[ltp] Command to dim the LCD brightness

[Tino Keitel]

On Thu, Jan 13, 2005 at 01:41:38 +0100, André Wyrwa wrote:
> Hi Bob,
> 
> > t40:/proc/acpi/video/VID/LCD0# cat brightness
> > <not supported>
> 
> yepp, same here.
> 
> > Last question: I cannot find why in Debian other ACPI modules are 
> > automatically loaded but video was not ... ideas ?
> 
> Not a debianiac ;-), but i guess it's because this module is new in
> 2.6.10 and so Debian doen't know about it.

ACPI modules which should be loaded can be written into
/etc/default/acpid.

> 
> There should be some file /etc/sysconfig/modules or something like that
> listing modules that are going to be loaded at startup. If you put a
> line for the video module in there it should be included at boot time.

In Debian, it's /etc/modules. There is also a tools called "modconf"
which lets you choos the modules and corresponding module parameters.

> 
> This probably means...ACPI display switching is possible, mutli-head is
> possible, no video rom found, no POST data found (don't really know
> anything about that). I guess that brightness is not supported because
> the rom is not found.
> 
> > Unable to handle kernel NULL pointer dereference at virtual address 00000004
> >   printing eip:
> > f8b388b1
> > *pde = 00000000
> > Oops: 0000 [#1]
> 
> Ooops, what's that? Might come from echoing 0
> into /proc/acpi/video/LCD0/brightness. Guess you shouldn't do it as long
> as it's not supported.

I doubt that the 0 from the echo would cause a NULL pointer
dereference. This would mean that the argument from the echo is going
to be used as a pointer, which is somewhat stupid. :-)

Regards,
Tino