Backlight randomly switches to full brightness

impiaaa · 2014-01-13 06:04:15

Now, I'm not entirely new to Arch, but I have no idea how to diagnose this. While using my laptop with the backlight set to anything <100%, after a random interval of time independent of KB/mouse activity, the screen brightness will shoot back up to 100%. I'm running an Xfce4 DE, and the computer's a Lenovo W520. I've already determined that it isn't xscreensaver power management, because I've uninstalled it and killed it and the problem still persists. I've also eliminated Xfce power management since I told it not to dim the screen after any amount of time. I'm thinking at this point it may be some systemd or laptop-mode setting somewhere but I don't know where. Any help, advice, direction, or diagnostic procedures would be appreciated.

rebootl · 2014-01-13 17:15:47

You actually started debugging yourself, so why not continue.

From your post I get that you have laptop-mode(-tools) enabled(?).

Did you look at https://wiki.archlinux.org/index.php/La … brightness ?
It says for example "Note: Review the well-documented /etc/laptop-mode/conf.d/lcd-brightness.conf file for additional configuration details."

I don't use laptop-mode-tools myself, so I can't tell much more.

impiaaa · 2014-01-13 19:21:50

I looked at /etc/laptop-mode/conf.d/lcd-brightness.conf and I have CONTROL_BRIGHTNESS=0, so laptop-mode-tools shouldn't be affecting the brightness at all. In addition, ENABLE_LAPTOP_MODE_ON_AC=0, so even if laptop-mode was controlling brightness, it wouldn't while I'm plugged in (the problem still occurs when on AC).

ewaller · 2014-01-13 20:47:42

When the display is dimmed, unplug your power supply. Does it dim when changing to batteries? When you reconnect the power supply, does the brightness jump to 100% ?

Perhaps your laptop thinks it has changed over to battery, and then back to shore power. Might be a sign of dirty power or a flakey power supply.

impiaaa · 2014-01-14 07:02:56

No, the brightness does not change when I go to or from AC or battery power, nor is there a noticeable change in behavior.

Arch Linux

#1 2014-01-13 06:04:15

Backlight randomly switches to full brightness

#2 2014-01-13 17:15:47

Re: Backlight randomly switches to full brightness

#3 2014-01-13 19:21:50

Re: Backlight randomly switches to full brightness

#4 2014-01-13 20:47:42

Re: Backlight randomly switches to full brightness

#5 2014-01-14 07:02:56

Re: Backlight randomly switches to full brightness

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