if(cnt > tmp)
				cnt = tmp;	/* Limit to data on hand */
			fp->cnt -= cnt;
			restore(i_state);
			break;
		}
		restore(i_state);
		if((errno = kwait(fp)) != 0)
			return -1;
	}		
	tmp = cnt;
	while(tmp-- != 0){
		/* This can be optimized later if necessary */
		c = *fp->rp++;
		if(fp->rp >= &fp->buf[fp->bufsize])
			fp->rp = fp->buf;
		*obp++ = c;
	}
	return cnt;
}
/* Blocking read from asynch line
 * Returns character or -1 if aborting
 */
int
get_asy(dev)
int dev;
{
	uint8 c;
	int tmp;

	if((tmp = asy_read(dev,&c,1)) == 1)
		return c;
	else
		return tmp;
}

/* Interrupt handler for 8250 asynch chip (called from asyvec.asm) */
INTERRUPT (far *(asyint)(dev))()
int dev;
{
	return asycom(&Asy[dev]);
}
/* Interrupt handler for AST 4-port board (called from fourport.asm) */
INTERRUPT (far *(fpint)(dev))()
int dev;
{
	int iv;
	struct fport *fport;
	int i;

	fport = &Fport[dev];
	/* Read special interrupt demux register to see which port is active */
	while(((iv = inportb(fport->iv)) & 0xf) != 0xf){
		for(i=0;i<4;i++){
			if((iv & (1 << i)) == 0 && fport->asy[i] != NULL)
				asycom(fport->asy[i]);
		}
	}
	return NULL;
}
/* Common interrupt handler code for 8250/16550 port */
static INTERRUPT (far *(asycom)(asyp))(void)
struct asy *asyp;
{
	unsigned base;
	char iir;

	base = asyp->addr;
	while(((iir = inportb(base+IIR)) & IIR_IP) == 0){
		switch(iir & IIR_ID_MASK){
		case IIR_RDA:	/* Receiver interrupt */
			asyrxint(asyp);
			break;
		case IIR_THRE:	/* Transmit interrupt */
			asytxint(asyp);
			break;
		case IIR_MSTAT:	/* Modem status change */
			asymsint(asyp);
			asyp->msint_count++;
			break;
		}
		/* should happen at end of a single packet */
		if(iir & IIR_FIFO_TIMEOUT)
			asyp->fifotimeouts++;
	}
	return asyp->chain ? asyp->save.vec : NULL;
}


/* Process 8250 receiver interrupts */
static int
asyrxint(asyp)
struct asy *asyp;
{
	register struct fifo *fp;
	unsigned base;
	uint8 c,lsr;
	int cnt = 0;
	int trigseen = FALSE;

	asyp->rxints++;
	base = asyp->addr;
	fp = &asyp->fifo;
	for(;;){
		lsr = inportb(base+LSR);
		if(lsr & LSR_OE)
			asyp->overrun++;

		if(lsr & LSR_DR){
			asyp->rxchar++;
			c = inportb(base+RBR);
			if(asyp->trigchar == -1 || asyp->trigchar == c)
				trigseen = TRUE;
			/* If buffer is full, we have no choice but
			 * to drop the character
			 */
			if(fp->cnt != fp->bufsize){
				*fp->wp++ = c;
				if(fp->wp >= &fp->buf[fp->bufsize])
					/* Wrap around */
					fp->wp = fp->buf;
				fp->cnt++;
				if(fp->cnt > fp->hiwat)
					fp->hiwat = fp->cnt;
				cnt++;
			} else
				fp->overrun++;
		} else
			break;
	}
	if(cnt > asyp->rxhiwat)
		asyp->rxhiwat = cnt;
	if(trigseen)
		ksignal(fp,1);
	return cnt;
}


/* Handle 8250 transmitter interrupts */
static void
asytxint(asyp)
struct asy *asyp;
{
	register struct dma *dp;
	register unsigned base;
	register int count;

	base = asyp->addr;
	dp = &asyp->dma;
	asyp->txints++;
	if(!dp->busy || (asyp->cts && !(asyp->msr & MSR_CTS))){
		/* These events "shouldn't happen". Either the
		 * transmitter is idle, in which case the transmit
		 * interrupts should have been disabled, or flow control
		 * is enabled but CTS is low, and interrupts should also
		 * have been disabled.
		 */
		clrbit(base+IER,IER_TxE);
		return;	/* Nothing to send */
	}
	if(!(inportb(base+LSR) & LSR_THRE))
		return;	/* Not really ready */

	/* If it's a 16550A, load up to 16 chars into the tx hw fifo
	 * at once. With an 8250, it can be one char at most.
	 */
	if(asyp->is_16550a){
		count = min(dp->cnt,OUTPUT_FIFO_SIZE);

		/* 16550A: LSR_THRE will drop after the first char loaded
		 * so we can't look at this bit to determine if the hw fifo is
		 * full. There seems to be no way to determine if the tx fifo
		 * is full (any clues?). So we should never get here while the
		 * fifo isn't empty yet.
		 */
		asyp->txchar += count;
		dp->cnt -= count;
#ifdef	notdef	/* This is apparently too fast for some chips */
		dp->data = outbuf(base+THR,dp->data,count);
#else
		while(count-- != 0)
			outportb(base+THR,*dp->data++);
#endif
	} else {	/* 8250 */
		do {
			asyp->txchar++;
			outportb(base+THR,*dp->data++);
		} while(--dp->cnt != 0 && (inportb(base+LSR) & LSR_THRE));
	}
	if(dp->cnt == 0){
		dp->busy = 0;
		/* Disable further transmit interrupts */
		clrbit(base+IER,IER_TxE);
		ksignal(&asyp->dma,1);
	}
}

/* Handle 8250 modem status change interrupt */
static void
asymsint(asyp)
struct asy *asyp;
{
	unsigned base = asyp->addr;

	asyp->msr = inportb(base+MSR);

	if(asyp->cts && (asyp->msr & MSR_DCTS)){
		/* CTS has changed and we care */
		if(asyp->msr & MSR_CTS){
			/* CTS went up */
			if(asyp->dma.busy){
				/* enable transmit interrupts and kick */
				setbit(base+IER,IER_TxE);
				asytxint(asyp);
			}
		} else {
			/* CTS now dropped, disable Transmit interrupts */
			clrbit(base+IER,IER_TxE);
		}
	}
	if(asyp->rlsd && (asyp->msr & MSR_DRLSD)){
		/* RLSD just changed and we care, signal it */
		ksignal( &(asyp->rlsd), 1 );
		/* Keep count */
		asyp->cdchanges++;
	}
	ksignal(&asyp->msr,0);
}

/* Wait for a signal that the RLSD modem status has changed */
int
get_rlsd_asy(dev, new_rlsd)
int dev;
int new_rlsd;
{
	struct asy *ap = &Asy[dev];

	if(ap->rlsd == 0)
		return -1;

	for(;;){
		if(new_rlsd && (ap->msr & MSR_RLSD))
			return 1;
		if(!new_rlsd && !(ap->msr & MSR_RLSD))
			return 0;

		/* Wait for state change to requested value */
		ppause(2L);
		kwait( &(ap->rlsd) );
	}
}

/* Poll the asynch input queues; called on every clock tick.
 * This helps limit the interrupt ring buffer occupancy when long
 * packets are being received.
 */
void
asytimer()
{
	register struct asy *asyp;
	register struct fifo *fp;
	register int i;
	int i_state;

	for(i=0;i<ASY_MAX;i++){
		asyp = &Asy[i];
		fp = &asyp->fifo;
		if(fp->cnt != 0)
			ksignal(fp,1);
		if(asyp->dma.busy
		 && (inportb(asyp->addr+LSR) & LSR_THRE)
		 && (!asyp->cts || (asyp->msr & MSR_CTS))){
			asyp->txto++;
			i_state = dirps();
			asytxint(asyp);
			restore(i_state);
		}
	}
}
int
doasystat(argc,argv,p)
int argc;
char *argv[];
void *p;
{
	register struct asy *asyp;
	struct iface *ifp;
	int i;

	if(argc < 2){
		for(asyp = Asy;asyp < &Asy[ASY_MAX];asyp++){
			if(asyp->iface != NULL)
				pasy(asyp);
		}
		return 0;
	}
	for(i=1;i<argc;i++){
		if((ifp = if_lookup(argv[i])) == NULL){
			printf("Interface %s unknown\n",argv[i]);
			continue;
		}
		for(asyp = Asy;asyp < &Asy[ASY_MAX];asyp++){
			if(asyp->iface == ifp){
				pasy(asyp);
				break;
			}
		}
		if(asyp == &Asy[ASY_MAX])
			printf("Interface %s not asy\n",argv[i]);
	}

	return 0;
}

static void
pasy(asyp)
struct asy *asyp;
{
	int mcr;

	printf("%s:",asyp->iface->name);
	if(asyp->is_16550a)
		printf(" [NS16550A]");
	if(asyp->trigchar != -1)
		printf(" [trigger 0x%02x]",asyp->trigchar);
	if(asyp->cts)
		printf(" [cts flow control]");
	if(asyp->rlsd)
		printf(" [rlsd line control]");

	printf(" %lu bps\n",asyp->speed);

	mcr = inportb(asyp->addr+MCR);
	printf(" MC: int %lu DTR %s  RTS %s  CTS %s  DSR %s  RI %s  CD %s\n",
	 asyp->msint_count,
	 (mcr & MCR_DTR) ? "On" : "Off",
	 (mcr & MCR_RTS) ? "On" : "Off",
	 (asyp->msr & MSR_CTS) ? "On" : "Off",
	 (asyp->msr & MSR_DSR) ? "On" : "Off",
	 (asyp->msr & MSR_RI) ? "On" : "Off",
	 (asyp->msr & MSR_RLSD) ? "On" : "Off");
	
	printf(" RX: int %lu chars %lu hw over %lu hw hi %lu",
	 asyp->rxints,asyp->rxchar,asyp->overrun,asyp->rxhiwat);
	asyp->rxhiwat = 0;
	if(asyp->is_16550a)
		printf(" fifo TO %lu",asyp->fifotimeouts);
	printf(" sw over %lu sw hi %u\n",
	 asyp->fifo.overrun,asyp->fifo.hiwat);
	asyp->fifo.hiwat = 0;

	printf(" TX: int %lu chars %lu THRE TO %lu%s\n",
	 asyp->txints,asyp->txchar,asyp->txto,
	 asyp->dma.busy ? " BUSY" : "");
}
/* Send a message on the specified serial line */
int
asy_send(dev,bpp)
int dev;
struct mbuf **bpp;
{
	if(dev < 0 || dev >= ASY_MAX){
		free_p(bpp);
		return -1;
	}
	while(*bpp != NULL){
		/* Send the buffer */
		asy_write(dev,(*bpp)->data,(*bpp)->cnt);
		/* Now do next buffer on chain */
		*bpp = free_mbuf(bpp);
	}
	return 0;
}
/* Attach an AST 4-port serial interface (or clone) to the system
 * argv[0]: hardware type, must be "4port"
 * argv[1]: I/O address, e.g., "0x2a0"
 * argv[2]: vector, e.g., "5",
 */
int
fp_attach(argc,argv,p)
int argc;
char *argv[];
void *p;
{
	int i;
	struct fport *fp;

	for(i=0;i<FPORT_MAX;i++){
		if(Fport[i].base == 0)
			break;
	}
	if(i == FPORT_MAX){
		printf("Too many 4port devices\n");
		return 1;
	}
	fp = &Fport[i];
	fp->base = htoi(argv[1]);
	fp->irq = atoi(argv[2]);
	fp->iv = fp->base + 0x1f;
	setirq(fp->irq,Fphand[i]);
	maskon(fp->irq);
	outportb(fp->iv,0x80);	/* Enable global interrupts */
	return 0;
}
void
fp_stop()
{
	int i;
	struct fport *fp;

	for(i=0;i<FPORT_MAX;i++){
		if(Fport[i].base == 0)
			continue;
		fp = &Fport[i];
		outportb(fp->iv,0);	/* Disable global interrupts */
		maskoff(fp->irq);
	}
}