Ubuntu
linux package

  1. Bug #1098216
  2. Comment #40

Comment 40 for bug 1098216

Revision history for this message
Seth Forshee (sforshee) wrote : Re: Regression in brightness control on Lenovo Thinkpad X230 and X1 Carbon

Nathaniel: You did try to change the brightness before collecting dmesg, and it did not change the brightness? I'm not seeing the errors I expected, though I'm confident they should occur because they happen when I load your ACPI tables into a debugger.

Maybe try poking some brightness values into the driver directly and see if you get any new messages at the bottom of dmesg. To do this, you'll first want to run 'cat /sys/class/backlight/acpi_video0/max_brightness'. This should output something like 101; if you get something much lower than that (like 15) then you still have acpi_osi="!Windows 2012" applied somehow.

Valid brightness values are anything from 0 to the value you get from the cat command. You set a value by running 'echo n > /sys/class/backlight/acpi_video0/brightness' as root, where n is a valid brightness value. Just be careful of going too low, you still want to be able to read the screen!