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Commit 90c53ca4 authored by Zhang Rui's avatar Zhang Rui Committed by Len Brown
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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: default avatarZhang Rui <rui.zhang@intel.com>
Signed-off-by: default avatarLen Brown <len.brown@intel.com>
parent 4a703a8f

drivers/acpi/video.c

+14 −4
Original line number Diff line number Diff line
@@ -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;