[ Upstream commit 4f7f9645 ]

Some machines change the brightness themselves when a brightness hotkey
gets pressed, despite us telling them not to. This causes the brightness to
go two steps up / down when the hotkey is pressed. This is esp. a problem
on older machines with only a few brightness levels.

This commit adds a new hw_changes_brightness quirk which makes
acpi_video_device_notify() only call backlight_force_update(...,
BACKLIGHT_UPDATE_HOTKEY) and not do anything else, notifying userspace
that the brightness was changed and leaving it at that fixing the dual
step problem.

BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=204077Reported-by: Kacper Piwiński <cosiekvfj@o2.pl>
Tested-by: Kacper Piwiński <cosiekvfj@o2.pl>
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>