_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/show_bug.cgi?id=13955 Signed-off-by: Zhang Rui <rui.zhang@xxxxxxxxx> --- drivers/acpi/video.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) Index: linux-2.6/drivers/acpi/video.c =================================================================== --- linux-2.6.orig/drivers/acpi/video.c +++ linux-2.6/drivers/acpi/video.c @@ -870,7 +870,7 @@ acpi_video_init_brightness(struct acpi_v 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; @@ -892,15 +892,25 @@ acpi_video_init_brightness(struct acpi_v 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; -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
