int megadev_ioctl (struct inode * inode, struct file * filep, unsigned int cmd, unsigned long arg);
inode - Our device inode filep - unused cmd - ioctl command arg - user buffer
ioctl entry point for our private ioctl interface. We move the data in from the user space, prepare the command (if necessary, convert the old MIMD ioctl to new ioctl command), and issue a synchronous command to the controller.