tree adb84d398f5c3e3b2e0b24c46672f5dfc91da862
parent 34f8f1031cdccc73ab002dfe5f65ec89c3314457
author Aaron Lu <aaron.lu@intel.com> 1366632512 +0200
committer Rafael J. Wysocki <rafael.j.wysocki@intel.com> 1366632512 +0200

acpi: video: enhance the quirk detect logic of _BQC

Currently we decide if the _BQC is using index by first setting the
level to maximum, and then check if _BQC returned maximum; if not, we
say it is using index.

This is not true for some buggy systems, where the _BQC method will
always return a constant value(e.g. 0 or 100 for the two broken system)
and thus break the current logic. So this patch tries to enhance the
quirk detect logic for _BQC: we do this by picking a test_level, it can
be the maximum level or the mininum one based on some condition. And we
don't make the assumption that if _BQC returned a value that is not what
we just set, it must be using an index. Instead, we will compare the
value returned from _BQC and if it doesn't match, see if the returned
value is an index. And if still no, clear the capability of _BQC.

References: https://bugzilla.kernel.org/show_bug.cgi?id=42861
References: https://bugzilla.kernel.org/show_bug.cgi?id=56011
Reported-and-tested-by: Artem Savkov <artem.savkov@gmail.com>
Reported-by: Luis Medinas <lmedinas@gmail.com>
Reported-by: Cheppes <cheppes@mailinator.com>
Signed-off-by: Aaron Lu <aaron.lu@intel.com>
Acked-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>