亦问lcd亮度问题

Rafa

xrandr --prop
Screen 0: minimum 320 x 200, current 1024 x 768, maximum 1024 x 1024
VGA-0 disconnected (normal left inverted right x axis y axis)
        load_detection: 1 (0x00000001) range:  (0,1)
DVI-0 disconnected (normal left inverted right x axis y axis)
                dvi_monitor_type: auto
                scaler: off
                tmds_pll: bios
        coherent_mode: 0 (0x00000000) range:  (0,1)
        load_detection: 1 (0x00000001) range:  (0,1)
LVDS connected 1024x768+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
                scaler: full
        backlight: 255 (0x000000ff) range:  (0,255)
   1024x768       60.0*+   60.0  
   800x600        60.3     59.9  
   640x480        59.9     59.4  
S-video disconnected (normal left inverted right x axis y axis)
                tv_standard: ntsc
        tv_vertical_position: 0 (0x00000000) range:  (-5,5)
        tv_horizontal_position: 0 (0x00000000) range:  (-5,5)
        tv_horizontal_size: 0 (0x00000000) range:  (-5,5)
        load_detection: 0 (0x00000000) range:  (0,1)



然后xrandr --output LVDS --set backlight [VALUE]
无论[VALUE]值调为(0,255)内任意数字，屏幕的亮光一点变化也没有。

这是咋么搞的