On Mon, 2013-09-09 at 16:42 +0800, Aaron Lu wrote: > According to Matthew Garrett, "Windows 8 leaves backlight control up > to individual graphics drivers rather than making ACPI calls itself. > There's plenty of evidence to suggest that the Intel driver for > Windows [8] doesn't use the ACPI interface, including the fact that > it's broken on a bunch of machines when the OS claims to support > Windows 8. The simplest thing to do appears to be to disable the > ACPI backlight interface on these systems". > > There's a problem with that approach, however, because simply > avoiding to register the ACPI backlight interface if the firmware > calls _OSI for Windows 8 may not work in the following situations: > (1) The ACPI backlight interface actually works on the given system > and the i915 driver is not loaded (e.g. another graphics driver > is used). > (2) The ACPI backlight interface doesn't work on the given system, > but there is a vendor platform driver that will register its > own, equally broken, backlight interface if not prevented from > doing so by the ACPI subsystem. > Therefore we need to allow the ACPI backlight interface to be > registered until the i915 driver is loaded which then will unregister > it if the firmware has called _OSI for Windows 8 (or will register > the ACPI video driver without backlight support if not already > present). > > For this reason, introduce an alternative function for registering > ACPI video, __acpi_video_register(bool), that if ture is passed, > will check whether or not the ACPI video driver has already been > registered and whether or not the backlight Windows 8 quirk has to > be applied. If the quirk has to be applied, it will block the ACPI > backlight support and either unregister the backlight interface if > the ACPI video driver has already been registered, or register the > ACPI video driver without the backlight interface otherwise. Make > the i915 driver use __acpi_video_register() instead of > acpi_video_register() in i915_driver_load(), and the param passed > there is controlled by the i915 module level parameter > i915_take_over_backlight, which is set to false by default. > > This change is evolved from earlier patches of Matthew Garrett, > Chun-Yi Lee and Seth Forshee and is heavily based on two patches > from Rafael: > https://lkml.org/lkml/2013/7/17/720 > https://lkml.org/lkml/2013/7/24/806 > > Signed-off-by: Aaron Lu <aaron.lu@xxxxxxxxx> Tested-by: Igor Gnatenko <i.gnatenko.brain@xxxxxxxxx> > --- > drivers/acpi/internal.h | 2 ++ > drivers/acpi/video.c | 24 ++++++++++++++++-------- > drivers/acpi/video_detect.c | 15 ++++++++++++++- > drivers/gpu/drm/i915/i915_dma.c | 2 +- > drivers/gpu/drm/i915/i915_drv.c | 5 +++++ > drivers/gpu/drm/i915/i915_drv.h | 1 + > include/acpi/video.h | 9 +++++++-- > include/linux/acpi.h | 1 + > 8 files changed, 47 insertions(+), 12 deletions(-) -- Igor Gnatenko Fedora release 20 (Heisenbug) Linux 3.11.0-3.fc20.x86_64 -- Igor Gnatenko Fedora release 20 (Heisenbug) Linux 3.11.0-1.fc20.x86_64 -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
