604 lines
22 KiB
Plaintext
604 lines
22 KiB
Plaintext
|
|
How to Get Your Change Into the Linux Kernel
|
|
or
|
|
Care And Operation Of Your Linus Torvalds
|
|
|
|
|
|
|
|
For a person or company who wishes to submit a change to the Linux
|
|
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.
|
|
|
|
|
|
|
|
--------------------------------------------
|
|
SECTION 1 - CREATING AND SENDING YOUR CHANGE
|
|
--------------------------------------------
|
|
|
|
|
|
|
|
1) "diff -up"
|
|
------------
|
|
|
|
Use "diff -up" or "diff -uprN" to create patches.
|
|
|
|
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
|
|
in "unified diff" format, as supplied by the '-u' argument to 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-2.6
|
|
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-2.6
|
|
|
|
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
|
|
|
|
"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. For earlier kernel versions, you can get it
|
|
from <http://www.xenotime.net/linux/doc/dontdiff>.
|
|
|
|
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-
|
|
generated it with diff(1), to ensure accuracy.
|
|
|
|
If your changes produce a lot of deltas, you may want to look into
|
|
splitting them into individual patches which modify things in
|
|
logical stages. This will facilitate easier reviewing by other
|
|
kernel developers, very important if you want your patch accepted.
|
|
There are a number of scripts which can aid in this:
|
|
|
|
Quilt:
|
|
http://savannah.nongnu.org/projects/quilt
|
|
|
|
Andrew Morton's patch scripts:
|
|
http://www.zip.com.au/~akpm/linux/patches/
|
|
Instead of these scripts, quilt is the recommended patch management
|
|
tool (see above).
|
|
|
|
|
|
|
|
2) Describe your changes.
|
|
|
|
Describe the technical detail of the change(s) your patch includes.
|
|
|
|
Be as specific as possible. The WORST descriptions possible include
|
|
things like "update driver X", "bug fix for driver X", or "this patch
|
|
includes updates for subsystem X. Please apply."
|
|
|
|
If your description starts to get long, that's a sign that you probably
|
|
need to split up your patch. See #3, next.
|
|
|
|
|
|
|
|
3) Separate your changes.
|
|
|
|
Separate _logical changes_ into a single patch file.
|
|
|
|
For example, if your changes include both bug fixes and performance
|
|
enhancements for a single driver, separate those changes into two
|
|
or more patches. If your changes include an API update, and a new
|
|
driver which uses that new API, separate those into two patches.
|
|
|
|
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.
|
|
|
|
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.
|
|
|
|
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.
|
|
|
|
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.
|
|
|
|
|
|
|
|
5) Select e-mail destination.
|
|
|
|
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.
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
|
6) Select your CC (e-mail carbon copy) list.
|
|
|
|
Unless you have a reason NOT to do so, CC linux-kernel@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.
|
|
|
|
Majordomo lists of VGER.KERNEL.ORG at:
|
|
<http://vger.kernel.org/vger-lists.html>
|
|
|
|
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 #4, make sure to ALWAYS
|
|
copy the maintainer when you change their code.
|
|
|
|
For small patches you may want to CC the Trivial Patch Monkey
|
|
trivial@kernel.org managed by Adrian Bunk; which collects "trivial"
|
|
patches. Trivial patches must qualify for one of the following rules:
|
|
Spelling fixes in documentation
|
|
Spelling fixes 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)
|
|
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)
|
|
URL: <http://www.kernel.org/pub/linux/kernel/people/bunk/trivial/>
|
|
|
|
|
|
|
|
7) 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 submitting e-mail "inline".
|
|
WARNING: Be wary of your editor's word-wrap corrupting your patch,
|
|
if you choose to cut-n-paste your patch.
|
|
|
|
Do not attach the patch as a MIME attachment, compressed or not.
|
|
Many popular e-mail applications will not always transmit a MIME
|
|
attachment as plain text, making it impossible to comment on your
|
|
code. A MIME attachment also takes Linus a bit more time to process,
|
|
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 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.
|
|
|
|
Large changes are not appropriate for mailing lists, and some
|
|
maintainers. If your patch, uncompressed, exceeds 40 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.
|
|
|
|
|
|
|
|
9) 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.
|
|
|
|
If the patch does not apply cleanly to the latest kernel version,
|
|
Linus will not apply it.
|
|
|
|
|
|
|
|
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
|
|
|
|
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.
|
|
|
|
|
|
|
|
12) 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
|
|
layers of maintainers, we've introduced a "sign-off" procedure on
|
|
patches that are being emailed around.
|
|
|
|
The sign-off is a simple line at the end of the explanation for the
|
|
patch, which certifies that you wrote it or otherwise have the right to
|
|
pass it on as a open-source patch. The rules are pretty simple: if you
|
|
can certify the below:
|
|
|
|
Developer's Certificate of Origin 1.1
|
|
|
|
By making a contribution to this project, I certify that:
|
|
|
|
(a) The contribution was created in whole or in part by me and I
|
|
have the right to submit it under the open source license
|
|
indicated in the file; or
|
|
|
|
(b) The contribution is based upon previous work that, to the best
|
|
of my knowledge, is covered under an appropriate open source
|
|
license and I have the right under that license to submit that
|
|
work with modifications, whether created in whole or in part
|
|
by me, under the same open source license (unless I am
|
|
permitted to submit under a different license), as indicated
|
|
in the file; or
|
|
|
|
(c) The contribution was provided directly to me by some other
|
|
person who certified (a), (b) or (c) and I have not modified
|
|
it.
|
|
|
|
(d) I understand and agree that this project and the contribution
|
|
are public and that a record of the contribution (including all
|
|
personal information I submit with it, including my sign-off) is
|
|
maintained indefinitely and may be redistributed consistent with
|
|
this project or the open source license(s) involved.
|
|
|
|
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.)
|
|
|
|
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.
|
|
|
|
|
|
13) 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.
|
|
|
|
Acked-by: is often used by the maintainer of the affected code when that
|
|
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:.
|
|
|
|
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.
|
|
|
|
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
|
|
|
|
|
|
14) Using Test-by: and Reviewed-by:
|
|
|
|
A Tested-by: tag indicates that the patch has been successfully tested (in
|
|
some environment) by the person named. This tag informs maintainers that
|
|
some testing has been performed, provides a means to locate testers for
|
|
future patches, and ensures credit for the testers.
|
|
|
|
Reviewed-by:, instead, indicates that the patch has been reviewed and found
|
|
acceptable according to the Reviewer's Statement:
|
|
|
|
Reviewer's statement of oversight
|
|
|
|
By offering my Reviewed-by: tag, I state that:
|
|
|
|
(a) I have carried out a technical review of this patch to
|
|
evaluate its appropriateness and readiness for inclusion into
|
|
the mainline kernel.
|
|
|
|
(b) Any problems, concerns, or questions relating to the patch
|
|
have been communicated back to the submitter. I am satisfied
|
|
with the submitter's response to my comments.
|
|
|
|
(c) While there may be things that could be improved with this
|
|
submission, I believe that it is, at this time, (1) a
|
|
worthwhile modification to the kernel, and (2) free of known
|
|
issues which would argue against its inclusion.
|
|
|
|
(d) While I have reviewed the patch and believe it to be sound, I
|
|
do not (unless explicitly stated elsewhere) make any
|
|
warranties or guarantees that it will achieve its stated
|
|
purpose or function properly in any given situation.
|
|
|
|
A Reviewed-by tag is a statement of opinion that the patch is an
|
|
appropriate modification of the kernel without any remaining serious
|
|
technical issues. Any interested reviewer (who has done the work) can
|
|
offer a Reviewed-by tag for a patch. This tag serves to give credit to
|
|
reviewers and to inform maintainers of the degree of review which has been
|
|
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 liklihood of your patch getting into the kernel.
|
|
|
|
|
|
15) The canonical patch format
|
|
|
|
The canonical patch subject line is:
|
|
|
|
Subject: [PATCH 001/123] subsystem: summary phrase
|
|
|
|
The canonical patch message body contains the following:
|
|
|
|
- A "from" line specifying the patch author.
|
|
|
|
- An empty line.
|
|
|
|
- The body of the explanation, which will be copied to the
|
|
permanent changelog to describe this patch.
|
|
|
|
- The "Signed-off-by:" lines, described above, which will
|
|
also go in the changelog.
|
|
|
|
- A marker line containing simply "---".
|
|
|
|
- Any additional comments not suitable for the changelog.
|
|
|
|
- The actual patch (diff output).
|
|
|
|
The Subject line format makes it very easy to sort the emails
|
|
alphabetically by subject line - pretty much any email reader will
|
|
support that - since because the sequence number is zero-padded,
|
|
the numerical and alphabetic sort is the same.
|
|
|
|
The "subsystem" in the email's Subject should identify which
|
|
area or subsystem of the kernel is being patched.
|
|
|
|
The "summary phrase" in the email's Subject should concisely
|
|
describe the patch which that email contains. The "summary
|
|
phrase" should not be a filename. Do not use the same "summary
|
|
phrase" for every patch in a whole patch series (where a "patch
|
|
series" is an ordered sequence of multiple, related patches).
|
|
|
|
Bear in mind that the "summary phrase" of your email becomes
|
|
a globally-unique identifier for that patch. It propagates
|
|
all the way into the git changelog. The "summary phrase" may
|
|
later be used in developer discussions which refer to the patch.
|
|
People will want to google for the "summary phrase" to read
|
|
discussion regarding that patch.
|
|
|
|
A couple of example Subjects:
|
|
|
|
Subject: [patch 2/5] ext2: improve scalability of bitmap searching
|
|
Subject: [PATCHv2 001/207] x86: fix eflags tracking
|
|
|
|
The "from" line must be the very first line in the message body,
|
|
and has the form:
|
|
|
|
From: Original Author <author@example.com>
|
|
|
|
The "from" line specifies who will be credited as the author of the
|
|
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.
|
|
|
|
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.
|
|
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).
|
|
|
|
See more details on the proper patch format in the following
|
|
references.
|
|
|
|
|
|
|
|
|
|
-----------------------------------
|
|
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
|
|
|
|
(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://users.sosdg.org/~qiyong/lxr/source/Documentation/CodingStyle>
|
|
|
|
Linus Torvalds's mail on the canonical patch format:
|
|
<http://lkml.org/lkml/2005/4/7/183>
|
|
--
|