ssize_t (*read)(struct tty_struct * tty, struct file * file,
unsigned char __user * buf, size_t nr);
ssize_t (*write)(struct tty_struct * tty, struct file * file,
ssize_t (*read)(struct tty_struct * tty, struct file * file,
unsigned char __user * buf, size_t nr);
ssize_t (*write)(struct tty_struct * tty, struct file * file,