さっき書いた方法では，少しラグっぽい動きをするので，xbacklightを使わないように変更してみた．
thinkpad_acpiが動く状況では，
# echo "up" > /proc/acpi/ibm/brightness
# echo "down" > /proc/acpi/ibm/brightness
でバックライトの調整ができるので，これを使って，
- /etc/acpi/video_brightnessdown.sh
#!/bin/sh
# lower the brightness by one level
#xbacklight -dec 10%
echo "down" > /proc/acpi/ibm/brightness
- /etc/acpi/video_brightnessup.sh
#!/bin/sh
# up the brightness by one level
#xbacklight -inc 10%
echo "up" > /proc/acpi/ibm/brightness
と変更．
