[SOLVED] How to make intel_backlight settings permanent

amaro · 09-30-2014, 09:40 PM

Hi guys!

I want to make this permanent

Code:

echo 123 > /sys/class/backlight/intel_backlight/brightness

How to do it?

Thank you!

yars · 09-30-2014, 11:47 PM

You can put this line in your /etc/rc.d/rc.local, but the DE may have own settings and override them.

amaro · 10-01-2014, 01:37 AM

Quote:

Originally Posted by yars

You can put this line in your /etc/rc.d/rc.local, but the DE may have own settings and override them.

Absolutely right. Having it in rc.local doesn't work. Something different has to be done.

EYo · 10-01-2014, 07:12 AM

Quote:

Originally Posted by amaro

I want to make this permanent

Code:

echo 123 > /sys/class/backlight/intel_backlight/brightness

A search revealed this timing issue solution for setting in rc.local:

Code:

(sleep 5; echo 123 > /sys/class/backlight/intel_backlight/brightness)&

Or man sysctl

I can set my backlight from the cli with

Code:

echo 2 > /sys/class/backlight/acpi_video0/brightness

/etc/sysctl.conf for permanent setting. Or maybe

Code:

xbacklight -set N

might also work from a DE autostart script, I did not test. HTH

If you do have success with the sysctl.conf, hope you can post back what works. Thanks.

solarfields · 10-01-2014, 08:49 AM

That's how I set xgamma and xbacklight:

no graphic log in
using GDM
using KDM

Note that KDE will remember your backlight settings.

amaro · 10-01-2014, 11:51 AM

@ solarfields
Nice! I didn't try it though. I used to use gamma in the past but now I prefer rc.local. Thank you!

@ EYo
Thank you for your suggestions!

Here is the solution:

Code:

sleep 10 && echo '123' > '/sys/class/backlight/intel_backlight/brightness' &

dunric · 10-01-2014, 07:14 PM

A little bit dirty solution, if you'd ask me. Better find out where the brightness get altered and avoid sleeping to work around race condition.

Insipred by Arch Linux wiki you may use an udev rule, by putting following line in /etc/udev/rules.d/81-backlight.rules

Code:

SUBSYSTEM=="backlight", ACTION=="add", KERNEL=="intel_backlight", ATTR{brightness}="123"

Written from top of my head, untested.

amaro · 10-02-2014, 12:35 AM

Quote:

Originally Posted by dunric

A little bit dirty solution, if you'd ask me. Better find out where the brightness get altered and avoid sleeping to work around race condition.
Insipred by Arch Linux wiki you may use an udev rule.

Sleeping is not something I prefer but it works. I decided to try the udev rule you mention and it didn't work. Here is an interesting read on that suggesting there is a bug in kernel 3.14.x (though I am using 3.10) with link to the Arch forum http://eatpeppershothot.blogspot.com...ht-bug-in.html,
If something more elegant come out I will give it a shot.
Thanks!

yars · 10-03-2014, 02:55 PM

I'm was the same problem, but I would like to have automatically saving and restoring the brightness. Reading this thread I'm found a solution:
1. To avoid sleeping I'm use a udev rule:

Code:

ACTION=="add", SUBSYSTEM=="backlight", KERNEL=="intel_backlight", RUN+="/etc/udev/brightness.sh restore"

2. To save a brightness state, I'm have a rc.local_shutdown with these lines:

Code:

if [ -x /etc/udev/brightness.sh ] ; then
    /etc/udev/brightness.sh store
fi

3. Here is a script that makes all the work:

Code:

#!/bin/sh

restore() {
    if [ -f /etc/brightness ]; then
	echo -n "Restoring previous brightness value... "
	cat /etc/brightness > /sys/class/backlight/intel_backlight/brightness && echo "Done."
    fi
}

store() {
    echo -n "Saving current brightness value to /etc/brightness... "
    cat /sys/class/backlight/intel_backlight/brightness > /etc/brightness && echo "Done."
}

case $1 in
      store) store;;
    restore) restore;;
          *) echo "Usage: $0 store | restore"
esac