[arch-general] Fn-F{5, 6} keys for backlight - how to disable native handling?

[Leonardo Dagnino]

2013/6/25 Oon-Ee Ng <ngoonee.talk at gmail.com>

> I have an ASUS N56V where the Fn-F{5,6} keys do not work natively (no
> output in xev when pressed). This is very easily worked-around using
> acpi_os="!Windows 2012".
>
> The resulting control is something along the 3-10 range (10 being
> brightest and 0 being off, these are not the actual numerical values),
> which means I can't dim my backlight beyond a certain value.
> Similarly, using xbacklight and setting to 0 actually gives a "3"
> backlight, not totally blank. Setting
> /sys/class/backlight/intel_backlight/brightness to 0 does turn the
> screen off though.
>
> The problem is that if I write a simple script to adjust brightness
> and bind that using xbindkeys, the native handler still works for a
> fraction of a second before the value I calculate takes effect. This
> results in a brief flicker everytime I press the keys.
>
> Conclusion - I want to disable this native handling of Fn-F{5,6}, is
> this possible or is this not software-controlled?
>


I have a similar problem on a Dell XPS L701x - however, works natively but
not work correctly, just setting the brightness from really bright to
not-so-bright (but still very visible). xbacklight works, and on it all
brightness levels are accessible.

I also have a flickering effect when I use acpid for the keyboard key to
call xbacklight.

I think this probably has something to do with Nvidia Optimus, since both
our systems have it (mine has a GT435M).

I can also change it manually from /sys; but I'm not sure from where since
I'm not with that system at the moment. I think it is from acpi_video0,
however I have both it and intel_backlight in /sys/class/backlight/. One
works, having a strange precision, going from 0 to ~6500 (not a round
number), and the other doesn't.

I noticed this also happens in Windows, but it is difficult to notice since
it is handled really fast.

-- 
Leonardo Dagnino