View Full Version : [SOLVED] Change in LED control steps after login Thinkpad X220

January 15th, 2012, 12:41 AM

my system is showing the following odd behaviour

At login screen using the LED brightness keys gives 16 levels min to max as described in thinkpad_acpi.txt http://www.mjmwired.net/kernel/Documentation/laptops/thinkpad-acpi.txt. (http://www.mjmwired.net/kernel/Documentation/laptops/thinkpad-acpi.txt)

After login I now only have 6 levels available.

Any ideas??

Thinkpad X220 i5, Ubuntu 11.10 (x64), Unity interface

January 29th, 2012, 05:18 AM
Looking in to this a bit more it seems that it is the mapping of the keys themselves. Using

"/sys/class/backlight/acpi_video0/device/backlight/acpi_video0$ more actual_brightness"

in terminal reveals that each key press increases/decreases brightness by 3 steps. So the actual range is 0-15.

Anyone know if this is Lenovo specific or a general ubuntu/unity issue?

January 29th, 2012, 06:30 AM
So I have resolved this by using the troubleshooting guide https://wiki.ubuntu.com/Kernel/Debugging/Backlight :)

Basically I needed to add the boot options to enable the vendor acpi mode and get thinkacpi in control. Now I have a problem with the OSD not showing the levels correctly but reading around this is known and maybe solvable.