1) Set ipending back to 4, because (16 + 4) bit not in

	netmask or impmask.

2) Fixes from Bruce:
	o Changed name of schedsoftcom() to setsofttty() to match
	  setsoftclock()
	o Bool_t isn't used.
	o tx_fifo_size is 1 for chips without fifos, 16 for 16550's, to
	  help to output more efficiently for 16550's (LSR_TXRDY means
	  that the fifo is empty, not that it has space for one char).
	o Changed name of softsio1() to siopoll() and merged compoll()
	  into siopoll().
	o The probe forgot to clear com_mcr after it failed.  This is
	  harmful for 4 single serial ports on 2 interrupts.  It makes
	  partial misconfigurations worse.
	o Don't bother initializing static variables that are 0 (bidir
	  stuff).
	o Only initialize t_oflag to TTYDEF_OFLAG if unit == COMCONSOLE,
	  not if COMCONSOLE is defined.
	o Don't call siointr() from comparam() if there is no output in
	  progress.  For the call from sioopen(), there's no output in
	  progress, and siointr() often saw silo overflows for stale
	  input because it was called before sioopen() discarded the
	  input.
	o Let ttselect() do the work for select(), so that the fixes for
	  ttselect() don't have to be duplicated in zillions of drivers.

3 files changed, 273 insertions, 453 deletions

diff --git a/sys/dev/sio/sio.c b/sys/dev/sio/sio.c
index 21c9f90..30c9768 100644
--- a/sys/dev/sio/sio.c
+++ b/sys/dev/sio/sio.c
@@ -31,7 +31,7 @@
  * SUCH DAMAGE.
  *
  *	from: @(#)com.c	7.5 (Berkeley) 5/16/91
- *	$Id: sio.c,v 1.22 1994/01/11 18:31:45 ache Exp $
+ *	$Id: sio.c,v 1.23 1994/01/31 06:12:18 davidg Exp $
  */
 
 #include "sio.h"
@@ -71,7 +71,7 @@
 #define	UNIT(x)		(minor(x))	/* XXX */
 #else /* COM_BIDIR */
 #define COM_UNITMASK    0x7f
-#define COM_CALLOUTMASK 0x80
+#define COM_CALLOUTMASK 0x80		/* for both minor and dev */
 #define UNIT(x)         (minor(x) & COM_UNITMASK)
 #define CALLOUT(x)      (minor(x) & COM_CALLOUTMASK)
 #endif /* COM_BIDIR */
@@ -98,7 +98,7 @@
 #endif
 
 #define	com_scr		7	/* scratch register for 16450-16550 (R/W) */
-#define	schedsoftcom()	(ipending |= 1 << (16 + 4))	/* XXX */
+#define setsofttty()    (ipending |= 1 << 4)     /* XXX */
 
 /*
  * Input buffer watermarks.
@@ -148,7 +148,6 @@ static	char	*error_desc[] = {
 
 /* types.  XXX - should be elsewhere */
 typedef u_int	Port_t;		/* hardware port */
-typedef int	Bool_t;		/* promoted boolean */
 typedef u_char	bool_t;		/* boolean */
 
 /* com device structure */
@@ -167,6 +166,7 @@ struct com_s {
 	bool_t	multiport;	/* is this unit part of a multiport device? */
 #endif /* COM_MULTIPORT */
 	int	dtr_wait;	/* time to hold DTR down on close (* 1/HZ) */
+	u_int	tx_fifo_size;
 
 	/*
 	 * The high level of the driver never reads status registers directly
@@ -228,6 +228,7 @@ void	siocnprobe	__P((struct consdev *cp));
 void	siocnputc	__P((Dev_t dev, int c));
 int	sioopen		__P((Dev_t dev, int oflags, int devtype,
 			     struct proc *p));
+void	siopoll		__P((void));
 int	sioread		__P((Dev_t dev, struct uio *uio, int ioflag));
 int	sioselect	__P((Dev_t dev, int rw, struct proc *p));
 void	siostop		__P((struct tty *tp, int rw));
@@ -239,12 +240,11 @@ static	void	comflush	__P((struct com_s *com));
 static	void	comhardclose	__P((struct com_s *com));
 static	void	cominit		__P((int unit, int rate));
 #ifdef COM_MULTIPORT
-static  bool_t  comintr1        __P((struct com_s *com));
+static	void	comintr1	__P((struct com_s *com));
 #endif /* COM_MULTIPORT */
 static	void	commctl		__P((struct com_s *com, int bits, int how));
 static	int	comparam	__P((struct tty *tp, struct termios *t));
 static	int	sioprobe	__P((struct isa_device *dev));
-static	void	compoll		__P((void));
 static  void    comstart        __P((struct tty *tp));
 static  void    comwakeup       __P((caddr_t chan, int ticks));
 static	int	tiocm_xxx2mcr	__P((int tiocm_xxx));
@@ -386,12 +386,14 @@ sioprobe(dev)
 	    || isa_irq_pending(dev)
 	    || (inb(iobase + com_iir) & IIR_IMASK) != IIR_NOPEND)
 		result = 0;
+	if (result == 0)
+		outb(iobase + com_mcr, 0);
 
 	enable_intr();
 	return (result);
 }
 
-static int			/* XXX - should be void */
+static int
 sioattach(isdp)
 	struct isa_device	*isdp;
 {
@@ -423,6 +425,7 @@ sioattach(isdp)
 	com->cfcr_image = CFCR_8BITS;
 	com->mcr_image = MCR_IENABLE;
 	com->dtr_wait = 200;
+	com->tx_fifo_size = 1;
 	com->iptr = com->ibuf = com->ibuf1;
 	com->ibufend = com->ibuf1 + RS_IBUFSIZE;
 	com->ihighwater = com->ibuf1 + RS_IHIGHWATER;
@@ -433,14 +436,6 @@ sioattach(isdp)
 	com->line_status_port = iobase + com_lsr;
 	com->modem_status_port = iobase + com_msr;
 	com->tp = &sio_tty[unit];
-#ifdef COM_BIDIR
-	/*
-	 * if bidirectional ports possible, clear the bidir port info;
-	 */
-	com->bidir = FALSE;
-	com->active = FALSE;
-	com->active_in = com->active_out = FALSE;
-#endif /* COM_BIDIR */
 
 	/* attempt to determine UART type */
 	printf("sio%d: type", unit);
@@ -481,6 +476,7 @@ sioattach(isdp)
 			printf(" fifo software disabled");
 		} else {
 			com->hasfifo = TRUE;
+			com->tx_fifo_size = 16;
 		}
 		break;
 	}
@@ -503,8 +499,7 @@ determined_type: ;
 		masterdev = find_isadev(isa_devtab_tty, &siodriver,
 					COM_MPMASTER(isdp));
 		outb(masterdev->id_iobase + com_scr, 0x80);
-	}
-	else
+	} else
 		com->multiport = FALSE;
 #endif /* COM_MULTIPORT */
 	printf("\n");
@@ -522,8 +517,7 @@ determined_type: ;
 				 */
 				printf("sio%d: ", unit);
 				kgdb_connect(1);
-			}
-			else
+			} else
 				printf("sio%d: kgdb enabled\n", unit);
 		}
 	}
@@ -667,10 +661,10 @@ bidir_open_top:
 			 * can be turned off.
 			 */
 			tp->t_iflag = 0;
+			tp->t_oflag = 0;
 #ifdef COMCONSOLE
+			if (unit == comconsole)
 			tp->t_oflag = TTYDEF_OFLAG;
-#else
-			tp->t_oflag = 0;
 #endif
 			tp->t_cflag = CREAD | CS8 | HUPCL;
 			tp->t_lflag = 0;
@@ -695,22 +689,6 @@ bidir_open_top:
 		if (error != 0)
 			goto out;
 		ttsetwater(tp);
-
-		/*
-		 * XXX temporary fix for deadlock in ttywait().
-		 *
-		 * If two processes wait for output to drain from the same
-		 * tty, and the amount of output to drain is > 0 and
-		 * <= tp->t_lowat, then the processes will take turns
-		 * uselessly waking each other up until the output drains,
-		 * with cpl higher than spltty() throughout.
-		 *
-		 * The sleep address and TS_ASLEEP flag ought to be different
-		 * for the different events (output done) and (output almost
-		 * done).
-		 */
-		tp->t_lowat = 0;
-
 		iobase = com->iobase;
 		if (com->hasfifo) {
 			/* (re)enable and drain FIFO */
@@ -728,8 +706,7 @@ bidir_open_top:
 		enable_intr();
 		if (com->prev_modem_status & MSR_DCD || FAKE_DCD(unit))
 			tp->t_state |= TS_CARR_ON;
-	}
-	else if (tp->t_state & TS_XCLUDE && p->p_ucred->cr_uid != 0) {
+	} else if (tp->t_state & TS_XCLUDE && p->p_ucred->cr_uid != 0) {
 		splx(s);
 		return (EBUSY);
 	}
@@ -799,18 +776,21 @@ comhardclose(com)
 	Port_t		iobase;
 	int		s;
 	struct tty	*tp;
+	int		unit;
 
 	s = spltty();
 	iobase = com->iobase;
 	outb(iobase + com_cfcr, com->cfcr_image &= ~CFCR_SBREAK);
+	unit = com - &com_structs[0];
 #ifdef KGDB
 	/* do not disable interrupts or hang up if debugging */
-	if (kgdb_dev != makedev(commajor, com - &com_structs[0]))
+	if (kgdb_dev != makedev(commajor, unit))
 #endif
 	{
 		outb(iobase + com_ier, 0);
 		tp = com->tp;
 		if (tp->t_cflag & HUPCL || tp->t_state & TS_WOPEN
+		    || !(com->prev_modem_status & MSR_DCD) && !FAKE_DCD(unit)
 		    || !(tp->t_state & TS_ISOPEN)) {
 			commctl(com, MCR_RTS, DMSET);
 			if (com->dtr_wait != 0)
@@ -887,30 +867,28 @@ siointr(unit)
 	 * If the IRQ signal is just an OR of the IRQ signals from several
 	 * devices, then the edge from one may be lost because another is
 	 * on.
-	 *
-	 * XXX getting the status from comintr1() is not best and may be
-	 * incorrect.  It would be better to test the int_id's in a tight
-	 * loop.  If each is off when it is tested, then they all must
-	 * have been off at the start.
 	 */
 	do {
 		possibly_more_intrs = FALSE;
 		for (unit = 0; unit < NSIO; ++unit) {
 			com = com_addr(unit);
-			if (com != NULL) {
+			if (com != NULL
+			    && (inb(com->int_id_port) & IIR_IMASK)
+			       != IIR_NOPEND) {
 				/*
 				 * XXX call comintr1() instead of here from
 				 * comwakeup().  The interrupt edge problem
 				 * only exists for real interrupts.
 				 */
-				possibly_more_intrs |= comintr1(com);
+				comintr1(com);
+				possibly_more_intrs = TRUE;
 			}
 		}
 	} while (possibly_more_intrs);
 	return;
 }
 
-static bool_t
+static void
 comintr1(com)
 	struct com_s *com;
 {
@@ -918,9 +896,6 @@ comintr1(com)
 	u_char		modem_status;
 	u_char		*ioptr;
 	u_char		recv_data;
-	bool_t		donesomething;
-
-	donesomething = FALSE;
 #endif /* COM_MULTIPORT */
 
 	while (TRUE) {
@@ -929,9 +904,6 @@ comintr1(com)
 		/* input event? (check first to help avoid overruns) */
 		while (line_status & LSR_RCV_MASK) {
 			/* break/unnattached error bits or real input? */
-#ifdef COM_MULTIPORT
-			donesomething = TRUE;
-#endif /* COM_MULTIPORT */
 			if (!(line_status & LSR_RXRDY))
 				recv_data = 0;
 			else
@@ -951,9 +923,9 @@ comintr1(com)
 				CE_RECORD(com, CE_INTERRUPT_BUF_OVERFLOW);
 			else {
 				++com_events;
-#if 0
+#if 0 /* for testing input latency vs efficiency */
 if (com->iptr - com->ibuf == 8)
-	schedsoftcom();
+	setsofttty();
 #endif
 				ioptr[0] = recv_data;
 				ioptr[CE_INPUT_OFFSET] = line_status;
@@ -983,14 +955,11 @@ if (com->iptr - com->ibuf == 8)
 			 * UARTs mess them up, and it's easy to remember the
 			 * previous bits and calculate the delta.
 			 */
-#ifdef COM_MULTIPORT
-			donesomething = TRUE;
-#endif /* COM_MULTIPORT */
 			com->last_modem_status = modem_status;
 			if (!(com->state & CS_CHECKMSR)) {
 				com_events += LOTS_OF_EVENTS;
 				com->state |= CS_CHECKMSR;
-				schedsoftcom();
+				setsofttty();
 			}
 
 			/* handle CTS change immediately for crisp flow ctl */
@@ -1005,28 +974,35 @@ if (com->iptr - com->ibuf == 8)
 		/* output queued and everything ready? */
 		if (line_status & LSR_TXRDY
 		    && com->state >= (CS_ODEVREADY | CS_BUSY | CS_TTGO)) {
-#ifdef COM_MULTIPORT
-			donesomething = TRUE;
-#endif /* COM_MULTIPORT */
 			ioptr = com->optr;
-			outb(com->data_port, *ioptr);
+			if (com->tx_fifo_size > 1) {
+				u_int	ocount;
+
+				ocount = com->obufend - ioptr;
+				if (ocount > com->tx_fifo_size)
+					ocount = com->tx_fifo_size;
+				com->bytes_out += ocount;
+				do
+					outb(com->data_port, *ioptr++);
+				while (--ocount != 0);
+			} else {
+				outb(com->data_port, *ioptr++);
 			++com->bytes_out;
-			com->optr = ++ioptr;
+			}
+			com->optr = ioptr;
 			if (ioptr >= com->obufend) {
 				/* output just completed */
 				com_events += LOTS_OF_EVENTS;
 				com->state ^= (CS_ODONE | CS_BUSY);
-				schedsoftcom();	/* handle at high level ASAP */
+				setsofttty();	/* handle at high level ASAP */
 			}
 		}
 
 		/* finished? */
+#ifndef COM_MULTIPORT
 		if ((inb(com->int_id_port) & IIR_IMASK) == IIR_NOPEND)
-#ifdef COM_MULTIPORT
-			return (donesomething);
-#else
-			return;
 #endif /* COM_MULTIPORT */
+			return;
 	}
 }
 
@@ -1063,21 +1039,19 @@ sioioctl(dev, cmd, data, flag, p)
 
 	com = com_addr(UNIT(dev));
 	tp = com->tp;
-
 	error = (*linesw[tp->t_line].l_ioctl)(tp, cmd, data, flag);
 	if (error >= 0)
 		return (error);
 	error = ttioctl(tp, cmd, data, flag);
-#ifdef COM_BIDIR
-	/* XXX: plug security hole while stucky bits not yet implemented */
 
+#ifdef COM_BIDIR
+	/* XXX: plug security hole while sticky bits not yet implemented */
 	if (com->bidir && com->active_in && p->p_ucred->cr_uid != 0)
 		tp->t_cflag &= ~CLOCAL;
 #endif
-	if (error >= 0) {
-		tp->t_lowat = 0;	/* XXX part of ttywait() deadlock fix */
+
+	if (error >= 0)
 		return (error);
-	}
 
 	iobase = com->iobase;
 	s = spltty();
@@ -1204,11 +1178,10 @@ comflush(com)
 	com->tp->t_state &= ~TS_BUSY;
 }
 
-static void
-compoll()
+void
+siopoll()
 {
 	static bool_t	awake = FALSE;
-	struct com_s	*com;
 	int		s;
 	int		unit;
 
@@ -1225,6 +1198,7 @@ compoll()
 repeat:
 	for (unit = 0; unit < NSIO; ++unit) {
 		u_char          *buf;
+		struct com_s    *com;
 		u_char		*ibuf;
 		int		incc;
 		struct tty	*tp;
@@ -1234,11 +1208,11 @@ repeat:
 			continue;
 		tp = com->tp;
 
-		buf = NULL;     /* avoid compiler warning */
 		/* switch the role of the low-level input buffers */
-		if (com->iptr == (ibuf = com->ibuf))
+		if (com->iptr == (ibuf = com->ibuf)) {
+			buf = NULL;     /* not used, but compiler can't tell */
 			incc = 0;
-		else {
+		} else {
 			buf = ibuf;
 			disable_intr();
 			incc = com->iptr - buf;
@@ -1280,8 +1254,7 @@ repeat:
 #ifdef COM_BIDIR
 					wakeup((caddr_t) &com->active_in);
 #endif /* COM_BIDIR */
-				}
-				else
+				} else
 					(*linesw[tp->t_line].l_modem)(tp, 0);
 			}
 		}
@@ -1289,18 +1262,14 @@ repeat:
 		/* XXX */
 		if (TRUE) {
 			u_int delta;
-			u_int delta_error_counts[CE_NTYPES];
 			int errnum;
 			u_long total;
 
+			for (errnum = 0; errnum < CE_NTYPES; ++errnum) {
 			disable_intr();
-			bcopy(com->delta_error_counts, delta_error_counts,
-			      sizeof delta_error_counts);
-			bzero(com->delta_error_counts,
-			      sizeof delta_error_counts);
+				delta = com->delta_error_counts[errnum];
+				com->delta_error_counts[errnum] = 0;
 			enable_intr();
-			for (errnum = 0; errnum < CE_NTYPES; ++errnum) {
-				delta = delta_error_counts[errnum];
 				if (delta != 0) {
 					total =
 					com->error_counts[errnum] += delta;
@@ -1359,8 +1328,7 @@ repeat:
 				tp->t_lflag &= ~FLUSHO;
 				ttstart(tp);
 			}
-		}
-		else {
+		} else {
 			do {
 				u_char	line_status;
 				int	recv_data;
@@ -1474,9 +1442,9 @@ retry:
 
 	/*
 	 * XXX - clearing CS_TTGO is not sufficient to stop further output,
-	 * because compoll() calls comstart() which set it again because
-	 * TS_TTSTOP is set.  Clearing TS_TTSTOP would not be sufficient,
-	 * for similar reasons.
+	 * because siopoll() calls comstart() which usually sets it again
+	 * because TS_TTSTOP is clear.  Setting TS_TTSTOP would not be
+	 * sufficient, for similar reasons.
 	 */
 	if ((inb(com->line_status_port) & (LSR_TSRE | LSR_TXRDY))
 	       != (LSR_TSRE | LSR_TXRDY))
@@ -1508,7 +1476,17 @@ retry:
 			com->state &= ~CS_ODEVREADY;
 	}
 
-	siointr(unit);		/* recover from fiddling with CS_TTGO */
+	/*
+	 * Recover from fiddling with CS_TTGO.  We used to call siointr()
+	 * unconditionally, but that defeated the careful discarding of
+	 * stale input in sioopen().
+	 *
+	 * XXX sioopen() is not careful waiting for carrier for the callout
+	 * case.
+	 */
+	if (com->state >= (CS_BUSY | CS_TTGO))
+		siointr(unit);
+
 	enable_intr();
 	splx(s);
 	return (0);
@@ -1533,8 +1511,7 @@ comstart(tp)
 	if (tp->t_state & TS_RTS_IFLOW) {
 		if (com->mcr_image & MCR_RTS && com->state & CS_RTS_IFLOW)
 			outb(com->modem_ctl_port, com->mcr_image &= ~MCR_RTS);
-	}
-	else {
+	} else {
 		if (!(com->mcr_image & MCR_RTS) && com->iptr < com->ihighwater)
 			outb(com->modem_ctl_port, com->mcr_image |= MCR_RTS);
 	}
@@ -1556,8 +1533,7 @@ comstart(tp)
 		disable_intr();
 		siointr(unit);
 		enable_intr();
-	}
-	else if (RB_LEN(&tp->t_out) != 0) {
+	} else if (RB_LEN(&tp->t_out) != 0) {
 		tp->t_state |= TS_BUSY;
 		com->ocount = RB_CONTIGGET(&tp->t_out);
 		disable_intr();
@@ -1593,6 +1569,15 @@ siostop(tp, rw)
 	enable_intr();
 }
 
+int
+sioselect(dev, rw, p)
+	dev_t		dev;
+	int		rw;
+	struct proc	*p;
+{
+	return ttselect(dev & ~COM_CALLOUTMASK, rw, p);
+}
+
 static void
 commctl(com, bits, how)
 	struct com_s	*com;
@@ -1620,16 +1605,17 @@ comwakeup(chan, ticks)
 	caddr_t chan;
 	int ticks;
 {
-	struct com_s	*com;
 	int		unit;
 
 	timeout(comwakeup, (caddr_t) NULL, hz / 100);
 	if (com_events != 0)
-		/* schedule compoll() to run when the cpl allows */
-		schedsoftcom();
+		/* schedule siopoll() to run when the cpl allows */
+		setsofttty();
 
 	/* recover from lost output interrupts */
 	for (unit = 0; unit < NSIO; ++unit) {
+		struct com_s	*com;
+
 		com = com_addr(unit);
 		if (com != NULL && com->state >= (CS_BUSY | CS_TTGO)) {
 			disable_intr();
@@ -1643,7 +1629,7 @@ comwakeup(chan, ticks)
 void
 softsio1()
 {
-	compoll();
+	siopoll();
 }
 
 /*
@@ -1674,7 +1660,6 @@ siocnprobe(cp)
 
 	/* initialize required fields */
 	cp->cn_dev = makedev(commajor, unit);
-	cp->cn_tp = &sio_tty[unit];
 #ifdef	COMCONSOLE
 	cp->cn_pri = CN_REMOTE;		/* Force a serial port console */
 #else
@@ -1775,49 +1760,4 @@ siocnputc(dev, c)
 	splx(s);
 }
 
-/*
- * XXX - sioselect() is almost a copy of ttselect().  It is required because
- * ttselect() can't determine the tty struct because stuff is encoded in the
- * high bit of the minor number.
- */
-int
-sioselect(dev, rw, p)
-	dev_t dev;
-	int rw;
-	struct proc *p;
-{
-	struct tty *tp = &sio_tty[UNIT(dev)];
-	int nread;
-	int s = spltty();
-        struct proc *selp;
-
-	switch (rw) {
-
-	case FREAD:
-		nread = ttnread(tp);
-		if (nread > 0 ||
-		   ((tp->t_cflag&CLOCAL) == 0 && (tp->t_state&TS_CARR_ON) == 0))
-			goto win;
-		if (tp->t_rsel && (selp = pfind(tp->t_rsel)) && selp->p_wchan == (caddr_t)&selwait)
-			tp->t_state |= TS_RCOLL;
-		else
-			tp->t_rsel = p->p_pid;
-		break;
-
-	case FWRITE:
-		if (RB_LEN(&tp->t_out) <= tp->t_lowat)
-			goto win;
-		if (tp->t_wsel && (selp = pfind(tp->t_wsel)) && selp->p_wchan == (caddr_t)&selwait)
-			tp->t_state |= TS_WCOLL;
-		else
-			tp->t_wsel = p->p_pid;
-		break;
-	}
-	splx(s);
-	return (0);
-  win:
-	splx(s);
-	return (1);
-}
-
 #endif /* NSIO > 0 */
diff --git a/sys/i386/isa/sio.c b/sys/i386/isa/sio.c
index 21c9f90..30c9768 100644
--- a/sys/i386/isa/sio.c
+++ b/sys/i386/isa/sio.c
@@ -31,7 +31,7 @@
  * SUCH DAMAGE.
  *
  *	from: @(#)com.c	7.5 (Berkeley) 5/16/91
- *	$Id: sio.c,v 1.22 1994/01/11 18:31:45 ache Exp $
+ *	$Id: sio.c,v 1.23 1994/01/31 06:12:18 davidg Exp $
  */
 
 #include "sio.h"
@@ -71,7 +71,7 @@
 #define	UNIT(x)		(minor(x))	/* XXX */
 #else /* COM_BIDIR */
 #define COM_UNITMASK    0x7f
-#define COM_CALLOUTMASK 0x80
+#define COM_CALLOUTMASK 0x80		/* for both minor and dev */
 #define UNIT(x)         (minor(x) & COM_UNITMASK)
 #define CALLOUT(x)      (minor(x) & COM_CALLOUTMASK)
 #endif /* COM_BIDIR */
@@ -98,7 +98,7 @@
 #endif
 
 #define	com_scr		7	/* scratch register for 16450-16550 (R/W) */
-#define	schedsoftcom()	(ipending |= 1 << (16 + 4))	/* XXX */
+#define setsofttty()    (ipending |= 1 << 4)     /* XXX */
 
 /*
  * Input buffer watermarks.
@@ -148,7 +148,6 @@ static	char	*error_desc[] = {
 
 /* types.  XXX - should be elsewhere */
 typedef u_int	Port_t;		/* hardware port */
-typedef int	Bool_t;		/* promoted boolean */
 typedef u_char	bool_t;		/* boolean */
 
 /* com device structure */
@@ -167,6 +166,7 @@ struct com_s {
 	bool_t	multiport;	/* is this unit part of a multiport device? */
 #endif /* COM_MULTIPORT */
 	int	dtr_wait;	/* time to hold DTR down on close (* 1/HZ) */
+	u_int	tx_fifo_size;
 
 	/*
 	 * The high level of the driver never reads status registers directly
@@ -228,6 +228,7 @@ void	siocnprobe	__P((struct consdev *cp));
 void	siocnputc	__P((Dev_t dev, int c));
 int	sioopen		__P((Dev_t dev, int oflags, int devtype,
 			     struct proc *p));
+void	siopoll		__P((void));
 int	sioread		__P((Dev_t dev, struct uio *uio, int ioflag));
 int	sioselect	__P((Dev_t dev, int rw, struct proc *p));
 void	siostop		__P((struct tty *tp, int rw));
@@ -239,12 +240,11 @@ static	void	comflush	__P((struct com_s *com));
 static	void	comhardclose	__P((struct com_s *com));
 static	void	cominit		__P((int unit, int rate));
 #ifdef COM_MULTIPORT
-static  bool_t  comintr1        __P((struct com_s *com));
+static	void	comintr1	__P((struct com_s *com));
 #endif /* COM_MULTIPORT */
 static	void	commctl		__P((struct com_s *com, int bits, int how));
 static	int	comparam	__P((struct tty *tp, struct termios *t));
 static	int	sioprobe	__P((struct isa_device *dev));
-static	void	compoll		__P((void));
 static  void    comstart        __P((struct tty *tp));
 static  void    comwakeup       __P((caddr_t chan, int ticks));
 static	int	tiocm_xxx2mcr	__P((int tiocm_xxx));
@@ -386,12 +386,14 @@ sioprobe(dev)
 	    || isa_irq_pending(dev)
 	    || (inb(iobase + com_iir) & IIR_IMASK) != IIR_NOPEND)
 		result = 0;
+	if (result == 0)
+		outb(iobase + com_mcr, 0);
 
 	enable_intr();
 	return (result);
 }
 
-static int			/* XXX - should be void */
+static int
 sioattach(isdp)
 	struct isa_device	*isdp;
 {
@@ -423,6 +425,7 @@ sioattach(isdp)
 	com->cfcr_image = CFCR_8BITS;
 	com->mcr_image = MCR_IENABLE;
 	com->dtr_wait = 200;
+	com->tx_fifo_size = 1;
 	com->iptr = com->ibuf = com->ibuf1;
 	com->ibufend = com->ibuf1 + RS_IBUFSIZE;
 	com->ihighwater = com->ibuf1 + RS_IHIGHWATER;
@@ -433,14 +436,6 @@ sioattach(isdp)
 	com->line_status_port = iobase + com_lsr;
 	com->modem_status_port = iobase + com_msr;
 	com->tp = &sio_tty[unit];
-#ifdef COM_BIDIR
-	/*
-	 * if bidirectional ports possible, clear the bidir port info;
-	 */
-	com->bidir = FALSE;
-	com->active = FALSE;
-	com->active_in = com->active_out = FALSE;
-#endif /* COM_BIDIR */
 
 	/* attempt to determine UART type */
 	printf("sio%d: type", unit);
@@ -481,6 +476,7 @@ sioattach(isdp)
 			printf(" fifo software disabled");
 		} else {
 			com->hasfifo = TRUE;
+			com->tx_fifo_size = 16;
 		}
 		break;
 	}
@@ -503,8 +499,7 @@ determined_type: ;
 		masterdev = find_isadev(isa_devtab_tty, &siodriver,
 					COM_MPMASTER(isdp));
 		outb(masterdev->id_iobase + com_scr, 0x80);
-	}
-	else
+	} else
 		com->multiport = FALSE;
 #endif /* COM_MULTIPORT */
 	printf("\n");
@@ -522,8 +517,7 @@ determined_type: ;
 				 */
 				printf("sio%d: ", unit);
 				kgdb_connect(1);
-			}
-			else
+			} else
 				printf("sio%d: kgdb enabled\n", unit);
 		}
 	}
@@ -667,10 +661,10 @@ bidir_open_top:
 			 * can be turned off.
 			 */
 			tp->t_iflag = 0;
+			tp->t_oflag = 0;
 #ifdef COMCONSOLE
+			if (unit == comconsole)
 			tp->t_oflag = TTYDEF_OFLAG;
-#else
-			tp->t_oflag = 0;
 #endif
 			tp->t_cflag = CREAD | CS8 | HUPCL;
 			tp->t_lflag = 0;
@@ -695,22 +689,6 @@ bidir_open_top:
 		if (error != 0)
 			goto out;
 		ttsetwater(tp);
-
-		/*
-		 * XXX temporary fix for deadlock in ttywait().
-		 *
-		 * If two processes wait for output to drain from the same
-		 * tty, and the amount of output to drain is > 0 and
-		 * <= tp->t_lowat, then the processes will take turns
-		 * uselessly waking each other up until the output drains,
-		 * with cpl higher than spltty() throughout.
-		 *
-		 * The sleep address and TS_ASLEEP flag ought to be different
-		 * for the different events (output done) and (output almost
-		 * done).
-		 */
-		tp->t_lowat = 0;
-
 		iobase = com->iobase;
 		if (com->hasfifo) {
 			/* (re)enable and drain FIFO */
@@ -728,8 +706,7 @@ bidir_open_top:
 		enable_intr();
 		if (com->prev_modem_status & MSR_DCD || FAKE_DCD(unit))
 			tp->t_state |= TS_CARR_ON;
-	}
-	else if (tp->t_state & TS_XCLUDE && p->p_ucred->cr_uid != 0) {
+	} else if (tp->t_state & TS_XCLUDE && p->p_ucred->cr_uid != 0) {
 		splx(s);
 		return (EBUSY);
 	}
@@ -799,18 +776,21 @@ comhardclose(com)
 	Port_t		iobase;
 	int		s;
 	struct tty	*tp;
+	int		unit;
 
 	s = spltty();
 	iobase = com->iobase;
 	outb(iobase + com_cfcr, com->cfcr_image &= ~CFCR_SBREAK);
+	unit = com - &com_structs[0];
 #ifdef KGDB
 	/* do not disable interrupts or hang up if debugging */
-	if (kgdb_dev != makedev(commajor, com - &com_structs[0]))
+	if (kgdb_dev != makedev(commajor, unit))
 #endif
 	{
 		outb(iobase + com_ier, 0);
 		tp = com->tp;
 		if (tp->t_cflag & HUPCL || tp->t_state & TS_WOPEN
+		    || !(com->prev_modem_status & MSR_DCD) && !FAKE_DCD(unit)
 		    || !(tp->t_state & TS_ISOPEN)) {
 			commctl(com, MCR_RTS, DMSET);
 			if (com->dtr_wait != 0)
@@ -887,30 +867,28 @@ siointr(unit)
 	 * If the IRQ signal is just an OR of the IRQ signals from several
 	 * devices, then the edge from one may be lost because another is
 	 * on.
-	 *
-	 * XXX getting the status from comintr1() is not best and may be
-	 * incorrect.  It would be better to test the int_id's in a tight
-	 * loop.  If each is off when it is tested, then they all must
-	 * have been off at the start.
 	 */
 	do {
 		possibly_more_intrs = FALSE;
 		for (unit = 0; unit < NSIO; ++unit) {
 			com = com_addr(unit);
-			if (com != NULL) {
+			if (com != NULL
+			    && (inb(com->int_id_port) & IIR_IMASK)
+			       != IIR_NOPEND) {
 				/*
 				 * XXX call comintr1() instead of here from
 				 * comwakeup().  The interrupt edge problem
 				 * only exists for real interrupts.
 				 */
-				possibly_more_intrs |= comintr1(com);
+				comintr1(com);
+				possibly_more_intrs = TRUE;
 			}
 		}
 	} while (possibly_more_intrs);
 	return;
 }
 
-static bool_t
+static void
 comintr1(com)
 	struct com_s *com;
 {
@@ -918,9 +896,6 @@ comintr1(com)
 	u_char		modem_status;
 	u_char		*ioptr;
 	u_char		recv_data;
-	bool_t		donesomething;
-
-	donesomething = FALSE;
 #endif /* COM_MULTIPORT */
 
 	while (TRUE) {
@@ -929,9 +904,6 @@ comintr1(com)
 		/* input event? (check first to help avoid overruns) */
 		while (line_status & LSR_RCV_MASK) {
 			/* break/unnattached error bits or real input? */
-#ifdef COM_MULTIPORT
-			donesomething = TRUE;
-#endif /* COM_MULTIPORT */
 			if (!(line_status & LSR_RXRDY))
 				recv_data = 0;
 			else
@@ -951,9 +923,9 @@ comintr1(com)
 				CE_RECORD(com, CE_INTERRUPT_BUF_OVERFLOW);
 			else {
 				++com_events;
-#if 0
+#if 0 /* for testing input latency vs efficiency */
 if (com->iptr - com->ibuf == 8)
-	schedsoftcom();
+	setsofttty();
 #endif
 				ioptr[0] = recv_data;
 				ioptr[CE_INPUT_OFFSET] = line_status;
@@ -983,14 +955,11 @@ if (com->iptr - com->ibuf == 8)
 			 * UARTs mess them up, and it's easy to remember the
 			 * previous bits and calculate the delta.
 			 */
-#ifdef COM_MULTIPORT
-			donesomething = TRUE;
-#endif /* COM_MULTIPORT */
 			com->last_modem_status = modem_status;
 			if (!(com->state & CS_CHECKMSR)) {
 				com_events += LOTS_OF_EVENTS;
 				com->state |= CS_CHECKMSR;
-				schedsoftcom();
+				setsofttty();
 			}
 
 			/* handle CTS change immediately for crisp flow ctl */
@@ -1005,28 +974,35 @@ if (com->iptr - com->ibuf == 8)
 		/* output queued and everything ready? */
 		if (line_status & LSR_TXRDY
 		    && com->state >= (CS_ODEVREADY | CS_BUSY | CS_TTGO)) {
-#ifdef COM_MULTIPORT
-			donesomething = TRUE;
-#endif /* COM_MULTIPORT */
 			ioptr = com->optr;
-			outb(com->data_port, *ioptr);
+			if (com->tx_fifo_size > 1) {
+				u_int	ocount;
+
+				ocount = com->obufend - ioptr;
+				if (ocount > com->tx_fifo_size)
+					ocount = com->tx_fifo_size;
+				com->bytes_out += ocount;
+				do
+					outb(com->data_port, *ioptr++);
+				while (--ocount != 0);
+			} else {
+				outb(com->data_port, *ioptr++);
 			++com->bytes_out;
-			com->optr = ++ioptr;
+			}
+			com->optr = ioptr;
 			if (ioptr >= com->obufend) {
 				/* output just completed */
 				com_events += LOTS_OF_EVENTS;
 				com->state ^= (CS_ODONE | CS_BUSY);
-				schedsoftcom();	/* handle at high level ASAP */
+				setsofttty();	/* handle at high level ASAP */
 			}
 		}
 
 		/* finished? */
+#ifndef COM_MULTIPORT
 		if ((inb(com->int_id_port) & IIR_IMASK) == IIR_NOPEND)
-#ifdef COM_MULTIPORT
-			return (donesomething);
-#else
-			return;
 #endif /* COM_MULTIPORT */
+			return;
 	}
 }
 
@@ -1063,21 +1039,19 @@ sioioctl(dev, cmd, data, flag, p)
 
 	com = com_addr(UNIT(dev));
 	tp = com->tp;
-
 	error = (*linesw[tp->t_line].l_ioctl)(tp, cmd, data, flag);
 	if (error >= 0)
 		return (error);
 	error = ttioctl(tp, cmd, data, flag);
-#ifdef COM_BIDIR
-	/* XXX: plug security hole while stucky bits not yet implemented */
 
+#ifdef COM_BIDIR
+	/* XXX: plug security hole while sticky bits not yet implemented */
 	if (com->bidir && com->active_in && p->p_ucred->cr_uid != 0)
 		tp->t_cflag &= ~CLOCAL;
 #endif
-	if (error >= 0) {
-		tp->t_lowat = 0;	/* XXX part of ttywait() deadlock fix */
+
+	if (error >= 0)
 		return (error);
-	}
 
 	iobase = com->iobase;
 	s = spltty();
@@ -1204,11 +1178,10 @@ comflush(com)
 	com->tp->t_state &= ~TS_BUSY;
 }
 
-static void
-compoll()
+void
+siopoll()
 {
 	static bool_t	awake = FALSE;
-	struct com_s	*com;
 	int		s;
 	int		unit;
 
@@ -1225,6 +1198,7 @@ compoll()
 repeat:
 	for (unit = 0; unit < NSIO; ++unit) {
 		u_char          *buf;
+		struct com_s    *com;
 		u_char		*ibuf;
 		int		incc;
 		struct tty	*tp;
@@ -1234,11 +1208,11 @@ repeat:
 			continue;
 		tp = com->tp;
 
-		buf = NULL;     /* avoid compiler warning */
 		/* switch the role of the low-level input buffers */
-		if (com->iptr == (ibuf = com->ibuf))
+		if (com->iptr == (ibuf = com->ibuf)) {
+			buf = NULL;     /* not used, but compiler can't tell */
 			incc = 0;
-		else {
+		} else {
 			buf = ibuf;
 			disable_intr();
 			incc = com->iptr - buf;
@@ -1280,8 +1254,7 @@ repeat:
 #ifdef COM_BIDIR
 					wakeup((caddr_t) &com->active_in);
 #endif /* COM_BIDIR */
-				}
-				else
+				} else
 					(*linesw[tp->t_line].l_modem)(tp, 0);
 			}
 		}
@@ -1289,18 +1262,14 @@ repeat:
 		/* XXX */
 		if (TRUE) {
 			u_int delta;
-			u_int delta_error_counts[CE_NTYPES];
 			int errnum;
 			u_long total;
 
+			for (errnum = 0; errnum < CE_NTYPES; ++errnum) {
 			disable_intr();
-			bcopy(com->delta_error_counts, delta_error_counts,
-			      sizeof delta_error_counts);
-			bzero(com->delta_error_counts,
-			      sizeof delta_error_counts);
+				delta = com->delta_error_counts[errnum];
+				com->delta_error_counts[errnum] = 0;
 			enable_intr();
-			for (errnum = 0; errnum < CE_NTYPES; ++errnum) {
-				delta = delta_error_counts[errnum];
 				if (delta != 0) {
 					total =
 					com->error_counts[errnum] += delta;
@@ -1359,8 +1328,7 @@ repeat:
 				tp->t_lflag &= ~FLUSHO;
 				ttstart(tp);
 			}
-		}
-		else {
+		} else {
 			do {
 				u_char	line_status;
 				int	recv_data;
@@ -1474,9 +1442,9 @@ retry:
 
 	/*
 	 * XXX - clearing CS_TTGO is not sufficient to stop further output,
-	 * because compoll() calls comstart() which set it again because
-	 * TS_TTSTOP is set.  Clearing TS_TTSTOP would not be sufficient,
-	 * for similar reasons.
+	 * because siopoll() calls comstart() which usually sets it again
+	 * because TS_TTSTOP is clear.  Setting TS_TTSTOP would not be
+	 * sufficient, for similar reasons.
 	 */
 	if ((inb(com->line_status_port) & (LSR_TSRE | LSR_TXRDY))
 	       != (LSR_TSRE | LSR_TXRDY))
@@ -1508,7 +1476,17 @@ retry:
 			com->state &= ~CS_ODEVREADY;
 	}
 
-	siointr(unit);		/* recover from fiddling with CS_TTGO */
+	/*
+	 * Recover from fiddling with CS_TTGO.  We used to call siointr()
+	 * unconditionally, but that defeated the careful discarding of
+	 * stale input in sioopen().
+	 *
+	 * XXX sioopen() is not careful waiting for carrier for the callout
+	 * case.
+	 */
+	if (com->state >= (CS_BUSY | CS_TTGO))
+		siointr(unit);
+
 	enable_intr();
 	splx(s);
 	return (0);
@@ -1533,8 +1511,7 @@ comstart(tp)
 	if (tp->t_state & TS_RTS_IFLOW) {
 		if (com->mcr_image & MCR_RTS && com->state & CS_RTS_IFLOW)
 			outb(com->modem_ctl_port, com->mcr_image &= ~MCR_RTS);
-	}
-	else {
+	} else {
 		if (!(com->mcr_image & MCR_RTS) && com->iptr < com->ihighwater)
 			outb(com->modem_ctl_port, com->mcr_image |= MCR_RTS);
 	}
@@ -1556,8 +1533,7 @@ comstart(tp)
 		disable_intr();
 		siointr(unit);
 		enable_intr();
-	}
-	else if (RB_LEN(&tp->t_out) != 0) {
+	} else if (RB_LEN(&tp->t_out) != 0) {
 		tp->t_state |= TS_BUSY;
 		com->ocount = RB_CONTIGGET(&tp->t_out);
 		disable_intr();
@@ -1593,6 +1569,15 @@ siostop(tp, rw)
 	enable_intr();
 }
 
+int
+sioselect(dev, rw, p)
+	dev_t		dev;
+	int		rw;
+	struct proc	*p;
+{
+	return ttselect(dev & ~COM_CALLOUTMASK, rw, p);
+}
+
 static void
 commctl(com, bits, how)
 	struct com_s	*com;
@@ -1620,16 +1605,17 @@ comwakeup(chan, ticks)
 	caddr_t chan;
 	int ticks;
 {
-	struct com_s	*com;
 	int		unit;
 
 	timeout(comwakeup, (caddr_t) NULL, hz / 100);
 	if (com_events != 0)
-		/* schedule compoll() to run when the cpl allows */
-		schedsoftcom();
+		/* schedule siopoll() to run when the cpl allows */
+		setsofttty();
 
 	/* recover from lost output interrupts */
 	for (unit = 0; unit < NSIO; ++unit) {
+		struct com_s	*com;
+
 		com = com_addr(unit);
 		if (com != NULL && com->state >= (CS_BUSY | CS_TTGO)) {
 			disable_intr();
@@ -1643,7 +1629,7 @@ comwakeup(chan, ticks)
 void
 softsio1()
 {
-	compoll();
+	siopoll();
 }
 
 /*
@@ -1674,7 +1660,6 @@ siocnprobe(cp)
 
 	/* initialize required fields */
 	cp->cn_dev = makedev(commajor, unit);
-	cp->cn_tp = &sio_tty[unit];
 #ifdef	COMCONSOLE
 	cp->cn_pri = CN_REMOTE;		/* Force a serial port console */
 #else
@@ -1775,49 +1760,4 @@ siocnputc(dev, c)
 	splx(s);
 }
 
-/*
- * XXX - sioselect() is almost a copy of ttselect().  It is required because
- * ttselect() can't determine the tty struct because stuff is encoded in the
- * high bit of the minor number.
- */
-int
-sioselect(dev, rw, p)
-	dev_t dev;
-	int rw;
-	struct proc *p;
-{
-	struct tty *tp = &sio_tty[UNIT(dev)];
-	int nread;
-	int s = spltty();
-        struct proc *selp;
-
-	switch (rw) {
-
-	case FREAD:
-		nread = ttnread(tp);
-		if (nread > 0 ||
-		   ((tp->t_cflag&CLOCAL) == 0 && (tp->t_state&TS_CARR_ON) == 0))
-			goto win;
-		if (tp->t_rsel && (selp = pfind(tp->t_rsel)) && selp->p_wchan == (caddr_t)&selwait)
-			tp->t_state |= TS_RCOLL;
-		else
-			tp->t_rsel = p->p_pid;
-		break;
-
-	case FWRITE:
-		if (RB_LEN(&tp->t_out) <= tp->t_lowat)
-			goto win;
-		if (tp->t_wsel && (selp = pfind(tp->t_wsel)) && selp->p_wchan == (caddr_t)&selwait)
-			tp->t_state |= TS_WCOLL;
-		else
-			tp->t_wsel = p->p_pid;
-		break;
-	}
-	splx(s);
-	return (0);
-  win:
-	splx(s);
-	return (1);
-}
-
 #endif /* NSIO > 0 */
diff --git a/sys/isa/sio.c b/sys/isa/sio.c
index 21c9f90..30c9768 100644
--- a/sys/isa/sio.c
+++ b/sys/isa/sio.c
@@ -31,7 +31,7 @@
  * SUCH DAMAGE.
  *
  *	from: @(#)com.c	7.5 (Berkeley) 5/16/91
- *	$Id: sio.c,v 1.22 1994/01/11 18:31:45 ache Exp $
+ *	$Id: sio.c,v 1.23 1994/01/31 06:12:18 davidg Exp $
  */
 
 #include "sio.h"
@@ -71,7 +71,7 @@
 #define	UNIT(x)		(minor(x))	/* XXX */
 #else /* COM_BIDIR */
 #define COM_UNITMASK    0x7f
-#define COM_CALLOUTMASK 0x80
+#define COM_CALLOUTMASK 0x80		/* for both minor and dev */
 #define UNIT(x)         (minor(x) & COM_UNITMASK)
 #define CALLOUT(x)      (minor(x) & COM_CALLOUTMASK)
 #endif /* COM_BIDIR */
@@ -98,7 +98,7 @@
 #endif
 
 #define	com_scr		7	/* scratch register for 16450-16550 (R/W) */
-#define	schedsoftcom()	(ipending |= 1 << (16 + 4))	/* XXX */
+#define setsofttty()    (ipending |= 1 << 4)     /* XXX */
 
 /*
  * Input buffer watermarks.
@@ -148,7 +148,6 @@ static	char	*error_desc[] = {
 
 /* types.  XXX - should be elsewhere */
 typedef u_int	Port_t;		/* hardware port */
-typedef int	Bool_t;		/* promoted boolean */
 typedef u_char	bool_t;		/* boolean */
 
 /* com device structure */
@@ -167,6 +166,7 @@ struct com_s {
 	bool_t	multiport;	/* is this unit part of a multiport device? */
 #endif /* COM_MULTIPORT */
 	int	dtr_wait;	/* time to hold DTR down on close (* 1/HZ) */
+	u_int	tx_fifo_size;
 
 	/*
 	 * The high level of the driver never reads status registers directly
@@ -228,6 +228,7 @@ void	siocnprobe	__P((struct consdev *cp));
 void	siocnputc	__P((Dev_t dev, int c));
 int	sioopen		__P((Dev_t dev, int oflags, int devtype,
 			     struct proc *p));
+void	siopoll		__P((void));
 int	sioread		__P((Dev_t dev, struct uio *uio, int ioflag));
 int	sioselect	__P((Dev_t dev, int rw, struct proc *p));
 void	siostop		__P((struct tty *tp, int rw));
@@ -239,12 +240,11 @@ static	void	comflush	__P((struct com_s *com));
 static	void	comhardclose	__P((struct com_s *com));
 static	void	cominit		__P((int unit, int rate));
 #ifdef COM_MULTIPORT
-static  bool_t  comintr1        __P((struct com_s *com));
+static	void	comintr1	__P((struct com_s *com));
 #endif /* COM_MULTIPORT */
 static	void	commctl		__P((struct com_s *com, int bits, int how));
 static	int	comparam	__P((struct tty *tp, struct termios *t));
 static	int	sioprobe	__P((struct isa_device *dev));
-static	void	compoll		__P((void));
 static  void    comstart        __P((struct tty *tp));
 static  void    comwakeup       __P((caddr_t chan, int ticks));
 static	int	tiocm_xxx2mcr	__P((int tiocm_xxx));
@@ -386,12 +386,14 @@ sioprobe(dev)
 	    || isa_irq_pending(dev)
 	    || (inb(iobase + com_iir) & IIR_IMASK) != IIR_NOPEND)
 		result = 0;
+	if (result == 0)
+		outb(iobase + com_mcr, 0);
 
 	enable_intr();
 	return (result);
 }
 
-static int			/* XXX - should be void */
+static int
 sioattach(isdp)
 	struct isa_device	*isdp;
 {
@@ -423,6 +425,7 @@ sioattach(isdp)
 	com->cfcr_image = CFCR_8BITS;
 	com->mcr_image = MCR_IENABLE;
 	com->dtr_wait = 200;
+	com->tx_fifo_size = 1;
 	com->iptr = com->ibuf = com->ibuf1;
 	com->ibufend = com->ibuf1 + RS_IBUFSIZE;
 	com->ihighwater = com->ibuf1 + RS_IHIGHWATER;
@@ -433,14 +436,6 @@ sioattach(isdp)
 	com->line_status_port = iobase + com_lsr;
 	com->modem_status_port = iobase + com_msr;
 	com->tp = &sio_tty[unit];
-#ifdef COM_BIDIR
-	/*
-	 * if bidirectional ports possible, clear the bidir port info;
-	 */
-	com->bidir = FALSE;
-	com->active = FALSE;
-	com->active_in = com->active_out = FALSE;
-#endif /* COM_BIDIR */
 
 	/* attempt to determine UART type */
 	printf("sio%d: type", unit);
@@ -481,6 +476,7 @@ sioattach(isdp)
 			printf(" fifo software disabled");
 		} else {
 			com->hasfifo = TRUE;
+			com->tx_fifo_size = 16;
 		}
 		break;
 	}
@@ -503,8 +499,7 @@ determined_type: ;
 		masterdev = find_isadev(isa_devtab_tty, &siodriver,
 					COM_MPMASTER(isdp));
 		outb(masterdev->id_iobase + com_scr, 0x80);
-	}
-	else
+	} else
 		com->multiport = FALSE;
 #endif /* COM_MULTIPORT */
 	printf("\n");
@@ -522,8 +517,7 @@ determined_type: ;
 				 */
 				printf("sio%d: ", unit);
 				kgdb_connect(1);
-			}
-			else
+			} else
 				printf("sio%d: kgdb enabled\n", unit);
 		}
 	}
@@ -667,10 +661,10 @@ bidir_open_top:
 			 * can be turned off.
 			 */
 			tp->t_iflag = 0;
+			tp->t_oflag = 0;
 #ifdef COMCONSOLE
+			if (unit == comconsole)
 			tp->t_oflag = TTYDEF_OFLAG;
-#else
-			tp->t_oflag = 0;
 #endif
 			tp->t_cflag = CREAD | CS8 | HUPCL;
 			tp->t_lflag = 0;
@@ -695,22 +689,6 @@ bidir_open_top:
 		if (error != 0)
 			goto out;
 		ttsetwater(tp);
-
-		/*
-		 * XXX temporary fix for deadlock in ttywait().
-		 *
-		 * If two processes wait for output to drain from the same
-		 * tty, and the amount of output to drain is > 0 and
-		 * <= tp->t_lowat, then the processes will take turns
-		 * uselessly waking each other up until the output drains,
-		 * with cpl higher than spltty() throughout.
-		 *
-		 * The sleep address and TS_ASLEEP flag ought to be different
-		 * for the different events (output done) and (output almost
-		 * done).
-		 */
-		tp->t_lowat = 0;
-
 		iobase = com->iobase;
 		if (com->hasfifo) {
 			/* (re)enable and drain FIFO */
@@ -728,8 +706,7 @@ bidir_open_top:
 		enable_intr();
 		if (com->prev_modem_status & MSR_DCD || FAKE_DCD(unit))
 			tp->t_state |= TS_CARR_ON;
-	}
-	else if (tp->t_state & TS_XCLUDE && p->p_ucred->cr_uid != 0) {
+	} else if (tp->t_state & TS_XCLUDE && p->p_ucred->cr_uid != 0) {
 		splx(s);
 		return (EBUSY);
 	}
@@ -799,18 +776,21 @@ comhardclose(com)
 	Port_t		iobase;
 	int		s;
 	struct tty	*tp;
+	int		unit;
 
 	s = spltty();
 	iobase = com->iobase;
 	outb(iobase + com_cfcr, com->cfcr_image &= ~CFCR_SBREAK);
+	unit = com - &com_structs[0];
 #ifdef KGDB
 	/* do not disable interrupts or hang up if debugging */
-	if (kgdb_dev != makedev(commajor, com - &com_structs[0]))
+	if (kgdb_dev != makedev(commajor, unit))
 #endif
 	{
 		outb(iobase + com_ier, 0);
 		tp = com->tp;
 		if (tp->t_cflag & HUPCL || tp->t_state & TS_WOPEN
+		    || !(com->prev_modem_status & MSR_DCD) && !FAKE_DCD(unit)
 		    || !(tp->t_state & TS_ISOPEN)) {
 			commctl(com, MCR_RTS, DMSET);
 			if (com->dtr_wait != 0)
@@ -887,30 +867,28 @@ siointr(unit)
 	 * If the IRQ signal is just an OR of the IRQ signals from several
 	 * devices, then the edge from one may be lost because another is
 	 * on.
-	 *
-	 * XXX getting the status from comintr1() is not best and may be
-	 * incorrect.  It would be better to test the int_id's in a tight
-	 * loop.  If each is off when it is tested, then they all must
-	 * have been off at the start.
 	 */
 	do {
 		possibly_more_intrs = FALSE;
 		for (unit = 0; unit < NSIO; ++unit) {
 			com = com_addr(unit);
-			if (com != NULL) {
+			if (com != NULL
+			    && (inb(com->int_id_port) & IIR_IMASK)
+			       != IIR_NOPEND) {
 				/*
 				 * XXX call comintr1() instead of here from
 				 * comwakeup().  The interrupt edge problem
 				 * only exists for real interrupts.
 				 */
-				possibly_more_intrs |= comintr1(com);
+				comintr1(com);
+				possibly_more_intrs = TRUE;
 			}
 		}
 	} while (possibly_more_intrs);
 	return;
 }
 
-static bool_t
+static void
 comintr1(com)
 	struct com_s *com;
 {
@@ -918,9 +896,6 @@ comintr1(com)
 	u_char		modem_status;
 	u_char		*ioptr;
 	u_char		recv_data;
-	bool_t		donesomething;
-
-	donesomething = FALSE;
 #endif /* COM_MULTIPORT */
 
 	while (TRUE) {
@@ -929,9 +904,6 @@ comintr1(com)
 		/* input event? (check first to help avoid overruns) */
 		while (line_status & LSR_RCV_MASK) {
 			/* break/unnattached error bits or real input? */
-#ifdef COM_MULTIPORT
-			donesomething = TRUE;
-#endif /* COM_MULTIPORT */
 			if (!(line_status & LSR_RXRDY))
 				recv_data = 0;
 			else
@@ -951,9 +923,9 @@ comintr1(com)
 				CE_RECORD(com, CE_INTERRUPT_BUF_OVERFLOW);
 			else {
 				++com_events;
-#if 0
+#if 0 /* for testing input latency vs efficiency */
 if (com->iptr - com->ibuf == 8)
-	schedsoftcom();
+	setsofttty();
 #endif
 				ioptr[0] = recv_data;
 				ioptr[CE_INPUT_OFFSET] = line_status;
@@ -983,14 +955,11 @@ if (com->iptr - com->ibuf == 8)
 			 * UARTs mess them up, and it's easy to remember the
 			 * previous bits and calculate the delta.
 			 */
-#ifdef COM_MULTIPORT
-			donesomething = TRUE;
-#endif /* COM_MULTIPORT */
 			com->last_modem_status = modem_status;
 			if (!(com->state & CS_CHECKMSR)) {
 				com_events += LOTS_OF_EVENTS;
 				com->state |= CS_CHECKMSR;
-				schedsoftcom();
+				setsofttty();
 			}
 
 			/* handle CTS change immediately for crisp flow ctl */
@@ -1005,28 +974,35 @@ if (com->iptr - com->ibuf == 8)
 		/* output queued and everything ready? */
 		if (line_status & LSR_TXRDY
 		    && com->state >= (CS_ODEVREADY | CS_BUSY | CS_TTGO)) {
-#ifdef COM_MULTIPORT
-			donesomething = TRUE;
-#endif /* COM_MULTIPORT */
 			ioptr = com->optr;
-			outb(com->data_port, *ioptr);
+			if (com->tx_fifo_size > 1) {
+				u_int	ocount;
+
+				ocount = com->obufend - ioptr;
+				if (ocount > com->tx_fifo_size)
+					ocount = com->tx_fifo_size;
+				com->bytes_out += ocount;
+				do
+					outb(com->data_port, *ioptr++);
+				while (--ocount != 0);
+			} else {
+				outb(com->data_port, *ioptr++);
 			++com->bytes_out;
-			com->optr = ++ioptr;
+			}
+			com->optr = ioptr;
 			if (ioptr >= com->obufend) {
 				/* output just completed */
 				com_events += LOTS_OF_EVENTS;
 				com->state ^= (CS_ODONE | CS_BUSY);
-				schedsoftcom();	/* handle at high level ASAP */
+				setsofttty();	/* handle at high level ASAP */
 			}
 		}
 
 		/* finished? */
+#ifndef COM_MULTIPORT
 		if ((inb(com->int_id_port) & IIR_IMASK) == IIR_NOPEND)
-#ifdef COM_MULTIPORT
-			return (donesomething);
-#else
-			return;
 #endif /* COM_MULTIPORT */
+			return;
 	}
 }
 
@@ -1063,21 +1039,19 @@ sioioctl(dev, cmd, data, flag, p)
 
 	com = com_addr(UNIT(dev));
 	tp = com->tp;
-
 	error = (*linesw[tp->t_line].l_ioctl)(tp, cmd, data, flag);
 	if (error >= 0)
 		return (error);
 	error = ttioctl(tp, cmd, data, flag);
-#ifdef COM_BIDIR
-	/* XXX: plug security hole while stucky bits not yet implemented */
 
+#ifdef COM_BIDIR
+	/* XXX: plug security hole while sticky bits not yet implemented */
 	if (com->bidir && com->active_in && p->p_ucred->cr_uid != 0)
 		tp->t_cflag &= ~CLOCAL;
 #endif
-	if (error >= 0) {
-		tp->t_lowat = 0;	/* XXX part of ttywait() deadlock fix */
+
+	if (error >= 0)
 		return (error);
-	}
 
 	iobase = com->iobase;
 	s = spltty();
@@ -1204,11 +1178,10 @@ comflush(com)
 	com->tp->t_state &= ~TS_BUSY;
 }
 
-static void
-compoll()
+void
+siopoll()
 {
 	static bool_t	awake = FALSE;
-	struct com_s	*com;
 	int		s;
 	int		unit;
 
@@ -1225,6 +1198,7 @@ compoll()
 repeat:
 	for (unit = 0; unit < NSIO; ++unit) {
 		u_char          *buf;
+		struct com_s    *com;
 		u_char		*ibuf;
 		int		incc;
 		struct tty	*tp;
@@ -1234,11 +1208,11 @@ repeat:
 			continue;
 		tp = com->tp;
 
-		buf = NULL;     /* avoid compiler warning */
 		/* switch the role of the low-level input buffers */
-		if (com->iptr == (ibuf = com->ibuf))
+		if (com->iptr == (ibuf = com->ibuf)) {
+			buf = NULL;     /* not used, but compiler can't tell */
 			incc = 0;
-		else {
+		} else {
 			buf = ibuf;
 			disable_intr();
 			incc = com->iptr - buf;
@@ -1280,8 +1254,7 @@ repeat:
 #ifdef COM_BIDIR
 					wakeup((caddr_t) &com->active_in);
 #endif /* COM_BIDIR */
-				}
-				else
+				} else
 					(*linesw[tp->t_line].l_modem)(tp, 0);
 			}
 		}
@@ -1289,18 +1262,14 @@ repeat:
 		/* XXX */
 		if (TRUE) {
 			u_int delta;
-			u_int delta_error_counts[CE_NTYPES];
 			int errnum;
 			u_long total;
 
+			for (errnum = 0; errnum < CE_NTYPES; ++errnum) {
 			disable_intr();
-			bcopy(com->delta_error_counts, delta_error_counts,
-			      sizeof delta_error_counts);
-			bzero(com->delta_error_counts,
-			      sizeof delta_error_counts);
+				delta = com->delta_error_counts[errnum];
+				com->delta_error_counts[errnum] = 0;
 			enable_intr();
-			for (errnum = 0; errnum < CE_NTYPES; ++errnum) {
-				delta = delta_error_counts[errnum];
 				if (delta != 0) {
 					total =
 					com->error_counts[errnum] += delta;
@@ -1359,8 +1328,7 @@ repeat:
 				tp->t_lflag &= ~FLUSHO;
 				ttstart(tp);
 			}
-		}
-		else {
+		} else {
 			do {
 				u_char	line_status;
 				int	recv_data;
@@ -1474,9 +1442,9 @@ retry:
 
 	/*
 	 * XXX - clearing CS_TTGO is not sufficient to stop further output,
-	 * because compoll() calls comstart() which set it again because
-	 * TS_TTSTOP is set.  Clearing TS_TTSTOP would not be sufficient,
-	 * for similar reasons.
+	 * because siopoll() calls comstart() which usually sets it again
+	 * because TS_TTSTOP is clear.  Setting TS_TTSTOP would not be
+	 * sufficient, for similar reasons.
 	 */
 	if ((inb(com->line_status_port) & (LSR_TSRE | LSR_TXRDY))
 	       != (LSR_TSRE | LSR_TXRDY))
@@ -1508,7 +1476,17 @@ retry:
 			com->state &= ~CS_ODEVREADY;
 	}
 
-	siointr(unit);		/* recover from fiddling with CS_TTGO */
+	/*
+	 * Recover from fiddling with CS_TTGO.  We used to call siointr()
+	 * unconditionally, but that defeated the careful discarding of
+	 * stale input in sioopen().
+	 *
+	 * XXX sioopen() is not careful waiting for carrier for the callout
+	 * case.
+	 */
+	if (com->state >= (CS_BUSY | CS_TTGO))
+		siointr(unit);
+
 	enable_intr();
 	splx(s);
 	return (0);
@@ -1533,8 +1511,7 @@ comstart(tp)
 	if (tp->t_state & TS_RTS_IFLOW) {
 		if (com->mcr_image & MCR_RTS && com->state & CS_RTS_IFLOW)
 			outb(com->modem_ctl_port, com->mcr_image &= ~MCR_RTS);
-	}
-	else {
+	} else {
 		if (!(com->mcr_image & MCR_RTS) && com->iptr < com->ihighwater)
 			outb(com->modem_ctl_port, com->mcr_image |= MCR_RTS);
 	}
@@ -1556,8 +1533,7 @@ comstart(tp)
 		disable_intr();
 		siointr(unit);
 		enable_intr();
-	}
-	else if (RB_LEN(&tp->t_out) != 0) {
+	} else if (RB_LEN(&tp->t_out) != 0) {
 		tp->t_state |= TS_BUSY;
 		com->ocount = RB_CONTIGGET(&tp->t_out);
 		disable_intr();
@@ -1593,6 +1569,15 @@ siostop(tp, rw)
 	enable_intr();
 }
 
+int
+sioselect(dev, rw, p)
+	dev_t		dev;
+	int		rw;
+	struct proc	*p;
+{
+	return ttselect(dev & ~COM_CALLOUTMASK, rw, p);
+}
+
 static void
 commctl(com, bits, how)
 	struct com_s	*com;
@@ -1620,16 +1605,17 @@ comwakeup(chan, ticks)
 	caddr_t chan;
 	int ticks;
 {
-	struct com_s	*com;
 	int		unit;
 
 	timeout(comwakeup, (caddr_t) NULL, hz / 100);
 	if (com_events != 0)
-		/* schedule compoll() to run when the cpl allows */
-		schedsoftcom();
+		/* schedule siopoll() to run when the cpl allows */
+		setsofttty();
 
 	/* recover from lost output interrupts */
 	for (unit = 0; unit < NSIO; ++unit) {
+		struct com_s	*com;
+
 		com = com_addr(unit);
 		if (com != NULL && com->state >= (CS_BUSY | CS_TTGO)) {
 			disable_intr();
@@ -1643,7 +1629,7 @@ comwakeup(chan, ticks)
 void
 softsio1()
 {
-	compoll();
+	siopoll();
 }
 
 /*
@@ -1674,7 +1660,6 @@ siocnprobe(cp)
 
 	/* initialize required fields */
 	cp->cn_dev = makedev(commajor, unit);
-	cp->cn_tp = &sio_tty[unit];
 #ifdef	COMCONSOLE
 	cp->cn_pri = CN_REMOTE;		/* Force a serial port console */
 #else
@@ -1775,49 +1760,4 @@ siocnputc(dev, c)
 	splx(s);
 }
 
-/*
- * XXX - sioselect() is almost a copy of ttselect().  It is required because
- * ttselect() can't determine the tty struct because stuff is encoded in the
- * high bit of the minor number.
- */
-int
-sioselect(dev, rw, p)
-	dev_t dev;
-	int rw;
-	struct proc *p;
-{
-	struct tty *tp = &sio_tty[UNIT(dev)];
-	int nread;
-	int s = spltty();
-        struct proc *selp;
-
-	switch (rw) {
-
-	case FREAD:
-		nread = ttnread(tp);
-		if (nread > 0 ||
-		   ((tp->t_cflag&CLOCAL) == 0 && (tp->t_state&TS_CARR_ON) == 0))
-			goto win;
-		if (tp->t_rsel && (selp = pfind(tp->t_rsel)) && selp->p_wchan == (caddr_t)&selwait)
-			tp->t_state |= TS_RCOLL;
-		else
-			tp->t_rsel = p->p_pid;
-		break;
-
-	case FWRITE:
-		if (RB_LEN(&tp->t_out) <= tp->t_lowat)
-			goto win;
-		if (tp->t_wsel && (selp = pfind(tp->t_wsel)) && selp->p_wchan == (caddr_t)&selwait)
-			tp->t_state |= TS_WCOLL;
-		else
-			tp->t_wsel = p->p_pid;
-		break;
-	}
-	splx(s);
-	return (0);
-  win:
-	splx(s);
-	return (1);
-}
-
 #endif /* NSIO > 0 */