ACPI: video: Loosen strictness of video bus detection code

BugLink: http://bugs.launchpad.net/bugs/333386

Currently a video bus device must (beside other criteria) define _DOD and
_DOS methods to be considered a video device.
Some broken BIOSes prevented working backlight control by only defining both
for one (non-existing bus) and only _DOD for the rest. With this patch in
place the other bus definitions were considered too and backlight control
started to work again.

Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 6 insertions, 1 deletions

diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
index f6e54bf8dd96..64e3c581b7a9 100644
--- a/drivers/acpi/video.c
+++ b/drivers/acpi/video.c
@@ -1109,7 +1109,12 @@ static int acpi_video_bus_check(struct acpi_video_bus *video)
          */
 
         /* Does this device support video switching? */
-        if (video->cap._DOS) {
+        if (video->cap._DOS || video->cap._DOD) {
+                if (!video->cap._DOS) {
+                        printk(KERN_WARNING FW_BUG
+                                "ACPI(%s) defines _DOD but not _DOS\n",
+                                acpi_device_bid(video->device));
+                }
                 video->flags.multihead = 1;
                 status = 0;
         }