Xbacklight can only decrease brightness

Question

I'm running Ubuntu 10.10 on a Cr48. I'm attempting to bind xbacklight -dec 10 to f6 (decrease brightness in chrome os) and xbacklight -inc 10 to f7 (increase brightness in chrome os). The decrease command works fine, but the increase command appears to have no effect. It's the same whether I run the command from the command line or use the bindings I set in CompizConfig Settings Manager.

Answer 1

You can change the brightness by changing some setting files.

1. Open a terminal

2. Login as root. sudo su

3. Type echo -n 100 > /proc/acpi/video/DVGA/LCD/brightness.

4. If you get a "No such file or directory" error, replace DVGA with VGA.

5. 100 is the highest brightness level (100%). For example, just change the 100 to 50, to dim your display by 50 percent.

I hope this helped you and I don't know if it's possible to fix this bug with xbacklight. If you really want to work with xbacklight, I'd create a bug report.

-- Daniel

Answer 2

I had this same issue at first... I think it's that the default is to take 20 steps to complete the transition... this combined with your small 10% change breaks things it seems.

I got mine to work by making my functions as such:

brightness up => xbacklight -steps 1 -inc 20 brightness down => xbacklight -steps 1 -dec 20

• Also, I saw in the above answer about LCD vs OVGA. You won't get LCD becuase it's a notebook. They should be OVGA ... something like: /proc/acpi/video/OVGA/DD01/

But if you setup your steps to be 1 and increase your percent changes to 20 or more you should be just fine with xbacklight!