tree 634e94b991a6a34f9a92d6e1c73ac676737efd19
parent 90db76e829479ef2ba1fed8f2552846015469831
parent efaa14c7e981bdf8d3c8d39d3ed12bdc60faabb8
author Linus Torvalds <torvalds@linux-foundation.org> 1374426664 -0700
committer Linus Torvalds <torvalds@linux-foundation.org> 1374426664 -0700
mergetag object efaa14c7e981bdf8d3c8d39d3ed12bdc60faabb8
 type commit
 tag acpi-video-3.11
 tagger Rafael J. Wysocki <rjw@sisk.pl> 1374365243 +0200
 
 ACPI video support fixes for 3.11
 
 - Change from Aaron Lu makes ACPICA export a variable which can be
   used by driver code to determine whether or not the BIOS believes
   that we are compatible with Windows 8.
 
 - Change from Matthew Garrett makes the ACPI video driver initialize
   the ACPI backlight even if it is not going to be used afterward
   (that is needed for backlight control to work on Thinkpads).
 
 - Fix from Rafael J Wysocki implements Windows 8 backlight support
   workaround making i915 take over bakclight control if the firmware
   thinks it's dealing with Windows 8.  Based on the work of multiple
   developers including Matthew Garrett, Chun-Yi Lee, Seth Forshee,
   and Aaron Lu.
 
 - Fix from Aaron Lu makes the kernel follow Windows 8 by informing
   the firmware through the _DOS method that it should not carry out
   automatic brightness changes, so that brightness can be controlled
   by GUI.
 
 /
 -----BEGIN PGP SIGNATURE-----
 Version: GnuPG v2.0.19 (GNU/Linux)
 
 iQIcBAABAgAGBQJR6yY7AAoJEKhOf7ml8uNsbGUQAIVXwX8HF+9AOnqEIQYEaBiF
 HqfLDtHS5qobraK06auF/YmVaA17RdUnHssTuGiEbtIxpiUbuLPJaecZ9BeAf0Pz
 V4Y2IxF27aF9TDZrzkZXHcnYflzQ/kxj36eR9AmM2vSXmKZKxhfqLMeihVh2GgMv
 IlOs9PltK2GNX6C/CzjUQuUj4TYw8yxXsG93Gta0Z8scmxR7mpq9a9d0cPU/TjN/
 iatIhZLFU8ujp8xFiG9MDeG948AtperLu3g0v1D4mPnkmDJTuyMuE3FiioKL2zMY
 7jh6mDPkWUYdjdZkJcmyzgKZh5lAlZIJTZnJV6TrW5fjIpUz5F8XeD4ArMVU/u+A
 smro6XFcpgToRZTtmaEuraxzJHCS44FTjlXyH01FSIiN/Ll6YKyxDYsAzz4Z2sf6
 X5BJofAAiRelZh/o1MaMQzs3QeTUo44TaboGr2zka0cQ37KK9+8YRGYqcWo/BvGs
 sicgFKMeA6SANxHnCVNTslQzMYFrPp4yyMEu4gD7EE+U7cG6FSVhVHQjjTO9CmBd
 ZnX2EDX0Uy+oHTQ9BkyjWAD7rXF6StnOm37FPWHNZ+HnplHEoQQAn+vXsSfl9tbO
 7CPefZ/LQQEo1PZwLLkxruZ67NgxOd8/9I/aVjLUKgd8CDjez0UJVJ65gIXl1J4V
 kvaDy6faYTnUF8h/AYJf
 =vlwF
 -----END PGP SIGNATURE-----

Merge tag 'acpi-video-3.11' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm

Pull ACPI video support fixes from Rafael Wysocki:
 "I'm sending a separate pull request for this as it may be somewhat
  controversial.  The breakage addressed here is not really new and the
  fixes may not satisfy all users of the affected systems, but we've had
  so much back and forth dance in this area over the last several weeks
  that I think it's time to actually make some progress.

  The source of the problem is that about a year ago we started to tell
  BIOSes that we're compatible with Windows 8, which we really need to
  do, because some systems shipping with Windows 8 are tested with it
  and nothing else, so if we tell their BIOSes that we aren't compatible
  with Windows 8, we expose our users to untested BIOS/AML code paths.

  However, as it turns out, some Windows 8-specific AML code paths are
  not tested either, because Windows 8 actually doesn't use the ACPI
  methods containing them, so if we declare Windows 8 compatibility and
  attempt to use those ACPI methods, things break.  That occurs mostly
  in the backlight support area where in particular the _BCM and _BQC
  methods are plain unusable on some systems if the OS declares Windows
  8 compatibility.

  [ The additional twist is that they actually become usable if the OS
    says it is not compatible with Windows 8, but that may cause
    problems to show up elsewhere ]

  Investigation carried out by Matthew Garrett indicates that what
  Windows 8 does about backlight is to leave backlight control up to
  individual graphics drivers.  At least there's evidence that it does
  that if the Intel graphics driver is used, so we've decided to follow
  Windows 8 in that respect and allow i915 to control backlight (Daniel
  likes that part).

  The first commit from Aaron Lu makes ACPICA export the variable from
  which we can infer whether or not the BIOS believes that we are
  compatible with Windows 8.

  The second commit from Matthew Garrett prepares the ACPI video driver
  by making it initialize the ACPI backlight even if it is not going to
  be used afterward (that is needed for backlight control to work on
  Thinkpads).

  The third commit implements the actual workaround making i915 take
  over backlight control if the firmware thinks it's dealing with
  Windows 8 and is based on the work of multiple developers, including
  Matthew Garrett, Chun-Yi Lee, Seth Forshee, and Aaron Lu.

  The final commit from Aaron Lu makes us follow Windows 8 by informing
  the firmware through the _DOS method that it should not carry out
  automatic brightness changes, so that brightness can be controlled by
  GUI.

  Hopefully, this approach will allow us to avoid using blacklists of
  systems that should not declare Windows 8 compatibility just to avoid
  backlight control problems in the future.

   - Change from Aaron Lu makes ACPICA export a variable which can be
     used by driver code to determine whether or not the BIOS believes
     that we are compatible with Windows 8.

   - Change from Matthew Garrett makes the ACPI video driver initialize
     the ACPI backlight even if it is not going to be used afterward
     (that is needed for backlight control to work on Thinkpads).

   - Fix from Rafael J Wysocki implements Windows 8 backlight support
     workaround making i915 take over bakclight control if the firmware
     thinks it's dealing with Windows 8.  Based on the work of multiple
     developers including Matthew Garrett, Chun-Yi Lee, Seth Forshee,
     and Aaron Lu.

   - Fix from Aaron Lu makes the kernel follow Windows 8 by informing
     the firmware through the _DOS method that it should not carry out
     automatic brightness changes, so that brightness can be controlled
     by GUI"

* tag 'acpi-video-3.11' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
  ACPI / video: no automatic brightness changes by win8-compatible firmware
  ACPI / video / i915: No ACPI backlight if firmware expects Windows 8
  ACPI / video: Always call acpi_video_init_brightness() on init
  ACPICA: expose OSI version