i915: Fix opregion notifications

opregion-based platforms will send ACPI video event 0x80 for a range of
notification types for legacy compatibility. This is interpreted as a
display switch event, which may not be appropriate in the circumstances.
When we receive such an event we should make sure that the platform is
genuinely requesting a display switch before passing that event through
to userspace.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Tested-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Keith Packard <keithp@keithp.com>
diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
index db39e9e..ada4b4d 100644
--- a/drivers/acpi/video.c
+++ b/drivers/acpi/video.c
@@ -46,7 +46,6 @@
 
 #define PREFIX "ACPI: "
 
-#define ACPI_VIDEO_CLASS		"video"
 #define ACPI_VIDEO_BUS_NAME		"Video Bus"
 #define ACPI_VIDEO_DEVICE_NAME		"Video Device"
 #define ACPI_VIDEO_NOTIFY_SWITCH	0x80
@@ -1445,7 +1444,8 @@
 	case ACPI_VIDEO_NOTIFY_SWITCH:	/* User requested a switch,
 					 * most likely via hotkey. */
 		acpi_bus_generate_proc_event(device, event, 0);
-		keycode = KEY_SWITCHVIDEOMODE;
+		if (!acpi_notifier_call_chain(device, event, 0))
+			keycode = KEY_SWITCHVIDEOMODE;
 		break;
 
 	case ACPI_VIDEO_NOTIFY_PROBE:	/* User plugged in or removed a video
@@ -1475,7 +1475,8 @@
 		break;
 	}
 
-	acpi_notifier_call_chain(device, event, 0);
+	if (event != ACPI_VIDEO_NOTIFY_SWITCH)
+		acpi_notifier_call_chain(device, event, 0);
 
 	if (keycode) {
 		input_report_key(input, keycode, 1);