[PATCH v4 0/4] Fix Win8 backlight issue

[Aaron Lu]

v4:
Remove decleration and stub for acpi_video_unregister_backlight in
video.h of patch 2/4 since that function doesn't exist anymore in v3.

v3:
1 Add a new patch 4/4 to fix some problems in thinkpad-acpi module;
2 Remove unnecessary function acpi_video_unregister_backlight introduced
  in patch 2/4 as pointed out by Jani Nikula.

v2:
v1 has the subject of "Rework ACPI video driver" and is posted here:
http://lkml.org/lkml/2013/9/9/74
Since the objective is really to fix Win8 backlight issues, I changed
the subject in this version, sorry about that.

This patchset has four patches, the first introduced a new API named
backlight_device_registered in backlight layer that can be used for
backlight interface provider module to check if a specific type backlight
interface has been registered, see changelog for patch 1/4 for details.
Then patch 2/4 does the cleanup to sepeate the backlight control and
event delivery functionality in the ACPI video module and patch 3/4
solves some Win8 backlight control problems by avoiding register ACPI
video's backlight interface if:
1 Kernel cmdline option acpi_backlight=video is not given;
2 This is a Win8 system;
3 Native backlight control interface exists.
Patch 4/4 fixes some problems in thinkpad-acpi module.

Technically, patch 2/4 is not required to fix the issue here. So if you
think it is not necessary, I can remove it from the series.

Aaron Lu (4):
  backlight: introduce backlight_device_registered
  ACPI / video: seperate backlight control and event interface
  ACPI / video: Do not register backlight if win8 and native interface
    exists
  thinkpad-acpi: fix handle locate for video and query of _BCL

 drivers/acpi/internal.h              |   5 +-
 drivers/acpi/video.c                 | 442 ++++++++++++++++++++---------------
 drivers/acpi/video_detect.c          |  14 +-
 drivers/platform/x86/thinkpad_acpi.c |  31 ++-
 drivers/video/backlight/backlight.c  |  31 +++
 include/linux/backlight.h            |   4 +
 6 files changed, 322 insertions(+), 205 deletions(-)

-- 
1.8.4.12.g2ea3df6