[ltp] Brightness control on X60

[Alex Deucher]

On 5/23/07, Nathaniel Smith <njs@pobox.com> wrote:
> On my X60 (brand new, 1709CTO, Intel video), I seem to have most
> things working under Debian but... for some reason the lcd brightness
> controls are broken.  (And here I thought my problem would be getting
> suspend working...)
>
> In particular, if I do Fn-Home/Fn-End to increase/decrease the
> brightness then it works fine in the console, but if I do it in X,
> then the backlight immediately turns off.  If I switch VTs back to the
> console, then the light turns back on, but if I switch back to X
> again, it turns off again.  (I.e., X is just dead, consistently and
> permanently, even though other things works fine.)  If I restart X
> (e.g., Ctrl-Alt-Backspace), that also brings things back, but rather
> defeats the purpose of all that suspend magic...
>
> I'm using the latest hal from Debian unstable (0.5.9), which
> supposedly knows that the magic buttons are handled directly in
> firmware (lshal says "laptop_panel.brightness_in_hardware = true"),
> and if I shut down hal etc. then the buttons still kill X, so I don't
> think it's misconfiguration there.
>
> In fact, if I use /proc/acpi/ibm/brightness or
> /sys/panel/backlight/*/brightness to adjust the backlight, it works
> perfectly -- doesn't affect X at all.  So a workaround would be to
> bind some other keys to control brightness in software, and just be
> careful to never touch the Fn-control keys.  However, this both bugs
> my sense of elegance, and also I'm uncomfortable with having "kill my
> computer" buttons sitting right there, even if I also know not to
> press them...
>
> Anyone else encountered anything like this?  Any ideas?

The new Xorg Intel driver (2.0 or higher) provides direct control of
the back light via an xrandr output property.  Perhaps the bios is
doing something the driver doesn't like.

Alex