Comment 41 for bug 1270579

some workaround:
to disable touchpad, add a line in .bashrc
gsettings set org.gnome.settings-daemon.peripherals.touchpad touchpad-enabled false

another way to adjust brightness:
1. cd /sys/class/backlight/$COM_backlight/
2. check the value in the file: max_brightness
3. sudo open the file:brightness and set it to [0, max-brightness), NOTE: MUST < max-brightness.

for convinence, create a shell script, and sudo it.

#!/bin/bash
# NOTE: the prefer value MUST < max-brightness.
echo "you prefer value" > /sys/class/backlight/$COM_backlight/brightness

reference:
http://askubuntu.com/questions/540911/how-to-adjust-screen-brightness-in-ubuntu-14-04