https://bugzilla.kernel.org/show_bug.cgi?id=43148
--- Comment #25 from Lee, Chun-Yi <j...@novell.com> 2012-09-03 01:59:48 ---
(In reply to comment #24)
> Today I had a bit time to try a view things on this Laptop.
>
> Here are my results.
>
> If I append acpi_backlight=vendor the folder in /sys/class/backlight
> disappears.
>
> I've updated the kernel to "linux-3.5.2" from the gentoo repository but this
> doesn't make a change.
>
> The FN + Cursor keys change the value form
> /sys/class/backlight/acpi_video0/backlight but both (echo value > device / and
> FN Cursor) doesn't affect the brightness.
>
> The graphic card is a Nvida card. Is the CONFIG_AGP_INTEL only for Intel
> Cards?
> or is this for the chipset witch controls the backlight.
Sorry for I didn't aware your video chip is Nvidia.
In your _BCM, it write brightness level value to EC register BLVL:
OperationRegion (ERAM, SystemMemory, 0xFF808201, 0x0100)
Field (ERAM, ByteAcc, NoLock, Preserve)
{
...
BLVL, 8, /* 0x51 */
Please help to check this value is really write to register.
Please run this acer_ec.pl from Carlos:
http://code.google.com/p/aceracpi/wiki/EmbeddedController
http://aceracpi.googlecode.com/svn/trunk/acer_ec/acer_ec.pl
Simple use:
watch -n 1 perl acer_ec.pl regs
Then, please write value to /sys/class/backlight/acpi_video0/backlight and
monitor the value changed on 0x51 register.
If the value is really changed, then the problem is in EC firmware, it didn't
really change backlight and causes a broken _BCM.
If _BCM broken, then the only way to control the backlight is opensource drm
driver (I think nouvea) need support this VGA chip.
But, per your 'lspci -vvv' result, I didn't see any kernel driver supported
your Nvidia 0df0 device. For nouvea support, that will be better report to
nouvea maintainer.
Are you using vesa driver now? or have any drm driver works on your machine?
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