背光

  LCD屏幕的背光支持0~7挡的亮度调节，默认亮度值为6挡。

1. 查看背光的最大等级

   # cat /sys/class/backlight/backlight/max_brightness

2. 设置背光的等级

   # echo 2 > /sys/class/backlight/backlight/brightness

3. 查看当前背光等级

   # cat /sys/class/backlight/backlight/brightness