Arch Linux

jacobr

Member

Registered: 2018-01-03

Posts: 1

Backlight issue, setpci at boot

Hi all,

After playing about with Ubuntu for a few months, I've decided to install Arch on my machine. I'm configuring my hardware settings, and have run into some trouble adjusting the backlight.

My setup:
MacBook Pro, 11,3
Nvidia graphics drivers

The issue:
The backlight is adjustable after running the command "# setpci -v -H1 -s 00:01.00 BRIDGE_CONTROL=0". The brightness is read from /sys/class/backlight/gmux_backlight/brightness, which is adjustable using the backlight +/- keys.

However, I cannot get this to stick. On Ubuntu I simply threw this command into rc.local to solve the problem.

Attempted solutions:
1. I've tried creating a new systemd service "apple-backlight" to run this command. When I run "systemctl start apple-backlight," things work beautifully. When I enable the service and reboot, however, the brightness is not adjustable.
2. I tried making a cron job to run the command at boot (@reboot). No luck.

What's strange is that when I pipe the output of the service or cron job to a log file, I can see that my service/cron job is returning the expected return value. However, the backlight is not adjustable until the command is run after boot.

How can I troubleshoot this? Any suggestions?

Thanks!

seth

Member

From: Won't reply 2 private help req

Registered: 2012-09-03

Posts: 78,500

Re: Backlight issue, setpci at boot

What does the service look like? I could imagine you need to run it after the graphical target?

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paysonwallach

Member

Registered: 2019-05-28

Posts: 2

Re: Backlight issue, setpci at boot

Not sure if you're still having the problem or not but I ran into this issue and managed to solve it with some help from this thread. My solution was to create a service that runs the mentioned command after graphical.target.

[Unit]
Description=Enable backlight control
Wants=graphical.target
After=graphical.target

[Service]
Type=simple
ExecStart=/usr/bin/setpci -v -H1 -s 00:01.00 BRIDGE_CONTROL=0

Last edited by paysonwallach (2019-05-28 18:32:21)