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authorZhang Rui <rui.zhang@intel.com>2009-08-31 12:39:54 -0400
committerLen Brown <len.brown@intel.com>2009-08-31 12:39:54 -0400
commit90c53ca426cb93d15eefea79dcf6bd15ad3ffeb4 (patch)
tree40ca4e3d2fd7a1b921abc9ced9af2fc78151a161
parent4a703a8fe562824f269943d995ddff35077253a9 (diff)
ACPI video: work-around BIOS AML bug in _BQC
_BQC on some laptops returns an uninitialized value when it's invoked for the first time. Set the laptop to the maximum backlight level in this case. http://bugzilla.kernel.org/attachment.cgi?id=22675 Signed-off-by: Zhang Rui <rui.zhang@intel.com> Signed-off-by: Len Brown <len.brown@intel.com>
-rw-r--r--drivers/acpi/video.c18
1 files changed, 14 insertions, 4 deletions
diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
index a8432c291f40..097f24c87d82 100644
--- a/drivers/acpi/video.c
+++ b/drivers/acpi/video.c
@@ -878,7 +878,7 @@ acpi_video_init_brightness(struct acpi_video_device *device)
br->flags._BCM_use_index = br->flags._BCL_use_index;
/* _BQC uses INDEX while _BCL uses VALUE in some laptops */
- br->curr = level_old = max_level;
+ br->curr = level = max_level;
if (!device->cap._BQC)
goto set_level;
@@ -900,15 +900,25 @@ acpi_video_init_brightness(struct acpi_video_device *device)
br->flags._BQC_use_index = (level == max_level ? 0 : 1);
- if (!br->flags._BQC_use_index)
+ if (!br->flags._BQC_use_index) {
+ /*
+ * Set the backlight to the initial state.
+ * On some buggy laptops, _BQC returns an uninitialized value
+ * when invoked for the first time, i.e. level_old is invalid.
+ * set the backlight to max_level in this case
+ */
+ for (i = 2; i < br->count; i++)
+ if (level_old == br->levels[i])
+ level = level_old;
goto set_level;
+ }
if (br->flags._BCL_reversed)
level_old = (br->count - 1) - level_old;
- level_old = br->levels[level_old];
+ level = br->levels[level_old];
set_level:
- result = acpi_video_device_lcd_set_level(device, level_old);
+ result = acpi_video_device_lcd_set_level(device, level);
if (result)
goto out_free_levels;