ACPI video: add a warning message if _BQC is not found

ACPI backlight control w/o _BQC support is kinda firmware bug.
Add a warning if _BQC is not implemented.

Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/acpi/video_detect.c b/drivers/acpi/video_detect.c
index 50e3d2dbf3af..09737275e25f 100644
--- a/drivers/acpi/video_detect.c
+++ b/drivers/acpi/video_detect.c
@@ -55,6 +55,9 @@ acpi_backlight_cap_match(acpi_handle handle, u32 level, void *context,
                 ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Found generic backlight "
                                   "support\n"));
                 *cap |= ACPI_VIDEO_BACKLIGHT;
+                if (ACPI_FAILURE(acpi_get_handle(handle, "_BQC", &h_dummy)))
+                        printk(KERN_WARNING FW_BUG PREFIX "ACPI brightness "
+                                        "control misses _BQC function\n");
                 /* We have backlight support, no need to scan further */
                 return AE_CTRL_TERMINATE;
         }