/* * Used to dissect integer device code * into major (driver designation) and * minor (driver parameter) parts. */struct{	char	d_minor;	char	d_major;};/* * 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. */struct	bdevsw{	int	(*d_open)();	int	(*d_close)();	int	(*d_strategy)();	int	*d_tab;} bdevsw[];/* * Nblkdev is the number of entries * (rows) in the block switch. It is * set in binit/bio.c by making * a pass over the switch. * Used in bounds checking on major * device numbers. */int	nblkdev;/* * Character device switch. */struct	cdevsw{	int	(*d_open)();	int	(*d_close)();	int	(*d_read)();	int	(*d_write)();	int	(*d_sgtty)();} cdevsw[];/* * Number of character switch entries. * Set by cinit/tty.c */int	nchrdev;