ACPI: video: Prefer native over vendor
authorHans de Goede <hdegoede@redhat.com>
Mon, 14 Nov 2022 14:44:59 +0000 (15:44 +0100)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Sat, 7 Jan 2023 10:11:42 +0000 (11:11 +0100)
commit8af3d02aae3ecc23ee84d7078d1ebb3df7557dda
treefa8373b68a4a1f37980a8a68c21daeb96cebbe0c
parent923c1922bdbe44bdbebe57b5b976d40f68853653
ACPI: video: Prefer native over vendor

[ Upstream commit fb1836c91317e0770950260dfa91eb9b2170cb27 ]

When available prefer native backlight control over vendor backlight
control.

Testing has shown that there are quite a few laptop models which rely
on native backlight control (they don't have ACPI video bus backlight
control) and on which acpi_osi_is_win8() returns false.

Currently __acpi_video_get_backlight_type() returns vendor on these
laptops, leading to an empty /sys/class/backlight.

As a workaround for this acpi_video_backlight_use_native() has been
temporarily changed to always return true.

This re-introduces the problem of having multiple backlight
devices under /sys/class/backlight for a single panel.

Change __acpi_video_get_backlight_type() to prefer native over vendor
when available. So that it returns native on these models.

And change acpi_video_backlight_use_native() back to only return
true when __acpi_video_get_backlight_type() returns native.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
drivers/acpi/video_detect.c