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laptop brightness is max after reboot [SOLVED]
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Efo
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Joined: 23 Jun 2005
Posts: 420

PostPosted: Sun Apr 02, 2017 4:32 pm    Post subject: laptop brightness is max after reboot [SOLVED] Reply with quote

Hi all,

I cant figure out how to set a default value for the backlight of my laptop. The controls work, but every time I reboot the light is set to max.

gentoo wiki mentions
Code:
/etc/laptop-mode/conf.d/lcd-brightness.conf
(which I think is where the default values are stored), but I dont have that file.

I guess what I am looking for is where to generate the conf file and then I will follow this syntax, but since I dont have the file that may be obsolete.

Any help is (as always) highly appreciated.

Thanks,

Efo


Last edited by Efo on Mon Apr 03, 2017 12:55 am; edited 1 time in total
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cboldt
l33t
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Joined: 24 Aug 2005
Posts: 839

PostPosted: Sun Apr 02, 2017 6:13 pm    Post subject: Reply with quote

I don't use the "laptop-mode-tools", which might include the "missing config file" that you ask about.

If you have installed laptop-mode-tools, and the config file still isn't there, you would just create it.

The method I use to set LCD brightness at boot is a one line command in /etc/local.d/local.start

That file is not part of any package, but is suggested by openrc. More particularly, it is suggested by a message in /etc/init.d/local. If you don't use openrc to start your system (that is, if you use systemd), then this one liner in /etc/local.d/local.start would have NO effect.

I made /etc/local.d/local.start with a text editor. After I created the file, I made sure /etc/init.d/local was part of my openrc startup sequence, by issuing the command `rc-update add local default`

Code:
# /etc/local.d/local.start:
# $Header: /home/cvsroot/gentoo-src/rc-scripts/etc/conf.d/local.start,v 1.4 2002/11/18 19:39:22

# This is a good place to load any misc.
# programs on startup ( 1>&2 )

# Adjust backlight brightness
echo 8 > /sys/class/backlight/acpi_video0/brightness


Your computer and setup may use a different "/sys" file for this function, but I see reference to this location in the config file that you reviewed.
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khayyam
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Joined: 07 Jun 2012
Posts: 6228
Location: Room 101

PostPosted: Mon Apr 03, 2017 12:48 am    Post subject: Reply with quote

Efo ... as cboldt mentions, its somewhat dependent on what your backlight provides, but here is a script that (absent of any parameter) will set the brightness to half that of max_brightness (you could of course set the default to whatever value you want).

Code:
#!/bin/sh
set -e

backlight_sys_dir="/sys/class/backlight/intel_backlight"

read -r max_brightness < "${backlight_sys_dir}/max_brightness"
read -r curr_brightness < "${backlight_sys_dir}/brightness"

if [ "$#" -eq 0 ] ; then
    # set to half that of 'max_brightness'
    echo $((max_brightness / 2)) > ${backlight_sys_dir}/brightness
    exit 0
fi

case "$1" in
      up) increment="+ 10" ;;
    down) increment="- 10" ;;
       *) exit 1 ;;
esac

new_brightness=$(($curr_brightness $increment))

if $((new_brightness < 1)) || $((new_brightness > $max_brightness)); then
    exit 1
else
    echo "$new_brightness" > ${backlight_sys_dir}/brightness
fi

This could similarly used in /etc/local.d ... and you can also then call the script and pass 'up' and 'down' to adjust the brightness by plus/minus 10 (I call it via acpid with those parameters taken from 'brightnessup' and 'brightnessdown' keys).

HTH & best ... khay
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Efo
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Joined: 23 Jun 2005
Posts: 420

PostPosted: Mon Apr 03, 2017 12:54 am    Post subject: Reply with quote

Hi cboldt and khayyam,

Thank you for the reply.
For some reason I was expecting to have some config file already present; however, your suggestions make a lot of sense: just a little scripting will do.

Thank you for your help.

Cheers,

Efo
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