ACPI video: Still use ACPI backlight control if _DOS doesn't exist
This fixes a regression in 3.4-rc1 caused by commit
ea9f8856bd6d4ed45885b06a338f7362cd6c60e5
(ACPI video: Harden video bus adding.)
Some platforms don't have _DOS control method, but the ACPI
backlight still works.
We should not invoke _DOS for these platforms.
https://bugzilla.kernel.org/show_bug.cgi?id=43168
Cc: Igor Murzov <intergalactic.anonymous@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
index 9577b6f..4134b30 100644
--- a/drivers/acpi/video.c
+++ b/drivers/acpi/video.c
@@ -558,6 +558,8 @@
union acpi_object arg0 = { ACPI_TYPE_INTEGER };
struct acpi_object_list args = { 1, &arg0 };
+ if (!video->cap._DOS)
+ return 0;
if (bios_flag < 0 || bios_flag > 3 || lcd_flag < 0 || lcd_flag > 1)
return -EINVAL;