应用到驱动的数值传递

    int ret = -1;

   #define IRSENSOR_TEST1   _IOR(IRSENSOR_IOC_MAGIC, 0x12, int)

    int   _fd    = open("/dev/ir_sensor",8);

    ioctl(_fd, IRSENSOR_TEST1, &ret);   

static long irsensor_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{


       int ret=0;
    void __user *argp = (void __user *)arg;

    copy_to_user(argp, (void *)&ret,sizeof(ret));

}