Arch Linux

Mr. Alex

Member

Registered: 2010-08-26

Posts: 623

Can't adjust brightness on Toshiba A100

I was searching this forum for a solution but nothing I found works. I need to reduce brightness of Toshiba Satellite A100, the screen is too bright. Gnome on Arch, intel video drivers. I tried
https://bbs.archlinux.org/viewtopic.php?id=34107
https://bbs.archlinux.org/viewtopic.php?pid=281723

and several more.

Fn buttons don't work.
"echo NNN > /proc/acpi/video/XXX/XXX/brightness" doesn't make any change.
Gnome power manager doesn't affect anything...
Brightness applet does nothing.
xbacklight is not even in repos...

Please help.

lagagnon

Member

From: an Island in the Pacific...

Registered: 2009-12-10

Posts: 1,087

Website

Re: Can't adjust brightness on Toshiba A100

xbacklight works for me on a Toshiba L300. It is known as xorg-xbacklight and its in the extras repository.

To search a package use "pacman -Ss regex", e.g. "pacman -Ss xbacklight" will find it for you.

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Philosophy is looking for a black cat in a dark room. Metaphysics is looking for a black cat in a dark room that isn't there. Religion is looking for a black cat in a dark room that isn't there and shouting "I found it!". Science is looking for a black cat in a dark room with a flashlight.

Mr. Alex

Member

Registered: 2010-08-26

Posts: 623

Re: Can't adjust brightness on Toshiba A100

So it was already installed on my system.
I did

xbacklight = 60

it made a pause like doing something and nothing changed.
On the tty1 there is an error message after system booting is complete:

Cannot open display: default display

Maybe this is part of the reason?

caligo

Member

From: Stockholm

Registered: 2010-01-10

Posts: 79

Re: Can't adjust brightness on Toshiba A100

Have you tried adding "acpi_backlight=vendor" in your grub settings?

If that does not work, you could always try the setpci command -- on my Lenovo S10-3, I use this setpci script (and some custom keybindings to send the "up" and "down" commands to it):

#!/bin/bash
# increase/decrease/set/get the backlight brightness (range 0-255)
#
 
# PCI device on which to operate
DEVICE=00:02.0

# Amount to raise/lower the backlight when called with "up" or "down"
AMOUNT=8

# Minimum backlight value reachable via "down"
MIN=1

# Default backlight level when toggling on
DEFAULT=64
 
#get current brightness in hex and convert to decimal
var1=`setpci -s $DEVICE F4.B`
var1d=$((0x$var1))
case "$1" in
       up)
               #calculate new brightness
               var2=`echo "ibase=10; obase=16; a=($var1d+$AMOUNT);if (a<255) print a else print 255" | bc`
               echo "$0: increasing brightness from 0x$var1 to 0x$var2"
               setpci -s $DEVICE F4.B=$var2
               ;;
       down)
               #calculate new brightness
               var2=`echo "ibase=10; obase=16; a=($var1d-$AMOUNT);if (a>$MIN) print a else print $MIN" | bc`
               echo "$0: decreasing brightness from 0x$var1 to 0x$var2"
               setpci -s $DEVICE F4.B=$var2
               ;;
       set)
               #n.b. this does allow "set 0" i.e. backlight off
               echo "$0: setting brightness to 0x$2"
               setpci -s $DEVICE F4.B=$2
               ;;
       get)
               echo "$0: current brightness is 0x$var1"
               ;;
       toggle)
               if [ $var1d -eq 0 ] ; then
                       echo "toggling up"
                       setpci -s $DEVICE F4.B=$DEFAULT
               else
                       echo "toggling down"
                       setpci -s $DEVICE F4.B=0
               fi
               ;;
       *)
               echo "usage: $0 {up|down|set <val>|get|toggle}"
               ;;
esac
exit 0

I did not write this bash script, so I take absolutely no credit for it. However, I no longer remeber where I found it... There are many similar ones floating around various forums, though.

Mr. Alex

Member

Registered: 2010-08-26

Posts: 623

Re: Can't adjust brightness on Toshiba A100

What should "vendor" be on Toshiba A100?

skunktrader

Member

From: Brisbane, Australia

Registered: 2010-02-14

Posts: 1,543

Re: Can't adjust brightness on Toshiba A100

http://www.mjmwired.net/kernel/Document … meters.txt
Look at lines 167 and 168 for the valid values

Mr. Alex

Member

Registered: 2010-08-26

Posts: 623

Re: Can't adjust brightness on Toshiba A100

I should add this to
"kernel /vmlinuz26 root=/dev/sda2 ro vga=792" ?

caligo

Member

From: Stockholm

Registered: 2010-01-10

Posts: 79

Re: Can't adjust brightness on Toshiba A100

I should add this to
"kernel /vmlinuz26 root=/dev/sda2 ro vga=792" ?

Yes, just write it at the end of that line (e.g. "kernel /vmlinuz26 root=/dev/sda2 ro vga=792 acpi_backlight=vendor".

Mr. Alex

Member

Registered: 2010-08-26

Posts: 623

Re: Can't adjust brightness on Toshiba A100

I did it, rebooted and now it says:

xbacklight = 60
No outputs have backlight property

With root it says the same.

lagagnon

Member

From: an Island in the Pacific...

Registered: 2009-12-10

Posts: 1,087

Website

Re: Can't adjust brightness on Toshiba A100

That means xbacklight will not function with that display of yours. You will have to try this method:
https://bbs.archlinux.org/viewtopic.php?id=74914

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Philosophy is looking for a black cat in a dark room. Metaphysics is looking for a black cat in a dark room that isn't there. Religion is looking for a black cat in a dark room that isn't there and shouting "I found it!". Science is looking for a black cat in a dark room with a flashlight.