diff options
| author | Zhang Rui <rui.zhang@intel.com> | 2009-08-31 12:39:54 -0400 |
|---|---|---|
| committer | Len Brown <len.brown@intel.com> | 2009-08-31 12:39:54 -0400 |
| commit | 90c53ca426cb93d15eefea79dcf6bd15ad3ffeb4 (patch) | |
| tree | 40ca4e3d2fd7a1b921abc9ced9af2fc78151a161 /drivers/acpi/video.c | |
| parent | 4a703a8fe562824f269943d995ddff35077253a9 (diff) | |
| download | lwn-90c53ca426cb93d15eefea79dcf6bd15ad3ffeb4.tar.gz lwn-90c53ca426cb93d15eefea79dcf6bd15ad3ffeb4.zip | |
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>
Diffstat (limited to 'drivers/acpi/video.c')
| -rw-r--r-- | drivers/acpi/video.c | 18 |
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; |