typedef struct PhysUart PhysUart;typedef struct Uart Uart; /* *  routines to access UART hardware */struct PhysUart{	char*	name;	Uart*	(*pnp)(void);	void	(*enable)(Uart*, int);	void	(*disable)(Uart*);	void	(*kick)(Uart*);	void	(*dobreak)(Uart*, int);	int	(*baud)(Uart*, int);	int	(*bits)(Uart*, int);	int	(*stop)(Uart*, int);	int	(*parity)(Uart*, int);	void	(*modemctl)(Uart*, int);	void	(*rts)(Uart*, int);	void	(*dtr)(Uart*, int);	long	(*status)(Uart*, void*, long, long);	void	(*fifo)(Uart*, int);	void	(*power)(Uart*, int);	int	(*getc)(Uart*);	/* polling versions, for iprint, rdb */	void	(*putc)(Uart*, int);}; enum {	Stagesize=	1024}; /* *  software UART */struct Uart{	void*	regs;			/* hardware stuff */	void*	saveregs;		/* place to put registers on power down */	char*	name;			/* internal name */	ulong	freq;			/* clock frequency */	int	bits;			/* bits per character */	int	stop;			/* stop bits */	int	parity;			/* even, odd or no parity */	int	baud;			/* baud rate */	PhysUart*phys;	int	console;		/* used as a serial console */	int	special;		/* internal kernel device */	Uart*	next;			/* list of allocated uarts */ 	QLock;	int	type;			/* ?? */	int	dev;	int	opens; 	int	enabled;	Uart	*elist;			/* next enabled interface */ 	int	perr;			/* parity errors */	int	ferr;			/* framing errors */	int	oerr;			/* rcvr overruns */	int	berr;			/* no input buffers */	int	serr;			/* input queue overflow */ 	/* buffers */	int	(*putc)(Queue*, int);	Queue	*iq;	Queue	*oq; 	Lock	rlock;	uchar	istage[Stagesize];	uchar	*iw;	uchar	*ir;	uchar	*ie; 	Lock	tlock;			/* transmit */	uchar	ostage[Stagesize];	uchar	*op;	uchar	*oe;	int	drain; 	int	modem;			/* hardware flow control on */	int	xonoff;			/* software flow control on */	int	blocked;	int	cts, dsr, dcd, dcdts;	/* keep track of modem status */ 	int	ctsbackoff;	int	hup_dsr, hup_dcd;	/* send hangup upstream? */	int	dohup; 	Rendez	r;}; extern Uart*	consuart; extern int	uartctl(Uart*, char*);extern int	uartgetc(void);extern void	uartkick(void*);extern void	uartmouse(Uart*, int (*)(Queue*, int), int);extern void	uartsetmouseputc(Uart*, int (*)(Queue*, int));extern void	uartputc(int);extern void	uartputs(char*, int);extern void	uartrecv(Uart*, char);extern Uart*	uartsetup(Uart*);extern int		uartstageoutput(Uart*);