how do you find the subsystem of a file?

i wrote a patch that got rejected because it did not apply cleanly to the tree of greg kh
https://lkml.org/lkml/2021/8/18/304

the file i modified is
drivers/staging/rtl8723bs/include/rtl8192c_recv.h

get_maintainer.pl gave me the list of emails to send the patch to, and i used it for that purpose. the file Documentation/process/submitting-patches.rst says to see the T: entry for the subsystem in MAINTAINERS to find the right tree to base the patch on. i tried searching through MAINTAINERS and found that there are a few subsystems that start with RTL8*.

greg kh is listed a few times in MAINTAINERS, so i'm not able to find the exact tree to start with by looking for the maintainer.

is there a systematic way of finding the subsystem, given a file?

in addition, how do i know what branch to use? the T: entries have a repo, but not a branch name.

thanks!
:wq, danny

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answering my own question,

the output of

git log --oneline -1 <path>

should have the subsystem listed at the beginning.

thanks!

C-x C-c, danny

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If there's no better entry listed in a T:, the linux-next tree is a good default. Failing that, a recent pull of Linus's tree is usually OK (though can cause issues with conflicts if other people are working on the area and their patches are in linux-next already). Since the linux-next tree is rebuild every day, it's usually only 24 hours or so behind the 200+ maintainer trees that feed it.

The quick cheat sheet for linux-next:

$ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git

$ git remote add linux-next git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
$ git fetch linux-next
$ git fetch --tags linux-next
... # later on
$ git remote update

$ git checkout next-20210820 (or whatever the one you want is)

Don't use 'git pull' against a linux-next tree, as it won't do what you want, use 'remote update'. (The gory details - it rebases every day due to the way it is built)

Also, you can bisect between a 'next-20210605' tag and a Linus 'v5.13-rc3' type tag, but bisecting between two 'next-mmm' tags will fail, for the same reasons that git pull will blow chunks.

You want it pointing at master/HEAD unless you have a *damned* good reason to use something else (usually "maintainer specifically told you to use a different branch")

Actually, it's not *necessarily* 'subsystem' - it's "what the tree maintainer wants as the start of the Subject: line", which can sometimes be different.

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Yes, use the tool you already used:

$ ./scripts/get_maintainer.pl drivers/staging/rtl8723bs/include/rtl8192c_recv.h
Greg Kroah-Hartman <[email protected]> (supporter:STAGING SUBSYSTEM)
[email protected] (open list:STAGING SUBSYSTEM)
[email protected] (open list)

That shows this file is in the staging subsystem, and there's the list to send the patch to, as well as the person you should cc: on it.

You can always ask the subsystem maintainer about what branch to use if you have a question.

thanks,

greg k-h

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