Arch Linux

The_Air_Penguin

Member

Registered: 2008-12-04

Posts: 12

Backlight changing causes twitching

This problem appeared some time ago with a system update, before two months or so. Since it came with an update, I didn't try to fix it and hoped that some next update would fix the problem. However, the problem is still here and I would like to ask for help.

Here's what's wrong: screen backlight changing used to be inverted (I would go up when I turned it down). Then the update came and it wasn't inverted anymore, but now it's causing "twitching": whenever I change backlight, Xorg begins to take 20-35% of CPU and it lasts for some time ranging between a few seconds to a whole minute or so. Even though it says only 30%, it feels like a lot more: mouse begins acting almost chaotically, sound almost completely stops and everything is so slow that I even have to wait for letters to appear when I type on the keyboard.

I was wondering if someone else had any similar problems or if anyone has an idea on how to solve this. The computer is a Lenovo ThinkPad SL500 laptop.

Thanks.

The_Air_Penguin

Member

Registered: 2008-12-04

Posts: 12

Re: Backlight changing causes twitching

I would just like to say that it got worse today. It lasts longer now and it's making the whole screen go light-dark.

edubarr

Member

Registered: 2009-03-25

Posts: 19

Re: Backlight changing causes twitching

I remember having this problem with my T61. I solved it by creating of my own acpi event and action scrip to modify the brightness levels through procfs (it was always slow on sysfs).

Anyways, I don't know if I still have the scripts (AFAIK it started working with an update to hal/acpi a while ago) but you can find more information about it here: http://www.thinkwiki.org/wiki/LCD_Brightness

Have a look at this thread as well: http://bbs.archlinux.org/viewtopic.php?id=39076. I remembered I was having issues with 2 different acpi codes being sent for the same fn-key combo and had to disable one of them (the video one if I remember correctly).

Last edited by edubarr (2009-04-15 14:57:03)

Gather

Member

From: Poland, Konin

Registered: 2007-07-07

Posts: 8

Re: Backlight changing causes twitching

http://bugzilla.kernel.org/show_bug.cgi?id=12249#c109