On Tuesday, July 16, 2013 11:24:05 AM Aaron Lu wrote: > On 07/15/2013 07:42 PM, Rafael J. Wysocki wrote: > > On Monday, July 15, 2013 10:36:15 AM Aaron Lu wrote: > >> On 07/13/2013 08:46 AM, Rafael J. Wysocki wrote: > >>> From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> > >>> > >>> 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_with_quirks(), that 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_with_quirks() instead of > >>> acpi_video_register() in i915_driver_load(). > >>> > >>> This change is based on earlier patches from Matthew Garrett, > >>> Chun-Yi Lee and Seth Forshee and Aaron Lu's comments. > >>> > >>> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> > >> > >> Reviewed-by: Aaron Lu <aaron.lu@xxxxxxxxx> > >> > >> BTW, I also tested on a Toshiba laptop Z830 where its AML code > >> claims support of win8, the result is as expected: ACPI video > >> interface is removed, i915 Xorg driver picks intel_backlight. > >> > >> Thanks for the fix. > > > > Cool, thanks for testing this! > > > > Can you please also ask bug reporters in the BZ entires related to this to test > > it too? > > Sure. > > To be clear, I actually tested the patch in your linux-next branch, > which turned out to be a little different in that you have fixed the > problem Igor raised here. > > I'll ask reporters to test on a stable tree with the following two > patches on top: > https://patchwork.kernel.org/patch/2812951/ (expose OSI version) > https://patchwork.kernel.org/patch/2827793/ (your updated patch) > or your linux-next branch, whichever they like. OK Thanks, Rafael _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
