|| ||Theodore Ts'o <tytso-AT-mit.edu> |
|| ||Linus Torvalds <torvalds-AT-linux-foundation.org> |
|| ||[PATCH] Documentation: Add "how to write a good patch summary" to SubmittingPatches |
|| ||Thu, 16 Apr 2009 07:44:45 -0400|
|| ||Linux Kernel Developers List <linux-kernel-AT-vger.kernel.org>,
Theodore Ts'o <tytso-AT-mit.edu>, Ingo Molnar <mingo-AT-elte.hu>|
|| ||Article, Thread
Unfortunately many patch submissions are arriving with painfully poor
patch descriptions. As a result of the discussion on LKML:
explain how to submit a better patch description, in the (perhaps
vain) hope that maintainers won't end up having to rewrite the git
commit logs as often as they do today.
Signed-off-by: "Theodore Ts'o" <email@example.com>
Cc: Ingo Molnar <firstname.lastname@example.org>
I don't describe the "Impact: " header, since this is still somewhat
controversial. But even if we don't end up standardizing on Impact:,
there is good information that we should be telling people about.
Also, SubmittingPatches is getting quite long. It probably needs to be
split up into a couple of different files, or at least reorganized for
easier reading. It's not clear to me that trying to explain how to
develop a good patch, how to write a good patch submission, and issues
around the Developers Certification of Origin should be smushed together
all into a single documentation file. But, that reorg is for another
day and another patch.
Documentation/SubmittingPatches | 65 ++++++++++++++++++++++++++++++--------
1 files changed, 51 insertions(+), 14 deletions(-)
diff --git a/Documentation/SubmittingPatches b/Documentation/SubmittingPatches
index f309d3c..b6f463f 100644
@@ -91,6 +91,10 @@ 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."
+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.
If your description starts to get long, that's a sign that you probably
need to split up your patch. See #3, next.
@@ -485,12 +489,33 @@ 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.
+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
+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
+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:
@@ -510,19 +535,31 @@ 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.
+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.
-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).
+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
+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
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