Samsung laptop screen brightness control?

erik2282 · 08-21-2012, 02:53 AM

Samsung R480
Linux Mint 13 KDE

The Fn keys for the brightness do not work. I am using this workaround:
sudo setpci -s 00:02.0 F4.b=XX.
The XX is the level of brightness; 0 being the darkest, 100 brightest. I normally have it at 25. If I reboot or sleep the laptop, it will go to a default level, not sure what the number is but its very bright and hurts my eyes after just a little bit.

How do I get the Fn keys to work or at least how do I get the value to stay at 25 by default??

I've been using Mint w/kde on this laptop since Mint 10 and have always had to do this workaround for the brightness.

Thanks.

business_kid · 08-21-2012, 04:03 AM

get a collection of acpi stuff from debian & fedora, as they both have good stuff. I got sorted on slackware by running acpid with -l (log to syslog)

Quote:

acpid -l

In one terminal I ran

Quote:

tail -f /var/log/messages

and then with that visible, I pressed the Fn buttons, and acpi logged the events. Then I put the event (as logged) in /etc/acpi/events,

Quote:

bash-4.1$ cat /etc/acpi/events/video_brightnessup
# /etc/acpi/events/video_brightnessup
event=video.* 00000086
action=/etc/acpi/video_brightnessup.sh

and the risked or copied/hacked a bit of a script in /etc/acpi

Quote:

bash-4.1$ cat /etc/acpi/video_brightnessup.sh
#!/bin/sh

BRIGHTNESS = { cat /sys/devices/virtual/backlight/acpi_video0/brightness}
BRIGHTNESS = [ $BRIGHTNESS + 1 ]
echo -n $BRIGHTNESS > /sys/devices/virtual/backlight/acpi_video0/brightness