[PATCH v2 3/3] ACPI / video: Do not register backlight if win8 and native interface exists

Yves-Alexis Perez corsac at debian.org
Fri Sep 20 06:02:12 PDT 2013

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 at intel.com>
Tested-by: Yves-Alexis Perez <corsac at debian.org>
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