1. 07 Feb, 2018 3 commits
  2. 03 Feb, 2018 1 commit
    • Linus Torvalds's avatar
      pinctrl: remove include file from <linux/device.h> · 23c35f48
      Linus Torvalds authored
      
      
      When pulling the recent pinctrl merge, I was surprised by how a
      pinctrl-only pull request ended up rebuilding basically the whole
      kernel.
      
      The reason for that ended up being that <linux/device.h> included
      <linux/pinctrl/devinfo.h>, so any change to that file ended up causing
      pretty much every driver out there to be rebuilt.
      
      The reason for that was because 'struct device' has this in it:
      
          #ifdef CONFIG_PINCTRL
              struct dev_pin_info     *pins;
          #endif
      
      but we already avoid header includes for these kinds of things in that
      header file, preferring to just use a forward-declaration of the
      structure instead.  Exactly to avoid this kind of header dependency.
      
      Since some drivers seem to expect that <linux/pinctrl/devinfo.h> header
      to come in automatically, move the include to <linux/pinctrl/pinctrl.h>
      instead.  It might be better to just make the includes more targeted,
      but I'm not going to review every driver.
      
      It would definitely be good to have a tool for finding and minimizing
      header dependencies automatically - or at least help with them.  Right
      now we almost certainly end up having way too many of these things, and
      it's hard to test every single configuration.
      
      FWIW, you can get a sense of the "hotness" of a header file with something
      like this after doing a full build:
      
          find . -name '.*.o.cmd' -print0 |
              xargs -0 tail --lines=+2 |
              grep -v 'wildcard ' |
              tr ' \\' '\n' |
              sort | uniq -c | sort -n | less -S
      
      which isn't exact (there are other things in those '*.o.cmd' than just
      the dependencies, and the "--lines=+2" only removes the header), but
      might a useful approximation.
      
      With this patch, <linux/pinctrl/devinfo.h> drops to "only" having 833
      users in the current x86-64 allmodconfig.  In contrast, <linux/device.h>
      has 14857 build files including it directly or indirectly.
      
      Of course, the headers that absolutely _everybody_ includes (things like
      <linux/types.h> etc) get a score of 23000+.
      
      Cc: Linus Walleij <linus.walleij@linaro.org>
      Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      23c35f48
  3. 02 Feb, 2018 3 commits
  4. 01 Feb, 2018 33 commits