuring
your e-mail client so that it sends your patches untouched.
-8) E-mail size.
+7) E-mail size.
When sending patches to Linus, always follow step #7.
-9) Name your kernel version.
+8) Name your kernel version.
It is important to note, either in the subject line or in the patch
description, the kernel version to which this patch applies.
-10) Don't get discouraged. Re-submit.
+9) 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
-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
-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
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
[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.
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
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:
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.
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.
+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).
projects / cascardo / linux.git / blobdiff