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authorAaron Lu <aaron.lu@intel.com>2013-07-16 13:08:05 +0800
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2013-07-18 02:08:16 +0200
commitefaa14c7e981bdf8d3c8d39d3ed12bdc60faabb8 (patch)
treee393015f17feca2feec73e1a43d50967c4eb6b73 /drivers
parent8c5bd7adb2ce47e6aa39d17b2375f69b0c0aa255 (diff)
ACPI / video: no automatic brightness changes by win8-compatible firmware
Starting from win8, MS backlight control driver will set bit 2 of the parameter of control method _DOS, to inform firmware it should not perform any automatic brightness changes. This mostly affects hotkey notification deliver - if we do not set this bit, on hotkey press, firmware may choose to adjust brightness level instead of sending out notification and doing nothing. So this patch sets bit 2 when calling _DOS so that GUIs can show the notification window on hotkey press. This behavior change is only necessary for win8 systems. The MS document on win8 backlight control is here: http://msdn.microsoft.com/en-US/library/windows/hardware/jj159305 References: https://bugzilla.kernel.org/show_bug.cgi?id=52951 References: https://bugzilla.kernel.org/show_bug.cgi?id=56711 Reported-by: Micael Dias <kam1kaz3@gmail.com> Reported-by: Dan Garton <dan.garton@gmail.com> Reported-by: Bob Ziuchkovski <bob.ziuchkovski@gmail.com> Signed-off-by: Aaron Lu <aaron.lu@intel.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/acpi/video.c10
1 files changed, 8 insertions, 2 deletions
diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
index e9d4bb60c35c..c9fa4621ed25 100644
--- a/drivers/acpi/video.c
+++ b/drivers/acpi/video.c
@@ -1539,14 +1539,20 @@ static int acpi_video_bus_put_devices(struct acpi_video_bus *video)
/* acpi_video interface */
+/*
+ * Win8 requires setting bit2 of _DOS to let firmware know it shouldn't
+ * preform any automatic brightness change on receiving a notification.
+ */
static int acpi_video_bus_start_devices(struct acpi_video_bus *video)
{
- return acpi_video_bus_DOS(video, 0, 0);
+ return acpi_video_bus_DOS(video, 0,
+ acpi_video_backlight_quirks() ? 1 : 0);
}
static int acpi_video_bus_stop_devices(struct acpi_video_bus *video)
{
- return acpi_video_bus_DOS(video, 0, 1);
+ return acpi_video_bus_DOS(video, 0,
+ acpi_video_backlight_quirks() ? 0 : 1);
}
static void acpi_video_bus_notify(struct acpi_device *device, u32 event)