ACPI / video: no automatic brightness changes by win8-compatible firmware

Aaron Lu · rafaeljw · commit efaa14c7e981 · 2013-07-18T02:08:16.000+02:00
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>
diff --git 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)

Original file line number	Diff line number	Diff line change
`@@ -1539,14 +1539,20 @@ static int acpi_video_bus_put_devices(struct acpi_video_bus *video)`
`1539`	`1539`
`1540`	`1540`	`/* acpi_video interface */`
`1541`	`1541`
	`1542`	`+/*`
	`1543`	`+ * Win8 requires setting bit2 of _DOS to let firmware know it shouldn't`
	`1544`	`+ * preform any automatic brightness change on receiving a notification.`
	`1545`	`+ */`
`1542`	`1546`	`static int acpi_video_bus_start_devices(struct acpi_video_bus *video)`
`1543`	`1547`	`{`
`1544`		`- return acpi_video_bus_DOS(video, 0, 0);`
	`1548`	`+ return acpi_video_bus_DOS(video, 0,`
	`1549`	`+ acpi_video_backlight_quirks() ? 1 : 0);`
`1545`	`1550`	`}`
`1546`	`1551`
`1547`	`1552`	`static int acpi_video_bus_stop_devices(struct acpi_video_bus *video)`
`1548`	`1553`	`{`
`1549`		`- return acpi_video_bus_DOS(video, 0, 1);`
	`1554`	`+ return acpi_video_bus_DOS(video, 0,`
	`1555`	`+ acpi_video_backlight_quirks() ? 0 : 1);`
`1550`	`1556`	`}`
`1551`	`1557`
`1552`	`1558`	`static void acpi_video_bus_notify(struct acpi_device *device, u32 event)`