[ltp] Command to dim the LCD brightness

[Alex Deucher]

On Wed, 12 Jan 2005 10:00:28 +0100, Bob Alexander <bob@ngi.it> wrote:
> Andr=E9 Wyrwa wrote:
> > Hi,
> >
> >
> >>could you be more specific in how could I use ACPI to lower brightness
> >>(not turn off) of my LCD ?? It must be possible since the Fn-Home and
> >>Fn-End thinkpad keys do that ....
> >
> >
> > The Fn-Home/End keys are interacting with the BIOS, bypassing ACPI.
> >
> > See Documentation/power/video_extension.txt in your kernel source tree =
for the new ACPI video interface.
> >
> > Andr=E9.
> >=20
> Andre',
> as usual you are extremely knowledgeable and helpful. That is exactly
> what I would need.
>=20
> In my 2.6.10 kernel the ACPI video extension is flagged as a module like
> all others but the video module does not appear to be loaded. I can load
> it manually and the /proc/acpi/video tree appears.
>=20
> Now the questions:
>=20
> 1) The /proc/acpi/video tree shows a single VID subdirectory and that sho=
ws:
> t40:/proc/acpi/video/VID# ls -l
> total 0
> dr-xr-xr-x  2 root root 0 2005-01-12 09:53 CRT0
> -r--r--r--  1 root root 0 2005-01-12 09:53 DOS
> dr-xr-xr-x  2 root root 0 2005-01-12 09:53 DVI0
> -r--r--r--  1 root root 0 2005-01-12 09:53 info
> dr-xr-xr-x  2 root root 0 2005-01-12 09:53 LCD0
> -r--r--r--  1 root root 0 2005-01-12 09:53 POST
> -r--r--r--  1 root root 0 2005-01-12 09:53 POST_info
> -r--r--r--  1 root root 0 2005-01-12 09:53 ROM
> dr-xr-xr-x  2 root root 0 2005-01-12 09:53 TV0
>=20
> The LCD0 subdir shows:
> t40:/proc/acpi/video/VID/LCD0# ls -l
> total 0
> -rw-r--r--  1 root root 0 2005-01-12 09:54 brightness
> -r--r--r--  1 root root 0 2005-01-12 09:54 EDID
> -r--r--r--  1 root root 0 2005-01-12 09:54 info
> -rw-r--r--  1 root root 0 2005-01-12 09:54 state
>=20
> and I was very excited but :( ->
> t40:/proc/acpi/video/VID/LCD0# cat brightness
> <not supported>
>=20
>  ...... seems I am out of luck ????
>=20
> Last question: I cannot find why in Debian other ACPI modules are
> automatically loaded but video was not ... ideas ?
>=20
> Anyway after loading it manually and attempting to echo a 0 into the
> brightness parameter here is what I find in dmesg ... see if you can
> gather some useful insight please.
>=20
> TIA
> Bob
>=20

Bob,

   You'll probably want to ask on the acpi devel list.  I've never
really used the features I just happened to read about them on LKML.

Alex