/* * Declaration of block device * switch. Each entry (row) is * the only link between the * main unix code and the driver. * The initialization of the * device switches is in the * file conf.c. */extern struct bdevsw{	int	(*d_open)();	int	(*d_close)();	int	(*d_strategy)();	struct buf *d_tab;} bdevsw[];/* * Character device switch. */extern struct cdevsw{	int	(*d_open)();	int	(*d_close)();	int	(*d_read)();	int	(*d_write)();	int	(*d_ioctl)();	int	(*d_stop)();	struct tty *d_ttys;} cdevsw[];/* * tty line control switch. */extern struct linesw{	int	(*l_open)();	int	(*l_close)();	int	(*l_read)();	char	*(*l_write)();	int	(*l_ioctl)();	int	(*l_rint)();	int	(*l_rend)();	int	(*l_meta)();	int	(*l_start)();	int	(*l_modem)();} linesw[];