ACPI / video: update the skip case for acpi_video_device_in_dod()

If the firmware has declared more than 8 video output devices, and the
one that control the internal panel's backlight is listed after the
first 8 output devices, the _DOD will not include it due to the current
i915 operation region implementation. As a result, we will not create a
backlight device for it while we should. Solve this problem by special
case the firmware that has 8+ output devices in that if we see such a
firmware, we do not test if the device is in _DOD list. The creation of
the backlight device will also enable the firmware to emit events on
backlight hotkey press when the acpi_osi= cmdline option is specified on
those affected ASUS laptops.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=70241
Reported-and-tested-by: Oleksij Rempel <linux@rempel-privat.de>
Reported-and-tested-by: Dmitry Tunin <hanipouspilot@gmail.com>
Reported-and-tested-by: Jimbo <jaime.91@hotmail.es>
Cc: 3.18+ <stable@vger.kernel.org> # 3.18+
Signed-off-by: Aaron Lu <aaron.lu@intel.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 8 insertions, 2 deletions

diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
index 185a57d13723..1eaadff2e198 100644
--- a/drivers/acpi/video.c
+++ b/drivers/acpi/video.c
@@ -155,6 +155,7 @@ struct acpi_video_bus {
         u8 dos_setting;
         struct acpi_video_enumerated_device *attached_array;
         u8 attached_count;
+        u8 child_count;
         struct acpi_video_bus_cap cap;
         struct acpi_video_bus_flags flags;
         struct list_head video_device_list;
@@ -1159,8 +1160,12 @@ static bool acpi_video_device_in_dod(struct acpi_video_device *device)
         struct acpi_video_bus *video = device->video;
         int i;
 
-        /* If we have a broken _DOD, no need to test */
-        if (!video->attached_count)
+        /*
+         * If we have a broken _DOD or we have more than 8 output devices
+         * under the graphics controller node that we can't proper deal with
+         * in the operation region code currently, no need to test.
+         */
+        if (!video->attached_count || video->child_count > 8)
                 return true;
 
         for (i = 0; i < video->attached_count; i++) {
@@ -1413,6 +1418,7 @@ acpi_video_bus_get_devices(struct acpi_video_bus *video,
                         dev_err(&dev->dev, "Can't attach device\n");
                         break;
                 }
+                video->child_count++;
         }
         return status;
 }