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(-)