使用cat echo控制linux字节型硬件

在判断出来 
    else if(strcmp(state,LCD_BRIGHTNESS_OFF) == 0)后
    plight = "0";
那么，fd = open(LCD_BACKLIGHT_BRIGHTNESS_PATH,O_RDWR|O_TRUNC); 
用si跟踪出来
#define LCD_BACKLIGHT_BRIGHTNESS_PATH  "/sys/class/leds/lcd-backlight/brightness"

打开这个目录后，

if(write(fd, plight, strlen(plight)) < 0)，再将为0的plight写入到这个节点，
这样来实现屏灭。肯定还有一个目录为/sys/class/leds/keyboard-backlight/brightness，先不急写代码，实现一下吧。

把手机插上电脑，adb shell连接上去，
/sys/class/leds/keyboard-backlight/brightness，继续验证一下

#cat brightness
0
现在是LED灭的状态

#echo >brightness 100

见证奇迹的时刻，LED亮了，


echo 23 > /sys/devices/platform/atmel_lcdfb.0/backlight/backlight/brightness

/sys/class/leds/keyboard-backlight/brightness
#cat brightness
0
#echo >brightness 100