path: root/sys/arch/i386/isa/pccom.c

/*	$OpenBSD: pccom.c,v 1.52 2006/06/15 15:44:45 jason Exp $	*/
/*	$NetBSD: com.c,v 1.82.4.1 1996/06/02 09:08:00 mrg Exp $	*/

/*
 * Copyright (c) 1997 - 1999, Jason Downs.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name(s) of the author(s) nor the name OpenBSD
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS
 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */
/*-
 * Copyright (c) 1993, 1994, 1995, 1996
 *	Charles M. Hannum.  All rights reserved.
 * Copyright (c) 1991 The Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	@(#)com.c	7.5 (Berkeley) 5/16/91
 */

/*
 * PCCOM driver, uses National Semiconductor NS16450/NS16550AF UART
 */
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/ioctl.h>
#include <sys/selinfo.h>
#include <sys/tty.h>
#include <sys/proc.h>
#include <sys/user.h>
#include <sys/conf.h>
#include <sys/file.h>
#include <sys/uio.h>
#include <sys/kernel.h>
#include <sys/syslog.h>
#include <sys/types.h>
#include <sys/device.h>
#include <sys/vnode.h>
#include <sys/timeout.h>

#include <machine/bus.h>
#include <machine/intr.h>

#include <dev/cons.h>
#include <dev/isa/isavar.h>
#include <dev/ic/comreg.h>
#include <dev/ic/ns16550reg.h>
#define	com_lcr	com_cfcr
#ifdef DDB
#include <ddb/db_var.h>
#endif

#include "pccomvar.h"
#include "pccom.h"

/* XXX: These belong elsewhere */
cdev_decl(com);

static u_char tiocm_xxx2mcr(int);

void pccom_xr16850_fifo_init(bus_space_tag_t, bus_space_handle_t);

/*
 * XXX the following two cfattach structs should be different, and possibly
 * XXX elsewhere.
 */
int	comprobe(struct device *, void *, void *);
void	comattach(struct device *, struct device *, void *);
void	compwroff(struct com_softc *);

#if NPCCOM_ISA
struct cfattach pccom_isa_ca = {
	sizeof(struct com_softc), comprobe, comattach
};
#endif

#if NPCCOM_ISAPNP
struct cfattach pccom_isapnp_ca = {
	sizeof(struct com_softc), comprobe, comattach
};
#endif

#if NPCCOM_COMMULTI
struct cfattach pccom_commulti_ca = {
	sizeof(struct com_softc), comprobe, comattach
};
#endif

struct cfdriver pccom_cd = {
	NULL, "pccom", DV_TTY
};

void cominit(bus_space_tag_t, bus_space_handle_t, int);

#ifndef CONSPEED
#define	CONSPEED B9600
#endif

#if defined(COMCONSOLE) || defined(PCCOMCONSOLE)
int	comdefaultrate = CONSPEED;		/* XXX why set default? */
#else
int	comdefaultrate = TTYDEF_SPEED;
#endif
bus_addr_t comconsaddr;
int	comconsinit;
int	comconsattached;
bus_space_tag_t comconsiot;
bus_space_handle_t comconsioh;
tcflag_t comconscflag = TTYDEF_CFLAG;

int	commajor;
int	comsopen = 0;
int	comevents = 0;

#ifdef KGDB
#include <sys/kgdb.h>

bus_addr_t com_kgdb_addr;
bus_space_tag_t com_kgdb_iot;
bus_space_handle_t com_kgdb_ioh;

int	com_kgdb_getc(void *);
void	com_kgdb_putc(void *, int);
#endif /* KGDB */

#define	DEVUNIT(x)	(minor(x) & 0x7f)
#define	DEVCUA(x)	(minor(x) & 0x80)

/* Macros for determining bus type. */
#if NPCCOM_ISA || NPCCOM_PCMCIA
#define IS_ISA(parent) \
	(!strcmp((parent)->dv_cfdata->cf_driver->cd_name, "isa") || \
	 !strcmp((parent)->dv_cfdata->cf_driver->cd_name, "pcmcia"))
#elif NPCCOM_ISA
#define IS_ISA(parent) \
	!strcmp((parent)->dv_cfdata->cf_driver->cd_name, "isa")
#elif NPCCOM_ISAPNP
#define IS_ISA(parent) 0
#endif

#if NPCCOM_ISAPNP
#define IS_ISAPNP(parent) \
	 !strcmp((parent)->dv_cfdata->cf_driver->cd_name, "isapnp")
#else
#define IS_ISAPNP(parent)	0
#endif

int
comspeed(freq, speed)
	long freq;
	long speed;
{
#define	divrnd(n, q)	(((n)*2/(q)+1)/2)	/* divide and round off */

	int x, err;

	if (speed == 0)
		return 0;
	if (speed < 0)
		return -1;
	x = divrnd((freq / 16), speed);
	if (x <= 0)
		return -1;
	err = divrnd((quad_t)freq * 1000 / 16, speed * x) - 1000;
	if (err < 0)
		err = -err;
	if (err > COM_TOLERANCE)
		return -1;
	return x;

#undef	divrnd
}

int
comprobe1(iot, ioh)
	bus_space_tag_t iot;
	bus_space_handle_t ioh;
{
	int i, k;

	/* force access to id reg */
	bus_space_write_1(iot, ioh, com_lcr, 0);
	bus_space_write_1(iot, ioh, com_iir, 0);
	for (i = 0; i < 32; i++) {
		k = bus_space_read_1(iot, ioh, com_iir);
		if (k & 0x38) {
			bus_space_read_1(iot, ioh, com_data); /* cleanup */
		} else
			break;
	}
	if (i >= 32) 
	    return 0;

	return 1;
}

int
comprobe(parent, match, aux)
	struct device *parent;
	void *match, *aux;
{
	bus_space_tag_t iot;
	bus_space_handle_t ioh;
	int iobase, needioh;
	int rv = 1;

	/*
	 * XXX should be broken out into functions for isa probe and
	 * XXX for commulti probe, with a helper function that contains
	 * XXX most of the interesting stuff.
	 */
/* #if NPCCOM_ISA || NPCCOM_PCMCIA || NPCCOM_ISAPNP */
#if NPCCOM_ISA || NPCCOM_ISAPNP
	if (IS_ISA(parent) || IS_ISAPNP(parent)) {
		struct isa_attach_args *ia = aux;

		iot = ia->ia_iot;
		iobase = ia->ia_iobase;
		if (IS_ISAPNP(parent)) {
			ioh = ia->ia_ioh;
			needioh = 0;
		} else
			needioh = 1;
	} else
#endif
#if NPCCOM_COMMULTI
	if (1) {
		struct cfdata *cf = match;
		struct commulti_attach_args *ca = aux;
 
		if (cf->cf_loc[0] != -1 && cf->cf_loc[0] != ca->ca_slave)
			return (0);

		iot = ca->ca_iot;
		iobase = ca->ca_iobase;
		ioh = ca->ca_ioh;
		needioh = 0;
	} else
#endif
		return(0);			/* This cannot happen */

#ifdef KGDB
	if (iobase == com_kgdb_addr)
		goto out;
#endif /* KGDB */

	/* if it's in use as console, it's there. */
	if (iobase == comconsaddr && !comconsattached)
		goto out;

	if (needioh && bus_space_map(iot, iobase, COM_NPORTS, 0, &ioh)) {
		rv = 0;
		goto out;
	}
	rv = comprobe1(iot, ioh);
	if (needioh)
		bus_space_unmap(iot, ioh, COM_NPORTS);

out:
/* #if NPCCOM_ISA || NPCCOM_PCMCIA */
#if NPCCOM_ISA
	if (rv) {
		struct isa_attach_args *ia = aux;

		ia->ia_iosize = COM_NPORTS;
		ia->ia_msize = 0;
	}
#endif
	return (rv);
}

void
comattach(parent, self, aux)
	struct device *parent, *self;
	void *aux;
{
	struct com_softc *sc = (void *)self;
	bus_addr_t iobase;
	bus_space_tag_t iot;
	bus_space_handle_t ioh;
	int irq;

	/*
	 * XXX should be broken out into functions for isa attach and
	 * XXX for commulti attach, with a helper function that contains
	 * XXX most of the interesting stuff.
	 */
/* #if NPCCOM_ISA || NPCCOM_PCMCIA || NPCCOM_ISAPNP */
#if NPCCOM_ISA || NPCCOM_ISAPNP
	if (IS_ISA(parent) || IS_ISAPNP(parent)) {
		struct isa_attach_args *ia = aux;

		/*
		 * We're living on an isa.
		 */
		iobase = ia->ia_iobase;
		iot = ia->ia_iot;
		if (IS_ISAPNP(parent)) {
			/* No console support! */
			ioh = ia->ia_ioh;
		} else {
#ifdef KGDB
			if ((iobase != comconsaddr) &&
			    (iobase != com_kgdb_addr)) {
#else
	       		if (iobase != comconsaddr) {
#endif /* KGDB */
				if (bus_space_map(iot, iobase, COM_NPORTS, 0, &ioh))
					panic("comattach: io mapping failed");
			} else
#ifdef KGDB
				if (iobase == comconsaddr) {
					ioh = comconsioh;
				} else {
					ioh = com_kgdb_ioh;
				}
#else
				ioh = comconsioh;
#endif /* KGDB */
		}
		irq = ia->ia_irq;
	} else
#endif
#if NPCCOM_COMMULTI
	if (1) {
		struct commulti_attach_args *ca = aux;

		/*
		 * We're living on a commulti.
		 */
		iobase = ca->ca_iobase;
		iot = ca->ca_iot;
		ioh = ca->ca_ioh;
		irq = IRQUNK;

		if (ca->ca_noien)
			SET(sc->sc_hwflags, COM_HW_NOIEN);
	} else
#endif
		panic("comattach: impossible");

	sc->sc_iot = iot;
	sc->sc_ioh = ioh;
	sc->sc_iobase = iobase;
	sc->sc_frequency = COM_FREQ;

	sc->sc_hwflags = 0;
	sc->sc_swflags = 0;

	if (irq != IRQUNK) {
		/* disable interrupts */
		bus_space_write_1(iot, ioh, com_ier, 0);

/* #if NPCCOM_ISA || NPCCOM_PCMCIA || NPCCOM_ISAPNP */
#if NPCCOM_ISA || NPCCOM_ISAPNP
		if (IS_ISA(parent) || IS_ISAPNP(parent)) {
			struct isa_attach_args *ia = aux;

#ifdef KGDB
			if (iobase == com_kgdb_addr) {
				sc->sc_ih = isa_intr_establish(ia->ia_ic, irq,
				    IST_EDGE, IPL_HIGH, kgdbintr, sc,
				    sc->sc_dev.dv_xname);
			} else {
				sc->sc_ih = isa_intr_establish(ia->ia_ic, irq,
				    IST_EDGE, IPL_HIGH, comintr, sc,
				    sc->sc_dev.dv_xname);
			}
#else
			sc->sc_ih = isa_intr_establish(ia->ia_ic, irq,
			    IST_EDGE, IPL_HIGH, comintr, sc,
			    sc->sc_dev.dv_xname);
#endif /* KGDB */
		} else
#endif
			panic("comattach: IRQ but can't have one");
	}

	com_attach_subr(sc);
}

int
com_detach(self, flags)
	struct device *self;
	int flags;
{
	struct com_softc *sc = (struct com_softc *)self;
	int maj, mn;

	/* locate the major number */
	for (maj = 0; maj < nchrdev; maj++)
		if (cdevsw[maj].d_open == comopen)
			break;

	/* Nuke the vnodes for any open instances. */
	mn = self->dv_unit;
	vdevgone(maj, mn, mn, VCHR);

	/* XXX a symbolic constant for the cua bit would be nicer. */
	mn |= 0x80;
	vdevgone(maj, mn, mn, VCHR);

	/* Detach and free the tty. */
	if (sc->sc_tty) {
		ttyfree(sc->sc_tty);
	}

	timeout_del(&sc->sc_dtr_tmo);
	timeout_del(&sc->sc_diag_tmo);

	return (0);
}

int
com_activate(self, act)
	struct device *self;
	enum devact act;
{
	struct com_softc *sc = (struct com_softc *)self;
	int s, rv = 0;

	/* XXX splserial, when we get that.  */
	s = spltty();
	switch (act) {
	case DVACT_ACTIVATE:
		rv = EOPNOTSUPP;
		break;

	case DVACT_DEACTIVATE:
#ifdef KGDB
		if (sc->sc_hwflags & (COM_HW_CONSOLE|COM_HW_KGDB)) {
#else
		if (sc->sc_hwflags & COM_HW_CONSOLE) {
#endif /* KGDB */
			rv = EBUSY;
			break;
		}

		if (sc->disable != NULL && sc->enabled != 0) {
			(*sc->disable)(sc);
			sc->enabled = 0;
		}
		break;
	}
	splx(s);
	return (rv);
}

int
comopen(dev, flag, mode, p)
	dev_t dev;
	int flag, mode;
	struct proc *p;
{
	int unit = DEVUNIT(dev);
	struct com_softc *sc;
	bus_space_tag_t iot;
	bus_space_handle_t ioh;
	struct tty *tp;
	int s;
	int error = 0;
 
	if (unit >= pccom_cd.cd_ndevs)
		return ENXIO;
	sc = pccom_cd.cd_devs[unit];
	if (!sc)
		return ENXIO;

#ifdef KGDB
	/*
	 * If this is the kgdb port, no other use is permitted.
	 */
	if (ISSET(sc->sc_hwflags, COM_HW_KGDB))
		return (EBUSY);
#endif /* KGDB */

	s = spltty();
	if (!sc->sc_tty) {
		tp = sc->sc_tty = ttymalloc();
	} else
		tp = sc->sc_tty;
	splx(s);

	tp->t_oproc = comstart;
	tp->t_param = comparam;
	tp->t_hwiflow = comhwiflow;
	tp->t_dev = dev;
	if (!ISSET(tp->t_state, TS_ISOPEN)) {
		SET(tp->t_state, TS_WOPEN);
		ttychars(tp);
		tp->t_iflag = TTYDEF_IFLAG;
		tp->t_oflag = TTYDEF_OFLAG;
		if (ISSET(sc->sc_hwflags, COM_HW_CONSOLE))
			tp->t_cflag = comconscflag;
		else
			tp->t_cflag = TTYDEF_CFLAG;
		if (ISSET(sc->sc_swflags, COM_SW_CLOCAL))
			SET(tp->t_cflag, CLOCAL);
		if (ISSET(sc->sc_swflags, COM_SW_CRTSCTS))
			SET(tp->t_cflag, CRTSCTS);
		if (ISSET(sc->sc_swflags, COM_SW_MDMBUF))
			SET(tp->t_cflag, MDMBUF);
		tp->t_lflag = TTYDEF_LFLAG;
		tp->t_ispeed = tp->t_ospeed = comdefaultrate;

		s = spltty();

		iot = sc->sc_iot;
		ioh = sc->sc_ioh;

		/*
		 * Wake up the sleepy heads.
		 */
		switch (sc->sc_uarttype) {
		case COM_UART_ST16650:
		case COM_UART_ST16650V2:
		case COM_UART_XR16850:
			bus_space_write_1(iot, ioh, com_lcr, LCR_EFR);
			bus_space_write_1(iot, ioh, com_efr, EFR_ECB);
			bus_space_write_1(iot, ioh, com_ier, 0);
			bus_space_write_1(iot, ioh, com_efr, 0);
			bus_space_write_1(iot, ioh, com_lcr, 0);
			break;
		case COM_UART_TI16750:
			bus_space_write_1(iot, ioh, com_ier, 0);
			break;
		}

		sc->sc_initialize = 1;
		comparam(tp, &tp->t_termios);
		ttsetwater(tp);

		sc->sc_rxput = sc->sc_rxget = sc->sc_tbc = 0;

		if (ISSET(sc->sc_hwflags, COM_HW_FIFO)) {
			u_int8_t fifo = FIFO_ENABLE|FIFO_RCV_RST|FIFO_XMT_RST;
			u_int8_t lcr;

			switch (sc->sc_uarttype) {
			case COM_UART_ST16650V2:
				if (tp->t_ispeed <= 1200)
					fifo |= FIFO_RCV_TRIGGER_8|FIFO_XMT_TRIGGER_8; /* XXX */
				else
					fifo |= FIFO_RCV_TRIGGER_28|FIFO_XMT_TRIGGER_30;
				break;
			case COM_UART_XR16850:
				pccom_xr16850_fifo_init(iot, ioh);
				if (tp->t_ispeed <= 1200)
					fifo |= FIFO_RCV3_TRIGGER_8|FIFO_XMT3_TRIGGER_8; /* XXX */
				else
					fifo |= FIFO_RCV3_TRIGGER_60|FIFO_XMT3_TRIGGER_56;
				break;
			case COM_UART_TI16750:
				fifo |= FIFO_ENABLE_64BYTE;
				lcr = bus_space_read_1(iot, ioh, com_lcr);
				bus_space_write_1(iot, ioh, com_lcr,
				    lcr | LCR_DLAB);
			default:
				if (tp->t_ispeed <= 1200)
					fifo |= FIFO_TRIGGER_1;
				else
					fifo |= FIFO_TRIGGER_8;
			}

			/*
			 * (Re)enable and drain FIFOs.
			 *
			 * Certain SMC chips cause problems if the FIFOs are
			 * enabled while input is ready. Turn off the FIFO
			 * if necessary to clear the input. Test the input
			 * ready bit after enabling the FIFOs to handle races
			 * between enabling and fresh input.
			 *
			 * Set the FIFO threshold based on the receive speed.
			 */
			for (;;) {
			 	bus_space_write_1(iot, ioh, com_fifo, 0);
				delay(100);
				(void) bus_space_read_1(iot, ioh, com_data);
				bus_space_write_1(iot, ioh, com_fifo, fifo |
				    FIFO_RCV_RST | FIFO_XMT_RST);
				delay(100);
				if(!ISSET(bus_space_read_1(iot, ioh,
				    com_lsr), LSR_RXRDY))
				    	break;
			}
			if (sc->sc_uarttype == COM_UART_TI16750)
				bus_space_write_1(iot, ioh, com_lcr, lcr);
		}

		/* flush any pending I/O */
		while (ISSET(bus_space_read_1(iot, ioh, com_lsr), LSR_RXRDY))
			(void) bus_space_read_1(iot, ioh, com_data);
		/* you turn me on, baby */
		sc->sc_mcr = MCR_DTR | MCR_RTS;
		if (!ISSET(sc->sc_hwflags, COM_HW_NOIEN))
			SET(sc->sc_mcr, MCR_IENABLE);
		bus_space_write_1(iot, ioh, com_mcr, sc->sc_mcr);
		sc->sc_ier = IER_ERXRDY | IER_ERLS | IER_EMSC;
		bus_space_write_1(iot, ioh, com_ier, sc->sc_ier);

		sc->sc_msr = bus_space_read_1(iot, ioh, com_msr);
		if (ISSET(sc->sc_swflags, COM_SW_SOFTCAR) || DEVCUA(dev) ||
		    ISSET(sc->sc_msr, MSR_DCD) || ISSET(tp->t_cflag, MDMBUF))
			SET(tp->t_state, TS_CARR_ON);
		else
			CLR(tp->t_state, TS_CARR_ON);
	} else if (ISSET(tp->t_state, TS_XCLUDE) && p->p_ucred->cr_uid != 0)
		return EBUSY;
	else
		s = spltty();

	if (DEVCUA(dev)) {
		if (ISSET(tp->t_state, TS_ISOPEN)) {
			/* Ah, but someone already is dialed in... */
			splx(s);
			return EBUSY;
		}
		sc->sc_cua = 1;		/* We go into CUA mode */
	} else {
		/* tty (not cua) device; wait for carrier if necessary */
		if (ISSET(flag, O_NONBLOCK)) {
			if (sc->sc_cua) {
				/* Opening TTY non-blocking... but the CUA is busy */
				splx(s);
				return EBUSY;
			}
		} else {
			while (sc->sc_cua ||
			       (!ISSET(tp->t_cflag, CLOCAL) &&
				!ISSET(tp->t_state, TS_CARR_ON))) {
				SET(tp->t_state, TS_WOPEN);
				error = ttysleep(tp, &tp->t_rawq, TTIPRI | PCATCH, ttopen, 0);
				/*
				 * If TS_WOPEN has been reset, that means the cua device
				 * has been closed.  We don't want to fail in that case,
				 * so just go around again.
				 */
				if (error && ISSET(tp->t_state, TS_WOPEN)) {
					CLR(tp->t_state, TS_WOPEN);
					if (!sc->sc_cua && !ISSET(tp->t_state, TS_ISOPEN))
						compwroff(sc);
					splx(s);
					return error;
				}
			}
		}
	}
	splx(s);
	return (*linesw[tp->t_line].l_open)(dev, tp);
}
 
int
comclose(dev, flag, mode, p)
	dev_t dev;
	int flag, mode;
	struct proc *p;
{
	int unit = DEVUNIT(dev);
	struct com_softc *sc = pccom_cd.cd_devs[unit];
	bus_space_tag_t iot = sc->sc_iot;
	bus_space_handle_t ioh = sc->sc_ioh;
	struct tty *tp = sc->sc_tty;
	int s;

	/* XXX This is for cons.c. */
	if (!ISSET(tp->t_state, TS_ISOPEN))
		return 0;

	(*linesw[tp->t_line].l_close)(tp, flag);
	s = spltty();
	if (ISSET(tp->t_state, TS_WOPEN)) {
		/* tty device is waiting for carrier; drop dtr then re-raise */
		CLR(sc->sc_mcr, MCR_DTR | MCR_RTS);
		bus_space_write_1(iot, ioh, com_mcr, sc->sc_mcr);
		timeout_add(&sc->sc_dtr_tmo, hz * 2);
	} else {
		/* no one else waiting; turn off the uart */
		compwroff(sc);
	}
	CLR(tp->t_state, TS_BUSY | TS_FLUSH);
	sc->sc_cua = 0;
	splx(s);
	ttyclose(tp);

#ifdef notyet /* XXXX */
	if (ISSET(sc->sc_hwflags, COM_HW_CONSOLE)) {
		ttyfree(tp);
		sc->sc_tty = 0;
	}
#endif
	return 0;
}

void
compwroff(sc)
	struct com_softc *sc;
{
	bus_space_tag_t iot = sc->sc_iot;
	bus_space_handle_t ioh = sc->sc_ioh;
	struct tty *tp = sc->sc_tty;

	CLR(sc->sc_lcr, LCR_SBREAK);
	bus_space_write_1(iot, ioh, com_lcr, sc->sc_lcr);
	bus_space_write_1(iot, ioh, com_ier, 0);
	if (ISSET(tp->t_cflag, HUPCL) &&
	    !ISSET(sc->sc_swflags, COM_SW_SOFTCAR)) {
		/* XXX perhaps only clear DTR */
		sc->sc_mcr = 0;
		bus_space_write_1(iot, ioh, com_mcr, sc->sc_mcr);
	}

	/*
	 * Turn FIFO off; enter sleep mode if possible.
	 */
	bus_space_write_1(iot, ioh, com_fifo, 0);
	delay(100);
	(void) bus_space_read_1(iot, ioh, com_data);
	delay(100);
	bus_space_write_1(iot, ioh, com_fifo,
			  FIFO_RCV_RST | FIFO_XMT_RST);

	switch (sc->sc_uarttype) {
	case COM_UART_ST16650:
	case COM_UART_ST16650V2:
	case COM_UART_XR16850:
		bus_space_write_1(iot, ioh, com_lcr, LCR_EFR);
		bus_space_write_1(iot, ioh, com_efr, EFR_ECB);
		bus_space_write_1(iot, ioh, com_ier, IER_SLEEP);
		bus_space_write_1(iot, ioh, com_lcr, 0);
		break;
	case COM_UART_TI16750:
		bus_space_write_1(iot, ioh, com_ier, IER_SLEEP);
		break;
	}
}

void
com_raisedtr(arg)
	void *arg;
{
	struct com_softc *sc = arg;

	SET(sc->sc_mcr, MCR_DTR | MCR_RTS);
	bus_space_write_1(sc->sc_iot, sc->sc_ioh, com_mcr, sc->sc_mcr);
}

int
comread(dev, uio, flag)
	dev_t dev;
	struct uio *uio;
	int flag;
{
	struct com_softc *sc = pccom_cd.cd_devs[DEVUNIT(dev)];
	struct tty *tp = sc->sc_tty;
 
	return ((*linesw[tp->t_line].l_read)(tp, uio, flag));
}
 
int
comwrite(dev, uio, flag)
	dev_t dev;
	struct uio *uio;
	int flag;
{
	struct com_softc *sc = pccom_cd.cd_devs[DEVUNIT(dev)];
	struct tty *tp = sc->sc_tty;
 
	return ((*linesw[tp->t_line].l_write)(tp, uio, flag));
}

struct tty *
comtty(dev)
	dev_t dev;
{
	struct com_softc *sc = pccom_cd.cd_devs[DEVUNIT(dev)];
	struct tty *tp = sc->sc_tty;

	return (tp);
}
 
static u_char
tiocm_xxx2mcr(data)
	int data;
{
	u_char m = 0;

	if (ISSET(data, TIOCM_DTR))
		SET(m, MCR_DTR);
	if (ISSET(data, TIOCM_RTS))
		SET(m, MCR_RTS);
	return m;
}

int
comioctl(dev, cmd, data, flag, p)
	dev_t dev;
	u_long cmd;
	caddr_t data;
	int flag;
	struct proc *p;
{
	int unit = DEVUNIT(dev);
	struct com_softc *sc = pccom_cd.cd_devs[unit];
	struct tty *tp = sc->sc_tty;
	bus_space_tag_t iot = sc->sc_iot;
	bus_space_handle_t ioh = sc->sc_ioh;
	int error;

	error = (*linesw[tp->t_line].l_ioctl)(tp, cmd, data, flag, p);
	if (error >= 0)
		return error;
	error = ttioctl(tp, cmd, data, flag, p);
	if (error >= 0)
		return error;

	switch (cmd) {
	case TIOCSBRK:
		SET(sc->sc_lcr, LCR_SBREAK);
		bus_space_write_1(iot, ioh, com_lcr, sc->sc_lcr);
		break;
	case TIOCCBRK:
		CLR(sc->sc_lcr, LCR_SBREAK);
		bus_space_write_1(iot, ioh, com_lcr, sc->sc_lcr);
		break;
	case TIOCSDTR:
		SET(sc->sc_mcr, sc->sc_dtr);
		bus_space_write_1(iot, ioh, com_mcr, sc->sc_mcr);
		break;
	case TIOCCDTR:
		CLR(sc->sc_mcr, sc->sc_dtr);
		bus_space_write_1(iot, ioh, com_mcr, sc->sc_mcr);
		break;
	case TIOCMSET:
		CLR(sc->sc_mcr, MCR_DTR | MCR_RTS);
	case TIOCMBIS:
		SET(sc->sc_mcr, tiocm_xxx2mcr(*(int *)data));
		bus_space_write_1(iot, ioh, com_mcr, sc->sc_mcr);
		break;
	case TIOCMBIC:
		CLR(sc->sc_mcr, tiocm_xxx2mcr(*(int *)data));
		bus_space_write_1(iot, ioh, com_mcr, sc->sc_mcr);
		break;
	case TIOCMGET: {
		u_char m;
		int bits = 0;

		m = sc->sc_mcr;
		if (ISSET(m, MCR_DTR))
			SET(bits, TIOCM_DTR);
		if (ISSET(m, MCR_RTS))
			SET(bits, TIOCM_RTS);
		m = sc->sc_msr;
		if (ISSET(m, MSR_DCD))
			SET(bits, TIOCM_CD);
		if (ISSET(m, MSR_CTS))
			SET(bits, TIOCM_CTS);
		if (ISSET(m, MSR_DSR))
			SET(bits, TIOCM_DSR);
		if (ISSET(m, MSR_RI | MSR_TERI))
			SET(bits, TIOCM_RI);
		if (bus_space_read_1(iot, ioh, com_ier))
			SET(bits, TIOCM_LE);
		*(int *)data = bits;
		break;
	}
	case TIOCGFLAGS: {
		int driverbits, userbits = 0;

		driverbits = sc->sc_swflags;
		if (ISSET(driverbits, COM_SW_SOFTCAR))
			SET(userbits, TIOCFLAG_SOFTCAR);
		if (ISSET(driverbits, COM_SW_CLOCAL))
			SET(userbits, TIOCFLAG_CLOCAL);
		if (ISSET(driverbits, COM_SW_CRTSCTS))
			SET(userbits, TIOCFLAG_CRTSCTS);
		if (ISSET(driverbits, COM_SW_MDMBUF))
			SET(userbits, TIOCFLAG_MDMBUF);

		*(int *)data = userbits;
		break;
	}
	case TIOCSFLAGS: {
		int userbits, driverbits = 0;

		error = suser(p, 0); 
		if (error != 0)
			return(EPERM); 

		userbits = *(int *)data;
		if (ISSET(userbits, TIOCFLAG_SOFTCAR) ||
		    ISSET(sc->sc_hwflags, COM_HW_CONSOLE))
			SET(driverbits, COM_SW_SOFTCAR);
		if (ISSET(userbits, TIOCFLAG_CLOCAL))
			SET(driverbits, COM_SW_CLOCAL);
		if (ISSET(userbits, TIOCFLAG_CRTSCTS))
			SET(driverbits, COM_SW_CRTSCTS);
		if (ISSET(userbits, TIOCFLAG_MDMBUF))
			SET(driverbits, COM_SW_MDMBUF);

		sc->sc_swflags = driverbits;
		break;
	}
	default:
		return ENOTTY;
	}

	return 0;
}

int
comparam(tp, t)
	struct tty *tp;
	struct termios *t;
{
	struct com_softc *sc = pccom_cd.cd_devs[DEVUNIT(tp->t_dev)];
	bus_space_tag_t iot = sc->sc_iot;
	bus_space_handle_t ioh = sc->sc_ioh;
	int ospeed = comspeed(sc->sc_frequency, t->c_ospeed);
	u_int8_t lcr;
	tcflag_t oldcflag;
	int s;

	/* check requested parameters */
	if (ospeed < 0 || (t->c_ispeed && t->c_ispeed != t->c_ospeed))
		return EINVAL;

	lcr = ISSET(sc->sc_lcr, LCR_SBREAK);

	switch (ISSET(t->c_cflag, CSIZE)) {
	case CS5:
		SET(lcr, LCR_5BITS);
		break;
	case CS6:
		SET(lcr, LCR_6BITS);
		break;
	case CS7:
		SET(lcr, LCR_7BITS);
		break;
	case CS8:
		SET(lcr, LCR_8BITS);
		break;
	}
	if (ISSET(t->c_cflag, PARENB)) {
		SET(lcr, LCR_PENAB);
		if (!ISSET(t->c_cflag, PARODD))
			SET(lcr, LCR_PEVEN);
	}
	if (ISSET(t->c_cflag, CSTOPB))
		SET(lcr, LCR_STOPB);

	sc->sc_lcr = lcr;

	s = spltty();

	if (ospeed == 0) {
		CLR(sc->sc_mcr, MCR_DTR);
		bus_space_write_1(iot, ioh, com_mcr, sc->sc_mcr);
	}

	/*
	 * Set the FIFO threshold based on the receive speed, if we are
	 * changing it.
	 */
	if (sc->sc_initialize || (tp->t_ispeed != t->c_ispeed)) {
		sc->sc_initialize = 0;

		if (ospeed != 0) {
			/*
			 * Make sure the transmit FIFO is empty before
			 * proceeding.  If we don't do this, some revisions
			 * of the UART will hang.  Interestingly enough,
			 * even if we do this while the last character is
			 * still being pushed out, they don't hang.  This
			 * seems good enough.
			 */
			while (ISSET(tp->t_state, TS_BUSY)) {
				int error;

				++sc->sc_halt;
				error = ttysleep(tp, &tp->t_outq,
				    TTOPRI | PCATCH, "comprm", 0);
				--sc->sc_halt;
				if (error) {
					splx(s);
					comstart(tp);
					return (error);
				}
			}

			bus_space_write_1(iot, ioh, com_lcr, lcr | LCR_DLAB);
			bus_space_write_1(iot, ioh, com_dlbl, ospeed);
			bus_space_write_1(iot, ioh, com_dlbh, ospeed >> 8);
			bus_space_write_1(iot, ioh, com_lcr, lcr);
			SET(sc->sc_mcr, MCR_DTR);
			bus_space_write_1(iot, ioh, com_mcr, sc->sc_mcr);
		} else
			bus_space_write_1(iot, ioh, com_lcr, lcr);

		if (ISSET(sc->sc_hwflags, COM_HW_FIFO)) {
			u_int8_t fifo = FIFO_ENABLE;
			u_int8_t lcr2;

			switch (sc->sc_uarttype) {
			case COM_UART_ST16650V2:
				if (t->c_ispeed <= 1200)
					fifo |= FIFO_RCV_TRIGGER_8|FIFO_XMT_TRIGGER_8; /* XXX */
				else
					fifo |= FIFO_RCV_TRIGGER_28|FIFO_XMT_TRIGGER_30;
				break;
			case COM_UART_XR16850:
				if (t->c_ispeed <= 1200)
					fifo |= FIFO_RCV3_TRIGGER_8|FIFO_XMT3_TRIGGER_8; /* XXX */
				else
					fifo |= FIFO_RCV3_TRIGGER_60|FIFO_XMT3_TRIGGER_56;
				break;
			case COM_UART_TI16750:
				fifo |= FIFO_ENABLE_64BYTE;
				lcr2 = bus_space_read_1(iot, ioh, com_lcr);
				bus_space_write_1(iot, ioh, com_lcr,
				    lcr2 | LCR_DLAB);
			default:
				if (t->c_ispeed <= 1200)
					fifo |= FIFO_TRIGGER_1;
				else
					fifo |= FIFO_TRIGGER_8;
			}
			bus_space_write_1(iot, ioh, com_fifo, fifo);

			if (sc->sc_uarttype == COM_UART_TI16750)
				bus_space_write_1(iot, ioh, com_lcr, lcr2);
		}
	} else
		bus_space_write_1(iot, ioh, com_lcr, lcr);

	/* When not using CRTSCTS, RTS follows DTR. */
	if (!ISSET(t->c_cflag, CRTSCTS)) {
		if (ISSET(sc->sc_mcr, MCR_DTR)) {
			if (!ISSET(sc->sc_mcr, MCR_RTS)) {
				SET(sc->sc_mcr, MCR_RTS);
				bus_space_write_1(iot, ioh, com_mcr, sc->sc_mcr);
			}
		} else {
			if (ISSET(sc->sc_mcr, MCR_RTS)) {
				CLR(sc->sc_mcr, MCR_RTS);
				bus_space_write_1(iot, ioh, com_mcr, sc->sc_mcr);
			}
		}
		sc->sc_dtr = MCR_DTR | MCR_RTS;
	} else
		sc->sc_dtr = MCR_DTR;

	/* and copy to tty */
	tp->t_ispeed = t->c_ispeed;
	tp->t_ospeed = t->c_ospeed;
	oldcflag = tp->t_cflag;
	tp->t_cflag = t->c_cflag;

	/*
	 * If DCD is off and MDMBUF is changed, ask the tty layer if we should
	 * stop the device.
	 */
	if (!ISSET(sc->sc_msr, MSR_DCD) &&
	    !ISSET(sc->sc_swflags, COM_SW_SOFTCAR) &&
	    ISSET(oldcflag, MDMBUF) != ISSET(tp->t_cflag, MDMBUF) &&
	    (*linesw[tp->t_line].l_modem)(tp, 0) == 0) {
		CLR(sc->sc_mcr, sc->sc_dtr);
		bus_space_write_1(iot, ioh, com_mcr, sc->sc_mcr);
	}

	/* Just to be sure... */
	splx(s);
	comstart(tp);
	return 0;
}

/*
 * (un)block input via hw flowcontrol
 */
int
comhwiflow(tp, block)
	struct tty *tp;
	int block;
{
	struct com_softc *sc = pccom_cd.cd_devs[DEVUNIT(tp->t_dev)];
	bus_space_tag_t iot = sc->sc_iot;
	bus_space_handle_t ioh = sc->sc_ioh;
	int	s;

/*
 * XXX
 * Is spltty needed at all ? sc->sc_mcr is only in comsoft() not comintr()
 */
	s = spltty();
	if (block) {
		/* When not using CRTSCTS, RTS follows DTR. */
		if (ISSET(tp->t_cflag, MDMBUF)) {
			CLR(sc->sc_mcr, (MCR_DTR | MCR_RTS));
			bus_space_write_1(iot, ioh, com_mcr, sc->sc_mcr);
		}
		else {
			CLR(sc->sc_mcr, MCR_RTS);
			bus_space_write_1(iot, ioh, com_mcr, sc->sc_mcr);
		}
	}
	else {
		/* When not using CRTSCTS, RTS follows DTR. */
		if (ISSET(tp->t_cflag, MDMBUF)) {
			SET(sc->sc_mcr, (MCR_DTR | MCR_RTS));
			bus_space_write_1(iot, ioh, com_mcr, sc->sc_mcr);
		}
		else {
			SET(sc->sc_mcr, MCR_RTS);
			bus_space_write_1(iot, ioh, com_mcr, sc->sc_mcr);
		}
	}
	splx(s);
	return 1;
}

void
comstart(tp)
	struct tty *tp;
{
	struct com_softc *sc = pccom_cd.cd_devs[DEVUNIT(tp->t_dev)];
	bus_space_tag_t iot = sc->sc_iot;
	bus_space_handle_t ioh = sc->sc_ioh;
	int s, count;

	s = spltty();
	if (ISSET(tp->t_state, TS_BUSY))
		goto out;
	if (ISSET(tp->t_state, TS_TIMEOUT | TS_TTSTOP) || sc->sc_halt > 0)
		goto stopped;
	if (ISSET(tp->t_cflag, CRTSCTS) && !ISSET(sc->sc_msr, MSR_CTS))
		goto stopped;
	if (tp->t_outq.c_cc <= tp->t_lowat) {
		if (ISSET(tp->t_state, TS_ASLEEP)) {
			CLR(tp->t_state, TS_ASLEEP);
			wakeup((caddr_t)&tp->t_outq);
		}
		selwakeup(&tp->t_wsel);
	}
	count = ndqb(&tp->t_outq, 0);
	splhigh();
	if (count > 0) {
		int n;

		SET(tp->t_state, TS_BUSY);
		if (!ISSET(sc->sc_ier, IER_ETXRDY)) {
			SET(sc->sc_ier, IER_ETXRDY);
			bus_space_write_1(iot, ioh, com_ier, sc->sc_ier);
		}
		n = sc->sc_fifolen;
		if (n > count)
			n = count;
		sc->sc_tba = tp->t_outq.c_cf;
		while (--n >= 0) {
			bus_space_write_1(iot, ioh, com_data, *sc->sc_tba++);
			--count;
		}
		sc->sc_tbc = count;
		goto out;
	}
stopped:
	if (ISSET(sc->sc_ier, IER_ETXRDY)) {
		CLR(sc->sc_ier, IER_ETXRDY);
		bus_space_write_1(iot, ioh, com_ier, sc->sc_ier);
	}
out:
	splx(s);
	return;
}

/*
 * Stop output on a line.
 */
int
comstop(tp, flag)
	struct tty *tp;
	int flag;
{
	int s;
	struct com_softc *sc = pccom_cd.cd_devs[DEVUNIT(tp->t_dev)];

	s = splhigh();
	if (ISSET(tp->t_state, TS_BUSY)) {
		sc->sc_tbc = 0;
		if (!ISSET(tp->t_state, TS_TTSTOP))
			SET(tp->t_state, TS_FLUSH);
	}
	splx(s);
	return 0;
}

void
comdiag(arg)
	void *arg;
{
	struct com_softc *sc = arg;
	int overflows;
	int s;

	s = spltty();
	overflows = sc->sc_overflows;
	sc->sc_overflows = 0;
	splx(s);

	if (overflows)
		log(LOG_WARNING, "%s: %d silo overflow%s\n",
		    sc->sc_dev.dv_xname, overflows, overflows == 1 ? "" : "s");
}

#ifdef PCCOM_DEBUG
int	maxcc = 0;
#endif

void
comsoft()
{
	struct com_softc	*sc;
	struct tty *tp;
	struct linesw	*line;
	int	unit, s, c;
	u_int rxget;
	static int lsrmap[8] = {
		0,      TTY_PE,
		TTY_FE, TTY_PE|TTY_FE,
		TTY_FE, TTY_PE|TTY_FE,
		TTY_FE, TTY_PE|TTY_FE
	};

	for (unit = 0; unit < pccom_cd.cd_ndevs; unit++) {
		sc = pccom_cd.cd_devs[unit];
		if (sc == NULL)
			continue;
		tp = sc->sc_tty;
/*
 * XXX only use (tp == NULL) ???
 */
		if (tp == NULL || !ISSET(tp->t_state, TS_ISOPEN | TS_WOPEN))
			continue;
	 	line = &linesw[tp->t_line];
/*
 * XXX where do we _really_ need spltty(), if at all ???
 */
		s = spltty();
		rxget = sc->sc_rxget;
		while (rxget != sc->sc_rxput) {
			u_int8_t lsr;

			lsr = sc->sc_rxbuf[rxget];
			rxget = (rxget + 1) & RBUFMASK;
			if (ISSET(lsr, LSR_RCV_MASK)) {
				if (ISSET(lsr, LSR_BI)) {
#ifdef DDB
					if (ISSET(sc->sc_hwflags, COM_HW_CONSOLE)) {
						if (db_console)
					 		Debugger();
						rxget = (rxget + 1) & RBUFMASK;
						continue;
 					}
#endif
					c = 0;
				}
				else
					c = sc->sc_rxbuf[rxget];
				if (ISSET(lsr, LSR_OE)) {
					sc->sc_overflows++;
					if (sc->sc_errors++ == 0)
						timeout_add(&sc->sc_diag_tmo, 60 * hz);
				}
				rxget = (rxget + 1) & RBUFMASK;
				c |= lsrmap[(lsr & (LSR_BI|LSR_FE|LSR_PE)) >> 2];
				line->l_rint(c, tp);
			}
			else if (ISSET(lsr, LSR_TXRDY)) {
				CLR(tp->t_state, TS_BUSY);
				if (ISSET(tp->t_state, TS_FLUSH))
					CLR(tp->t_state, TS_FLUSH);
				else
					ndflush(&tp->t_outq,
				 	(int)(sc->sc_tba - tp->t_outq.c_cf));
				if (sc->sc_halt > 0)
					wakeup(&tp->t_outq);
				line->l_start(tp);
			}
			else if (lsr == 0) {
				u_int8_t msr;

				msr = sc->sc_rxbuf[rxget];
				rxget = (rxget + 1) & RBUFMASK;
				if (ISSET(msr, MSR_DDCD) &&
		    		   !ISSET(sc->sc_swflags, COM_SW_SOFTCAR)) {
					if (ISSET(msr, MSR_DCD))
						line->l_modem(tp, 1);
					else if (line->l_modem(tp, 0) == 0) {
						CLR(sc->sc_mcr, sc->sc_dtr);
						bus_space_write_1(sc->sc_iot,
							       sc->sc_ioh,
							       com_mcr,
							       sc->sc_mcr);
					}
				}
				if (ISSET(msr, MSR_DCTS) &&
				    ISSET(msr, MSR_CTS) &&
				    ISSET(tp->t_cflag, CRTSCTS))
					line->l_start(tp);
			}
		}
		sc->sc_rxget = rxget;
/*
 * XXX this is the place where we could unblock the input
 */
		splx(s);
	}
}

#ifdef KGDB

/*
 * If a line break is set, or data matches one of the characters
 * gdb uses to signal a connection, then start up kgdb. Just gobble
 * any other data. Done in a stand alone function because comintr
 * does tty stuff and we don't have one.
 */

int
kgdbintr(arg)
	void *arg;
{
	struct com_softc *sc = arg;
	bus_space_tag_t iot = sc->sc_iot;
	bus_space_handle_t ioh = sc->sc_ioh;
	u_char lsr, data, msr, delta;

	if (!ISSET(sc->sc_hwflags, COM_HW_KGDB))
		return(0);

	for (;;) {
		lsr = bus_space_read_1(iot, ioh, com_lsr);
		if (ISSET(lsr, LSR_RXRDY)) {
			do {
				data = bus_space_read_1(iot, ioh, com_data);
				if (data == 3 || data == '$' || data == '+' ||
				    ISSET(lsr, LSR_BI)) {
					kgdb_connect(1);
					data = 0;
				}
				lsr = bus_space_read_1(iot, ioh, com_lsr);
			} while (ISSET(lsr, LSR_RXRDY));

		}
		if (ISSET(lsr, LSR_BI|LSR_FE|LSR_PE|LSR_OE))
			printf("weird lsr %02x\n", lsr);

		msr = bus_space_read_1(iot, ioh, com_msr);

		if (msr != sc->sc_msr) {
			delta = msr ^ sc->sc_msr;
			sc->sc_msr = msr;
			if (ISSET(delta, MSR_DCD)) {
				if (!ISSET(sc->sc_swflags, COM_SW_SOFTCAR)) {
					CLR(sc->sc_mcr, sc->sc_dtr);
					bus_space_write_1(iot, ioh, com_mcr, sc->sc_mcr);
				}
			}
		}
		if (ISSET(bus_space_read_1(iot, ioh, com_iir), IIR_NOPEND))
			return (1);
	}
}
#endif /* KGDB */

int
comintr(arg)
	void	*arg;
{
	struct com_softc *sc = arg;
	struct tty *tp = sc->sc_tty;
	bus_space_tag_t iot = sc->sc_iot;
	bus_space_handle_t ioh = sc->sc_ioh;
	u_int8_t lsr;
	u_int	rxput;

	if (!sc->sc_tty)
		return (0);	/* can't do squat. */

	if (ISSET(bus_space_read_1(iot, ioh, com_iir), IIR_NOPEND))
		return (0);

	rxput = sc->sc_rxput;
	do {
		u_int8_t msr, delta;

		for (;;) {
			lsr = bus_space_read_1(iot, ioh, com_lsr);
			if (!ISSET(lsr, LSR_RCV_MASK))
				break;
			sc->sc_rxbuf[rxput] = lsr;
			rxput = (rxput + 1) & RBUFMASK;
			sc->sc_rxbuf[rxput] = bus_space_read_1(iot, ioh, com_data);
			rxput = (rxput + 1) & RBUFMASK;
		}
		msr = bus_space_read_1(iot, ioh, com_msr);
		delta = msr ^ sc->sc_msr;

		ttytstamp(tp, sc->sc_msr & MSR_CTS, msr & MSR_CTS,
		    sc->sc_msr & MSR_DCD, msr & MSR_DCD);

		if (!ISSET(delta, MSR_DCD | MSR_CTS | MSR_RI | MSR_DSR))
			continue;
		sc->sc_msr = msr;
/*
 * stop output straight away if CTS drops and RTS/CTS flowcontrol is used
 * XXX what about DTR/DCD flowcontrol (ISSET(t_cflag, MDMBUF))
 */
		msr = (msr & 0xf0) | (delta >> 4);
		if (ISSET(tp->t_cflag, CRTSCTS) && ISSET(msr, MSR_DCTS)) {
			if (!ISSET(msr, MSR_CTS))
				sc->sc_tbc = 0;
		}
		sc->sc_rxbuf[rxput] = 0;
		rxput = (rxput + 1) & RBUFMASK;
		sc->sc_rxbuf[rxput] = msr;
		rxput = (rxput + 1) & RBUFMASK;
	} while (!ISSET(bus_space_read_1(iot, ioh, com_iir), IIR_NOPEND));
	if (ISSET(lsr, LSR_TXRDY)) {
		if (sc->sc_tbc > 0) {
			int	n;

			n = sc->sc_fifolen;
			if (n > sc->sc_tbc)
				n = sc->sc_tbc;
			while (--n >= 0) {
				bus_space_write_1(iot, ioh, com_data, *sc->sc_tba++);
				--sc->sc_tbc;
			}
		}
		else if (ISSET(tp->t_state, TS_BUSY)) {
			sc->sc_rxbuf[rxput] = lsr;
			rxput = (rxput + 1) & RBUFMASK;
		}
	}
	if (sc->sc_rxput != rxput) {
/*
 * XXX
 * This is the place to do input flow control by dropping RTS or DTR.
 * However, 115200 bps transfers get maxcc only up to 112 while there's
 * room for 512 so should we bother ?
 */
#ifdef PCCOM_DEBUG
		int	cc;

		cc = rxput - sc->sc_rxget;
		if (cc < 0)
			cc += RBUFSIZE;
		if (cc > maxcc)
			maxcc = cc;
#endif
		sc->sc_rxput = rxput;
		setsofttty();
	}
	return 1;
}

void
pccom_xr16850_fifo_init(iot, ioh)
	bus_space_tag_t iot;
	bus_space_handle_t ioh;
{
	u_int8_t lcr, efr, fctl;

	lcr = bus_space_read_1(iot, ioh, com_lcr);
	bus_space_write_1(iot, ioh, com_lcr, LCR_EFR);
	efr = bus_space_read_1(iot, ioh, com_efr);
	bus_space_write_1(iot, ioh, com_efr, efr | EFR_ECB);
	fctl = bus_space_read_1(iot, ioh, com_fctl);
	bus_space_write_1(iot, ioh, com_fctl, fctl | FCTL_TRIGGER3);
	bus_space_write_1(iot, ioh, com_lcr, lcr);
}

/*
 * Following are all routines needed for PCCOM to act as console
 */

void
comcnprobe(cp)
	struct consdev *cp;
{
	/* XXX NEEDS TO BE FIXED XXX */
	bus_space_tag_t iot = 0;
	bus_space_handle_t ioh;
	int found;

	if (bus_space_map(iot, CONADDR, COM_NPORTS, 0, &ioh))
		return;
	found = comprobe1(iot, ioh);
	bus_space_unmap(iot, ioh, COM_NPORTS);
	if (!found)
		return;

	/* locate the major number */
	for (commajor = 0; commajor < nchrdev; commajor++)
		if (cdevsw[commajor].d_open == comopen)
			break;

	/* initialize required fields */
	cp->cn_dev = makedev(commajor, CONUNIT);
#if defined(COMCONSOLE) || defined(PCCOMCONSOLE)
	cp->cn_pri = CN_REMOTE;		/* Force a serial port console */
#else
	cp->cn_pri = CN_NORMAL;
#endif
}

/*
 * The following functions are polled getc and putc routines, shared
 * by the console and kgdb glue.
 */

int
com_common_getc(iot, ioh)
	bus_space_tag_t iot;
	bus_space_handle_t ioh;
{
	int s = splhigh();
	u_char stat, c;

	/* block until a character becomes available */
	while (!ISSET(stat = bus_space_read_1(iot, ioh, com_lsr), LSR_RXRDY))
		continue;

	c = bus_space_read_1(iot, ioh, com_data);
	/* clear any interrupts generated by this transmission */
	stat = bus_space_read_1(iot, ioh, com_iir);
	splx(s);
	return (c);
}

void
com_common_putc(iot, ioh, c)
	bus_space_tag_t iot;
	bus_space_handle_t ioh;
	int c;
{
	int s = splhigh();
	int timo;

	/* wait for any pending transmission to finish */
	timo = 150000;
	while (!ISSET(bus_space_read_1(iot, ioh, com_lsr), LSR_TXRDY) && --timo)
		continue;

	bus_space_write_1(iot, ioh, com_data, c);

	/* wait for this transmission to complete */
	timo = 1500000;
	while (!ISSET(bus_space_read_1(iot, ioh, com_lsr), LSR_TXRDY) && --timo)
		continue;

	splx(s);
}

/*
 * Following are all routines needed for COM to act as console
 */

void
comcninit(cp)
	struct consdev *cp;
{

#if 0
	XXX NEEDS TO BE FIXED XXX
	comconsiot = ???;
#endif

#ifdef CONADDR_OVERRIDE
	comconsaddr = CONADDR;
#else
	const int comports[4] = { 0x3f8, 0x2f8, 0x3e8, 0x2e8 };
	int unit = minor(cp->cn_dev);

	if (unit >= 0 && unit < 4)
		comconsaddr = comports[unit];
	else
		comconsaddr = CONADDR;
#endif

	if (bus_space_map(comconsiot, comconsaddr, COM_NPORTS, 0, &comconsioh))
		panic("comcninit: mapping failed");

	cominit(comconsiot, comconsioh, comdefaultrate);
	comconsinit = 0;
}

void
cominit(iot, ioh, rate)
	bus_space_tag_t iot;
	bus_space_handle_t ioh;
	int rate;
{
	int s = splhigh();
	u_int8_t stat;

	bus_space_write_1(iot, ioh, com_lcr, LCR_DLAB);
	rate = comspeed(COM_FREQ, rate); /* XXX not comdefaultrate? */
	bus_space_write_1(iot, ioh, com_dlbl, rate);
	bus_space_write_1(iot, ioh, com_dlbh, rate >> 8);
	bus_space_write_1(iot, ioh, com_lcr, LCR_8BITS);
	bus_space_write_1(iot, ioh, com_mcr, MCR_DTR | MCR_RTS);
	bus_space_write_1(iot, ioh, com_ier, IER_ERXRDY | IER_ETXRDY);
	bus_space_write_1(iot, ioh, com_fifo,
	    FIFO_ENABLE | FIFO_RCV_RST | FIFO_XMT_RST | FIFO_TRIGGER_4);
	stat = bus_space_read_1(iot, ioh, com_iir);
	splx(s);
}

int
comcngetc(dev)
	dev_t dev;
{
	return (com_common_getc(comconsiot, comconsioh));
}

/*
 * Console kernel output character routine.
 */
void
comcnputc(dev, c)
	dev_t dev;
	int c;
{
#if 0
	/* XXX not needed? */
	bus_space_tag_t iot = comconsiot;
	bus_space_handle_t ioh = comconsioh;

	if (comconsinit == 0) {
		cominit(iot, ioh, comdefaultrate);
		comconsinit = 1;
	}
#endif
	com_common_putc(comconsiot, comconsioh, c);
}

void
comcnpollc(dev, on)
	dev_t dev;
	int on;
{

}

#ifdef KGDB
int
com_kgdb_attach(iot, iobase, rate, frequency, cflag)
	bus_space_tag_t iot;
	bus_addr_t iobase;
	int rate, frequency;
	tcflag_t cflag;
{
	if (iot == comconsiot && iobase == comconsaddr) {
		return (EBUSY); /* cannot share with console */
	}

	com_kgdb_iot = iot;
	com_kgdb_addr = iobase;

	if (bus_space_map(com_kgdb_iot, com_kgdb_addr, COM_NPORTS, 0,
	    &com_kgdb_ioh))
		panic("com_kgdb_attach: mapping failed");

	/* XXX We currently don't respect KGDBMODE? */
	cominit(com_kgdb_iot, com_kgdb_ioh, rate);

	kgdb_attach(com_kgdb_getc, com_kgdb_putc, NULL);
	kgdb_dev = 123; /* unneeded, only to satisfy some tests */

	return (0);
}

/* ARGSUSED */
int
com_kgdb_getc(arg)
	void *arg;
{

	return (com_common_getc(com_kgdb_iot, com_kgdb_ioh));
}

/* ARGSUSED */
void
com_kgdb_putc(arg, c)
	void *arg;
	int c;
{

	return (com_common_putc(com_kgdb_iot, com_kgdb_ioh, c));
}
#endif /* KGDB */