On mar., 2013-09-17 at 17:23 +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".
So for Win8 systems, if there is native backlight control interface registered by GPU driver, ACPI video will not register its own. For users who prefer to keep ACPI video's backlight interface, the existing kernel cmdline option acpi_backlight=video can be used.
This patch is an evolution from previous work done by Matthew Garrett, Chun-Yi Lee, Seth Forshee and Rafael J. Wysocki.
Signed-off-by: Aaron Lu aaron.lu@intel.com
Tested-by: Yves-Alexis Perez corsac@debian.org