1.在init.rc中提权 chmod 777 /dev/ttyUSB0
init.rc文件在system/core/rootdir
2.在device.c中提权限，这个比较隐蔽，不易发现
device.c 在/system/core/init/device.c
3.每次都在java层去提权，cmd为提权命令
public void exeShell(String cmd){
try{
Process p = Runtime.getRuntime().exec(cmd);
BufferedReader in = new BufferedReader(
new InputStreamReader(
p.getInputStream()));
String line = null;
while ((line = in.readLine()) != null) {
Log.i("exeShell",line);
}
}
catch(Throwable t)
{
t.printStackTrace();
}
}
详细见 http://blog.csdn.net/yiyaaixuexi/article/details/6803593