[arch-general] Nvidia backlight control - acpi_video0/brightness changes - display doesn't?

[David C. Rankin]

On 11/18/2016 03:56 AM, Warp wrote:
> Do you use any special kernel boot parameters?
> 
> Using "acpi_backlight=vendor" helped me in a similar situation, though it
> was about another option interfering with backlight control.
> 
> Sylvain

Thanks Sylvain,

  I've tried with both "acpi_backlight=vendor" and "acpi_backlight=none", has
no effect on backlight (except to remove the sysfs acpi defaults). I've also
tried with xbacklight (and corrected the divide by zero in the script
recommended on the Backlight wiki page)

https://wiki.archlinux.org/index.php/Backlight#sysfs_modified_but_no_brightness_change

  xbacklight -get  (reports nothing)

So I really can't expect the -set option to set anything, frustrating... When
I use the backlight keys, the 'brightness' and 'actual_brightness' values go
up/down as it should AND the little screen indicator showing the level pops up
and shows the current and correct level, but the display brightness never changes.

I've got to get something figured out. This laptop will absolutely blind you
when you open a browser, or anything with a white background. I have the
backlight set at 40% in win10 and that works well. Here it looks like it is on
MAX continually. I will keep at it. If anyone has any other idea, let me know.
Thanks.

-- 
David C. Rankin, J.D.,P.E.