===================================================================
@@ -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;
_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@intel.com> --- drivers/acpi/video.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html