- How to Get Your Change Into the Linux Kernel
- or
- Care And Operation Of Your Linus Torvalds
-
-
+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
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
---------------------------------------------
+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:
+which can be grabbed with::
- git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
+ 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
+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"
-------------
+1) ``diff -up``
+---------------
-If you must generate your patches by hand, use "diff -up" or "diff -uprN"
+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
-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
+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:
+To create a patch for a single file, it is often sufficient to do::
SRCTREE= linux
MYFILE= drivers/net/mydriver.c
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:
+own source tree. For example::
MYSRC= /devel/linux
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
+``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.
generating it with diff(1), to ensure accuracy.
If your changes produce a lot of deltas, you need to split them into
-individual patches which modify things in logical stages; see section
-#3. This will facilitate review by other kernel developers,
+individual patches which modify things in logical stages; see
+:ref:`split_changes`. This will facilitate review by other kernel developers,
very important if you want your patch accepted.
-If you're using git, "git rebase -i" can help you with this process. If
+If you're using git, ``git rebase -i`` can help you with this process. If
you're not using git, quilt <http://savannah.nongnu.org/projects/quilt>
is another popular alternative.
+.. _describe_changes:
-
-2) Describe your changes.
--------------------------
+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
The maintainer will thank you if you write your patch description in a
form which can be easily pulled into Linux's source code management
-system, git, as a "commit log". See #15, below.
+system, git, as a "commit log". See :ref:`explicit_in_reply_to`.
Solve only one problem per patch. If your description starts to get
long, that's a sign that you probably need to split up your patch.
-See #3, next.
+See :ref:`split_changes`.
When you submit or resubmit a patch or patch series, include the
complete patch description and justification for it. Don't just
If you want to refer to a specific commit, don't just refer to the
SHA-1 ID of the commit. Please also include the oneline summary of
the commit, to make it easier for reviewers to know what it is about.
-Example:
+Example::
Commit e21d2170f36602ae2708 ("video: remove unnecessary
platform_set_drvdata()") removed the unnecessary
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. For example:
+SHA-1 ID, and the one line summary. For example::
Fixes: e21d2170f366 ("video: remove unnecessary platform_set_drvdata()")
The following git-config settings can be used to add a pretty format for
-outputting the above style in the git log or git show commands
+outputting the above style in the git log or git show commands::
[core]
abbrev = 12
[pretty]
fixes = Fixes: %h (\"%s\")
-3) Separate your changes.
--------------------------
+.. _split_changes:
+
+3) Separate your changes
+------------------------
-Separate each _logical change_ into a separate patch.
+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
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"
+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
+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.
-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
patch.
-5) Select the recipients for your patch.
-----------------------------------------
+5) Select the recipients for your patch
+---------------------------------------
You should always copy the appropriate subsystem maintainer(s) on any patch
to code that they maintain; look through the MAINTAINERS file and the
obviously, the patch should not be sent to any public lists.
Patches that fix a severe bug in a released kernel should be directed
-toward the stable maintainers by putting a line like this:
+toward the stable maintainers by putting a line like this::
Cc: stable@vger.kernel.org
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.
+linux-api@vger.kernel.org.
For small patches you may want to CC the Trivial Patch Monkey
trivial@kernel.org which collects "trivial" patches. Have a look
into the MAINTAINERS file for its current manager.
+
Trivial patches must qualify for one of the following rules:
+
Spelling fixes in documentation
Spelling fixes for errors which could break grep(1)
Warning fixes (cluttering with useless warnings is bad)
-6) 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.
-7) E-mail size.
----------------
+7) E-mail size
+--------------
Large changes are not appropriate for mailing lists, and some
maintainers. If your patch, uncompressed, exceeds 300 kB in size,
that if your patch exceeds 300 kB, it almost certainly needs to be broken up
anyway.
-8) Respond to review comments.
-------------------------------
+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;
politely and address the problems they have pointed out.
-9) Don't get discouraged - or impatient.
-----------------------------------------
+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.
pass it on as an open-source patch. The rules are pretty simple: if you
can certify the below:
- Developer's Certificate of Origin 1.1
+Developer's Certificate of Origin 1.1
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
- By making a contribution to this project, I certify that:
+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
maintained indefinitely and may be redistributed consistent with
this project or the open source license(s) involved.
-then you just add a line saying
+then you just add a line saying::
Signed-off-by: Random J Developer <random@developer.example.org>
the nature of your changes. While there is nothing mandatory about this, it
seems like prepending the description with your mail and/or name, all
enclosed in square brackets, is noticeable enough to make it obvious that
-you are responsible for last-minute changes. Example :
+you are responsible for last-minute changes. Example::
Signed-off-by: Random J Developer <random@developer.example.org>
[lucky@maintainer.example.org: struct foo moved from foo.c to foo.h]
Special note to back-porters: It seems to be a common and useful practice
to insert an indication of the origin of a patch at the top of the commit
message (just after the subject line) to facilitate tracking. For instance,
-here's what we see in a 3.x-stable release:
+here's what we see in a 3.x-stable release::
-Date: Tue Oct 7 07:26:38 2014 -0400
+ Date: Tue Oct 7 07:26:38 2014 -0400
libata: Un-break ATA blacklist
commit 1c40279960bcd7d52dbdf1d466b20d24b99176c8 upstream.
-And here's what might appear in an older kernel once a patch is backported:
+And here's what might appear in an older kernel once a patch is backported::
Date: Tue May 13 22:12:27 2008 +0200
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.
+provided such comments, you may optionally add a ``Cc:`` tag to the patch.
This is the only tag which might be added without an explicit action by the
person it names - but it should indicate that this person was copied on the
patch. This tag documents that potentially interested parties
Reviewed-by:, instead, indicates that the patch has been reviewed and found
acceptable according to the Reviewer's Statement:
- Reviewer's statement of oversight
+Reviewer's statement of oversight
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
- By offering my Reviewed-by: tag, I state that:
+By offering my Reviewed-by: tag, I state that:
- (a) I have carried out a technical review of this patch to
+ (a) I have carried out a technical review of this patch to
evaluate its appropriateness and readiness for inclusion into
the mainline kernel.
is used to make it easy to determine where a bug originated, which can help
review a bug fix. This tag also assists the stable kernel team in determining
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.
+method for indicating a bug fixed by the patch. See :ref:`describe_changes`
+for more details.
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
+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 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 (only needed if the person
+ - A ``from`` line specifying the patch author (only needed if the person
sending the patch is not the author).
- An empty line.
- The body of the explanation, line wrapped at 75 columns, which will
be copied to the permanent changelog to describe this patch.
- - The "Signed-off-by:" lines, described above, which will
+ - The ``Signed-off-by:`` lines, described above, which will
also go in the changelog.
- - A marker line containing simply "---".
+ - A marker line containing simply ``---``.
- Any additional comments not suitable for the changelog.
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
+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).
+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
+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
+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
+google for the ``summary phrase`` to read discussion regarding that
patch. It will also be the only thing that people may quickly see
when, two or three months later, they are going through perhaps
-thousands of patches using tools such as "gitk" or "git log
+thousands of patches using tools such as ``gitk`` or "git log
--oneline".
-For these reasons, the "summary" must be no more than 70-75
+For these reasons, the ``summary`` must be no more than 70-75
characters, and it must describe both what the patch changes, as well
as why the patch might be necessary. It is challenging to be both
succinct and descriptive, but that is what a well-written summary
should do.
-The "summary phrase" may be prefixed by tags enclosed in square
+The ``summary phrase`` may be prefixed by tags enclosed in square
brackets: "Subject: [PATCH <tag>...] <summary phrase>". The tags are
not considered part of the summary phrase, but describe how the patch
should be treated. Common tags might include a version descriptor if
applied and that they have reviewed or applied all of the patches in
the patch series.
-A couple of example Subjects:
+A couple of example Subjects::
Subject: [PATCH 2/5] ext2: improve scalability of bitmap searching
Subject: [PATCH v2 01/27] x86: fix eflags tracking
-The "from" line must be the very first line in the message body,
+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 ``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
looking for the applicable patch. If a patch fixes a compile failure,
it may not be necessary to include _all_ of the compile failures; just
enough that it is likely that someone searching for the patch can find
-it. As in the "summary phrase", it is important to be both succinct as
+it. As in the ``summary phrase``, it is important to be both succinct as
well as descriptive.
-The "---" marker line serves the essential purpose of marking for patch
+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
+One good use for the additional comments after the ``---`` marker is for
a diffstat, to show what files have changed, and the number of
inserted and deleted lines per file. A diffstat is especially useful
on bigger patches. Other comments relevant only to the moment or the
maintainer, not suitable for the permanent changelog, should also go
-here. A good example of such comments might be "patch changelogs"
+here. A good example of such comments might be ``patch changelogs``
which describe what has changed between the v1 and v2 version of the
patch.
-If you are going to include a diffstat after the "---" marker, please
-use diffstat options "-p 1 -w 70" so that filenames are listed from
+If you are going to include a diffstat after the ``---`` marker, please
+use diffstat options ``-p 1 -w 70`` so that filenames are listed from
the top of the kernel source tree and don't use too much horizontal
space (easily fit in 80 columns, maybe with some indentation). (git
generates appropriate diffstats by default.)
See more details on the proper patch format in the following
references.
+.. _explicit_in_reply_to:
+
15) Explicit In-Reply-To headers
--------------------------------
It can be helpful to manually add In-Reply-To: headers to a patch
-(e.g., when using "git send-email") to associate the patch with
+(e.g., when using ``git send-email``) to associate the patch with
previous relevant discussion, e.g. to link a bug fix to the email with
the bug report. However, for a multi-patch series, it is generally
best to avoid using In-Reply-To: to link to older versions of the
the cover email text) to link to an earlier version of the patch series.
-16) Sending "git pull" requests
--------------------------------
+16) Sending ``git pull`` requests
+---------------------------------
If you have a series of patches, it may be most convenient to have the
maintainer pull them directly into the subsystem repository with a
-"git pull" operation. Note, however, that pulling patches from a developer
+``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
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:
+interest on a single line; it should look something like::
Please pull from
to get these changes:
A pull request should also include an overall message saying what will be
-included in the request, a "git shortlog" listing of the patches
+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.
+git do it for you with the ``git request-pull`` command.
Some maintainers (including Linus) want to see pull requests from signed
commits; that increases their confidence that the request actually came
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
+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
public tree.
When generating your pull request, use the signed tag as the target. A
-command like this will do the trick:
+command like this will do the trick::
git request-pull master git://my.public.tree/linux.git my-signed-tag
-----------------------
-SECTION 2 - REFERENCES
-----------------------
+REFERENCES
+**********
Andrew Morton, "The perfect patch" (tpp).
<http://www.ozlabs.org/~akpm/stuff/tpp.txt>
Some strategies to get difficult or controversial changes in.
http://halobates.de/on-submitting-patches.pdf
---
projects / GitHub / moto-9609 / android_kernel_motorola_exynos9610.git / commitdiff