Request inclusion of oneline summaries when referring to other commits Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
		
			
				
	
	
		
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			753 lines
		
	
	
	
		
			29 KiB
			
		
	
	
	
		
			Text
		
	
	
	
	
	
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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.
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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://userweb.kernel.org/~akpm/stuff/patch-scripts.tar.gz
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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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The maintainer will thank you if you write your patch description in a
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form which can be easily pulled into Linux's source code management
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system, git, as a "commit log".  See #15, below.
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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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When you submit or resubmit a patch or patch series, include the
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complete patch description and justification for it.  Don't just
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say that this is version N of the patch (series).  Don't expect the
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patch merger to refer back to earlier patch versions or referenced
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URLs to find the patch description and put that into the patch.
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I.e., the patch (series) and its description should be self-contained.
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This benefits both the patch merger(s) and reviewers.  Some reviewers
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probably didn't even receive earlier versions of the patch.
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If the patch fixes a logged bug entry, refer to that bug entry by
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number and URL.
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If you want to refer to a specific commit, don't just refer to the
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SHA-1 ID of the commit. Please also include the oneline summary of
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the commit, to make it easier for reviewers to know what it is about.
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Example:
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	Commit e21d2170f36602ae2708 ("video: remove unnecessary
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	platform_set_drvdata()") removed the unnecessary
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	platform_set_drvdata(), but left the variable "dev" unused,
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	delete it.
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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/checkpatch.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.  The script
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scripts/get_maintainer.pl can be very useful at this step.
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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 #5, 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 which collects "trivial" patches. Have a look
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into the MAINTAINERS file for its current manager.
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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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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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See Documentation/email-clients.txt for hints about configuring
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your e-mail client so that it sends your patches untouched.
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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 300 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 an 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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If you are a subsystem or branch maintainer, sometimes you need to slightly
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modify patches you receive in order to merge them, because the code is not
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exactly the same in your tree and the submitters'. If you stick strictly to
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rule (c), you should ask the submitter to rediff, but this is a totally
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counter-productive waste of time and energy. Rule (b) allows you to adjust
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the code, but then it is very impolite to change one submitter's code and
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make him endorse your bugs. To solve this problem, it is recommended that
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you add a line between the last Signed-off-by header and yours, indicating
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the nature of your changes. While there is nothing mandatory about this, it
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seems like prepending the description with your mail and/or name, all
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enclosed in square brackets, is noticeable enough to make it obvious that
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you are responsible for last-minute changes. Example :
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	Signed-off-by: Random J Developer <random@developer.example.org>
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	[lucky@maintainer.example.org: struct foo moved from foo.c to foo.h]
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	Signed-off-by: Lucky K Maintainer <lucky@maintainer.example.org>
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This practise is particularly helpful if you maintain a stable branch and
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want at the same time to credit the author, track changes, merge the fix,
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and protect the submitter from complaints. Note that under no circumstances
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can you change the author's identity (the From header), as it is the one
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which appears in the changelog.
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Special note to back-porters: It seems to be a common and useful practise
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to insert an indication of the origin of a patch at the top of the commit
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message (just after the subject line) to facilitate tracking. For instance,
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here's what we see in 2.6-stable :
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    Date:   Tue May 13 19:10:30 2008 +0000
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        SCSI: libiscsi regression in 2.6.25: fix nop timer handling
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        commit 4cf1043593db6a337f10e006c23c69e5fc93e722 upstream
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And here's what appears in 2.4 :
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    Date:   Tue May 13 22:12:27 2008 +0200
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        wireless, airo: waitbusy() won't delay
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        [backport of 2.6 commit b7acbdfbd1f277c1eb23f344f899cfa4cd0bf36a]
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Whatever the format, this information provides a valuable help to people
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tracking your trees, and to people trying to trouble-shoot bugs in your
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tree.
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13) When to use Acked-by: and Cc:
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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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If a person has had the opportunity to comment on a patch, but has not
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provided such comments, you may optionally add a "Cc:" tag to the patch.
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This is the only tag which might be added without an explicit action by the
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						|
person it names.  This tag documents that potentially interested parties
 | 
						|
have been included in the discussion
 | 
						|
 | 
						|
 | 
						|
14) Using Reported-by:, Tested-by:, Reviewed-by: and Suggested-by:
 | 
						|
 | 
						|
If this patch fixes a problem reported by somebody else, consider adding a
 | 
						|
Reported-by: tag to credit the reporter for their contribution.  Please
 | 
						|
note that this tag should not be added without the reporter's permission,
 | 
						|
especially if the problem was not reported in a public forum.  That said,
 | 
						|
if we diligently credit our bug reporters, they will, hopefully, be
 | 
						|
inspired to help us again in the future.
 | 
						|
 | 
						|
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 likelihood of your patch getting into the kernel.
 | 
						|
 | 
						|
A Suggested-by: tag indicates that the patch idea is suggested by the person
 | 
						|
named and ensures credit to the person for the idea. Please note that this
 | 
						|
tag should not be added without the reporter's permission, especially if the
 | 
						|
idea was not posted in a public forum. That said, if we diligently credit our
 | 
						|
idea reporters, they will, hopefully, be inspired to help us again in the
 | 
						|
future.
 | 
						|
 | 
						|
 | 
						|
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.  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
 | 
						|
--oneline".
 | 
						|
 | 
						|
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
 | 
						|
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
 | 
						|
the multiple versions of the patch have been sent out in response to
 | 
						|
comments (i.e., "v1, v2, v3"), or "RFC" to indicate a request for
 | 
						|
comments.  If there are four patches in a patch series the individual
 | 
						|
patches may be numbered like this: 1/4, 2/4, 3/4, 4/4.  This assures
 | 
						|
that developers understand the order in which the patches should be
 | 
						|
applied and that they have reviewed or applied all of the patches in
 | 
						|
the patch series.
 | 
						|
 | 
						|
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.  Including symptoms of the failure which the
 | 
						|
patch addresses (kernel log messages, oops messages, etc.) is
 | 
						|
especially useful for people who might be searching the commit logs
 | 
						|
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
 | 
						|
well as descriptive.
 | 
						|
 | 
						|
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.  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
 | 
						|
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.
 | 
						|
 | 
						|
 | 
						|
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
 | 
						|
 | 
						|
(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 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].
 | 
						|
 | 
						|
'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://userweb.kernel.org/~akpm/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/linux/maintainer.html>
 | 
						|
  <http://www.kroah.com/log/linux/maintainer-02.html>
 | 
						|
  <http://www.kroah.com/log/linux/maintainer-03.html>
 | 
						|
  <http://www.kroah.com/log/linux/maintainer-04.html>
 | 
						|
  <http://www.kroah.com/log/linux/maintainer-05.html>
 | 
						|
 | 
						|
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>
 | 
						|
 | 
						|
Andi Kleen, "On submitting kernel patches"
 | 
						|
  Some strategies to get difficult or controversial changes in.
 | 
						|
  http://halobates.de/on-submitting-patches.pdf
 | 
						|
 | 
						|
--
 |