https://bugzilla.kernel.org/show_bug.cgi?id=43148
--- Comment #30 from Lee, Chun-Yi <j...@novell.com> 2012-09-04 03:14:18 ---
(In reply to comment #26)
> Hi,
>
> I've tested this with the acer_ec.pl File.
>
> Please find the following two files attached.
>
> Here is a detailed Report what I've done.
> 1. Installed the latest Nvidia driver for gentoo (Version: 304.43)
> (I had the proprietary drivers installed all the time)
> List of the loaded modules:
> Module Size Used by
> nvidia 11175245 41
> ehci_hcd 29013 0
> atl1c 26803 0
> 2. ran the perl script with the following command
> --> perl acer_ec.pl regs > before_change.txt
> 3. ran the echo command to change the brightness
> --> cd /sys/class/backlight/acpi_video0
> --> echo 3 > brightness
> 4. ran the perl script again with the following command
> --> perl acer_ec.pl regs > after_change_to_value_3.txt
>
Thanks for your testing result. It confirm the brightness value already wrote
to
EC register:
in before_change.txt:
01
__ __
50 | 0 9
in after_change_to_value_3.txt
01
__ __
50 | 0 3 <=== number changed to 3
So, this is EC firmware's problem, it didn't really change brightness level.
Obviously ODM didn't test the standard _BCM acpi method because windows 7
doesn't use it.
> The brightness of the screen didn't change at all.
>
> Do you think that this is a problem of the Nvidia Drivers or is it a problem
> of
> any other chipset of the mainboard. (Sorry for this question, but I'am not so
> firm with this details.)
This is a EC firmware problem, the responsibility should take by OEM/ODM. The
drm driver is a workaround we HOPE it can avoid brightness control problem.
If drm driver support your machine, it should generate brightness interface in
/sys/class/backlight/ folder, e.g. /sys/class/backlight/intel , then we can use
'acpi_backlight=vendor' to avoid user space application try to change
brightness through acpi interface.
So, if we want drm driver can help to workaround this issue, the driver should
support your machine with kernel backlight framework, or it supported backlight
control by video manufacturer's proprietary way.
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