/*	$OpenBSD: z8530tty.c,v 1.26 2015/02/05 12:04:58 miod Exp $	*/
/*	$NetBSD: z8530tty.c,v 1.77 2001/05/30 15:24:24 lukem Exp $	*/

/*-
 * Copyright (c) 1993, 1994, 1995, 1996, 1997, 1998, 1999
 *	Charles M. Hannum.  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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by Charles M. Hannum.
 * 4. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 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) 1994 Gordon W. Ross
 * Copyright (c) 1992, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This software was developed by the Computer Systems Engineering group
 * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
 * contributed to Berkeley.
 *
 * All advertising materials mentioning features or use of this software
 * must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Lawrence Berkeley Laboratory.
 *
 * 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.
 *
 *	@(#)zs.c	8.1 (Berkeley) 7/19/93
 */

/*
 * Zilog Z8530 Dual UART driver (tty interface)
 *
 * This is the "slave" driver that will be attached to
 * the "zsc" driver for plain "tty" async. serial lines.
 *
 * Credits, history:
 *
 * The original version of this code was the sparc/dev/zs.c driver
 * as distributed with the Berkeley 4.4 Lite release.  Since then,
 * Gordon Ross reorganized the code into the current parent/child
 * driver scheme, separating the Sun keyboard and mouse support
 * into independent child drivers.
 *
 * RTS/CTS flow-control support was a collaboration of:
 *	Gordon Ross <gwr@NetBSD.org>,
 *	Bill Studenmund <wrstuden@loki.stanford.edu>
 *	Ian Dall <Ian.Dall@dsto.defence.gov.au>
 *
 * The driver was massively overhauled in November 1997 by Charles Hannum,
 * fixing *many* bugs, and substantially improving performance.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/proc.h>
#include <sys/device.h>
#include <sys/conf.h>
#include <sys/file.h>
#include <sys/ioctl.h>
#include <sys/malloc.h>
#include <sys/tty.h>
#include <sys/time.h>
#include <sys/kernel.h>
#include <sys/syslog.h>

#include <dev/ic/z8530reg.h>
#include <machine/z8530var.h>

#include <dev/cons.h>

/*
 * Allow the MD var.h to override the default CFLAG so that
 * console messages during boot come out with correct parity.
 */
#ifndef	ZSTTY_DEF_CFLAG
#define	ZSTTY_DEF_CFLAG	TTYDEF_CFLAG
#endif

/*
 * How many input characters we can buffer.
 * The port-specific var.h may override this.
 * Note: must be a power of two!
 */
#ifndef	ZSTTY_RING_SIZE
#define	ZSTTY_RING_SIZE	2048
#endif

struct cfdriver zstty_cd = {
	NULL, "zstty", DV_TTY
};

/*
 * Make this an option variable one can patch.
 * But be warned:  this must be a power of 2!
 */
u_int zstty_rbuf_size = ZSTTY_RING_SIZE;

/* Stop input when 3/4 of the ring is full; restart when only 1/4 is full. */
u_int zstty_rbuf_hiwat = (ZSTTY_RING_SIZE * 1) / 4;
u_int zstty_rbuf_lowat = (ZSTTY_RING_SIZE * 3) / 4;

struct zstty_softc {
	struct	device zst_dev;		/* required first: base device */
	struct  tty *zst_tty;
	struct	zs_chanstate *zst_cs;

	struct timeout zst_diag_ch;

	u_int zst_overflows,
	      zst_floods,
	      zst_errors;

	int zst_hwflags,	/* see z8530var.h */
	    zst_swflags;	/* TIOCFLAG_SOFTCAR, ... <ttycom.h> */

	u_int zst_r_hiwat,
	      zst_r_lowat;
	uint8_t *volatile zst_rbget,
		*volatile zst_rbput;
	volatile u_int zst_rbavail;
	uint8_t *zst_rbuf,
		*zst_ebuf;

	/*
	 * The transmit byte count and address are used for pseudo-DMA
	 * output in the hardware interrupt code.  PDMA can be suspended
	 * to get pending changes done; heldtbc is used for this.  It can
	 * also be stopped for ^S; this sets TS_TTSTOP in tp->t_state.
	 */
	uint8_t *zst_tba;		/* transmit buffer address */
	u_int zst_tbc,			/* transmit byte count */
	      zst_heldtbc;		/* held tbc while xmission stopped */

	/* Flags to communicate with zstty_softint() */
	volatile uint8_t zst_rx_flags,	/* receiver blocked */
#define	RX_TTY_BLOCKED		0x01
#define	RX_TTY_OVERFLOWED	0x02
#define	RX_IBUF_BLOCKED		0x04
#define	RX_IBUF_OVERFLOWED	0x08
#define	RX_ANY_BLOCK		0x0f
			zst_tx_busy,	/* working on an output chunk */
			zst_tx_done,	/* done with one output chunk */
			zst_tx_stopped,	/* H/W level stop (lost CTS) */
			zst_st_check,	/* got a status interrupt */
			zst_rx_ready;

	/* PPS signal on DCD, with or without inkernel clock disciplining */
	uint8_t  zst_ppsmask;			/* pps signal mask */
	uint8_t  zst_ppsassert;			/* pps leading edge */
	uint8_t  zst_ppsclear;			/* pps trailing edge */
};

/* Definition of the driver for autoconfig. */
int	zstty_match(struct device *, void *, void *);
void	zstty_attach(struct device *, struct device *, void *);

const struct cfattach zstty_ca = {
	sizeof(struct zstty_softc), zstty_match, zstty_attach
};

cdev_decl(zs);

struct zsops zsops_tty;

void zs_shutdown(struct zstty_softc *);
void	zsstart(struct tty *);
int	zsparam(struct tty *, struct termios *);
void zs_modem(struct zstty_softc *, int);
void tiocm_to_zs(struct zstty_softc *, u_long, int);
int  zs_to_tiocm(struct zstty_softc *);
int    zshwiflow(struct tty *, int);
void  zs_hwiflow(struct zstty_softc *);
void zs_maskintr(struct zstty_softc *);

struct zstty_softc *zs_device_lookup(struct cfdriver *, int);

/* Low-level routines. */
void zstty_rxint(struct zs_chanstate *);
void zstty_stint(struct zs_chanstate *, int);
void zstty_txint(struct zs_chanstate *);
void zstty_softint(struct zs_chanstate *);
void zstty_diag(void *);

#define	ZSUNIT(x)	(minor(x) & 0x7f)
#define	ZSDIALOUT(x)	(minor(x) & 0x80)

struct zstty_softc *
zs_device_lookup(struct cfdriver *cf, int unit)
{
	return (struct zstty_softc *)device_lookup(cf, unit);
}

/*
 * zstty_match: how is this zs channel configured?
 */
int
zstty_match(struct device *parent, void *vcf, void *aux)
{
	struct cfdata *cf = vcf;
	struct zsc_attach_args *args = aux;

	/* Exact match is better than wildcard. */
	if (cf->cf_loc[0] == args->channel)
		return 2;

	/* This driver accepts wildcard. */
	if (cf->cf_loc[0] == -1)
		return 1;

	return 0;
}

void
zstty_attach(struct device *parent, struct device *self, void *aux)
{
	struct zsc_softc *zsc = (struct zsc_softc *)parent;
	struct zstty_softc *zst = (struct zstty_softc *)self;
	struct cfdata *cf = self->dv_cfdata;
	struct zsc_attach_args *args = aux;
	struct zs_chanstate *cs;
	struct tty *tp;
	int channel, s, tty_unit;
	dev_t dev;
	const char *i, *o;
	int dtr_on;
	int resetbit;

	timeout_set(&zst->zst_diag_ch, zstty_diag, zst);

	tty_unit = zst->zst_dev.dv_unit;
	channel = args->channel;
	cs = zsc->zsc_cs[channel];
	cs->cs_private = zst;
	cs->cs_ops = &zsops_tty;

	zst->zst_cs = cs;
	zst->zst_swflags = cf->cf_flags;	/* softcar, etc. */
	zst->zst_hwflags = args->hwflags;
	dev = makedev(zs_major, tty_unit);

	if (zst->zst_swflags)
		printf(" flags 0x%x", zst->zst_swflags);

	if (ISSET(zst->zst_hwflags, ZS_HWFLAG_NO_DCD))
		SET(zst->zst_swflags, TIOCFLAG_SOFTCAR);

	/*
	 * Check whether we serve as a console device.
	 * XXX - split console input/output channels aren't
	 *	 supported yet on /dev/console
	 */
	i = o = NULL;
	if ((zst->zst_hwflags & ZS_HWFLAG_CONSOLE_INPUT) != 0) {
		i = " input";
		if ((args->hwflags & ZS_HWFLAG_USE_CONSDEV) != 0) {
			args->consdev->cn_dev = dev;
			cn_tab->cn_pollc = args->consdev->cn_pollc;
			cn_tab->cn_getc = args->consdev->cn_getc;
		}
		cn_tab->cn_dev = dev;
	}
	if ((zst->zst_hwflags & ZS_HWFLAG_CONSOLE_OUTPUT) != 0) {
		o = " output";
		if ((args->hwflags & ZS_HWFLAG_USE_CONSDEV) != 0) {
			cn_tab->cn_putc = args->consdev->cn_putc;
		}
		cn_tab->cn_dev = dev;
	}
	if (i != NULL || o != NULL) {
		printf(": console%s", i ? (o ? "" : i) : o);
	}

#ifdef KGDB
	if (zs_check_kgdb(cs, dev)) {
		/*
		 * Allow kgdb to "take over" this port.  Returns true
		 * if this serial port is in-use by kgdb.
		 */
		printf(": kgdb\n");
		/*
		 * This is the kgdb port (exclusive use)
		 * so skip the normal attach code.
		 */
		return;
	}
#endif

#if defined(__sparc__) || defined(__sparc64__)
	if (strcmp(args->type, "keyboard") == 0 ||
	    strcmp(args->type, "mouse") == 0)
		printf(": %s", args->type);
#endif

	printf("\n");

	tp = ttymalloc(0);
	tp->t_dev = dev;
	tp->t_oproc = zsstart;
	tp->t_param = zsparam;
	tp->t_hwiflow = zshwiflow;

	zst->zst_tty = tp;
	zst->zst_rbuf = mallocarray(zstty_rbuf_size, 2, M_DEVBUF, M_WAITOK);
	zst->zst_ebuf = zst->zst_rbuf + (zstty_rbuf_size * 2);
	/* Disable the high water mark. */
	zst->zst_r_hiwat = 0;
	zst->zst_r_lowat = 0;
	zst->zst_rbget = zst->zst_rbput = zst->zst_rbuf;
	zst->zst_rbavail = zstty_rbuf_size;

	/* if there are no enable/disable functions, assume the device
	   is always enabled */
	if (!cs->enable)
		cs->enabled = 1;

	/*
	 * Hardware init
	 */
	dtr_on = 0;
	resetbit = 0;
	if (ISSET(zst->zst_hwflags, ZS_HWFLAG_CONSOLE)) {
		/* Call zsparam similar to open. */
		struct termios t;

		/* Wait a while for previous console output to complete */
		DELAY(10000);

		/* Setup the "new" parameters in t. */
		t.c_ispeed = 0;
		t.c_ospeed = cs->cs_defspeed;
		t.c_cflag = cs->cs_defcflag;

		s = splzs();

		/*
		 * Turn on receiver and status interrupts.
		 * We defer the actual write of the register to zsparam(),
		 * but we must make sure status interrupts are turned on by
		 * the time zsparam() reads the initial rr0 state.
		 */
		SET(cs->cs_preg[1], ZSWR1_RIE | ZSWR1_TIE | ZSWR1_SIE);

		splx(s);

		/* Make sure zsparam will see changes. */
		tp->t_ospeed = 0;
		(void)zsparam(tp, &t);

		/* Make sure DTR is on now. */
		dtr_on = 1;
	} else if (!ISSET(zst->zst_hwflags, ZS_HWFLAG_NORESET)) {
		/* Not the console; may need reset. */
		resetbit = (channel == 0) ? ZSWR9_A_RESET : ZSWR9_B_RESET;
	}

	s = splzs();
	if (resetbit)
		zs_write_reg(cs, 9, resetbit);
	zs_modem(zst, dtr_on);
	splx(s);
}


/*
 * Return pointer to our tty.
 */
struct tty *
zstty(dev_t dev)
{
	struct zstty_softc *zst = zs_device_lookup(&zstty_cd, ZSUNIT(dev));

	return (zst->zst_tty);
}


void
zs_shutdown(struct zstty_softc *zst)
{
	struct zs_chanstate *cs = zst->zst_cs;
	struct tty *tp = zst->zst_tty;
	int s;

	s = splzs();

	/* If we were asserting flow control, then deassert it. */
	SET(zst->zst_rx_flags, RX_IBUF_BLOCKED);
	zs_hwiflow(zst);

	/* Clear any break condition set with TIOCSBRK. */
	zs_break(cs, 0);

	/* Turn off PPS capture on last close. */
	zst->zst_ppsmask = 0;

	/*
	 * Hang up if necessary.  Wait a bit, so the other side has time to
	 * notice even if we immediately open the port again.
	 */
	if (ISSET(tp->t_cflag, HUPCL) || ISSET(tp->t_state, TS_WOPEN)) {
		zs_modem(zst, 0);
		/* hold low for 1 second */
		(void)tsleep(cs, TTIPRI, ttclos, hz);
	}

	/* Turn off interrupts if not the console. */
	if (!ISSET(zst->zst_hwflags, ZS_HWFLAG_CONSOLE)) {
		CLR(cs->cs_preg[1], ZSWR1_RIE | ZSWR1_TIE | ZSWR1_SIE);
		cs->cs_creg[1] = cs->cs_preg[1];
		zs_write_reg(cs, 1, cs->cs_creg[1]);
	}

	/* Call the power management hook. */
	if (cs->disable) {
#ifdef DIAGNOSTIC
		if (!cs->enabled)
			panic("%s: not enabled?", __func__);
#endif
		(*cs->disable)(zst->zst_cs);
	}

	splx(s);
}

/*
 * Open a zs serial (tty) port.
 */
int
zsopen(dev_t dev, int flags, int mode, struct proc *p)
{
	struct zstty_softc *zst;
	struct zs_chanstate *cs;
	struct tty *tp;
	int s;
#if IPL_ZS != IPL_TTY
	int s2;
#endif
	int error;

	zst = zs_device_lookup(&zstty_cd, ZSUNIT(dev));
	if (zst == NULL)
		return (ENXIO);

	tp = zst->zst_tty;
	cs = zst->zst_cs;

	/* If KGDB took the line, then tp==NULL */
	if (tp == NULL)
		return (EBUSY);

	if (ISSET(tp->t_state, TS_ISOPEN) &&
	    ISSET(tp->t_state, TS_XCLUDE) &&
	    suser(p, 0) != 0)
		return (EBUSY);

	s = spltty();

	/*
	 * Do the following iff this is a first open.
	 */
	if (!ISSET(tp->t_state, TS_ISOPEN)) {
		struct termios t;

		tp->t_dev = dev;

		/* Call the power management hook. */
		if (cs->enable) {
			if ((*cs->enable)(cs)) {
				splx(s);
				printf("%s: device enable failed\n",
				    zst->zst_dev.dv_xname);
				return (EIO);
			}
		}

		/*
		 * Initialize the termios status to the defaults.  Add in the
		 * sticky bits from TIOCSFLAGS.
		 */
		t.c_ispeed = 0;
		t.c_ospeed = cs->cs_defspeed;
		t.c_cflag = cs->cs_defcflag;
		if (ISSET(zst->zst_swflags, TIOCFLAG_CLOCAL))
			SET(t.c_cflag, CLOCAL);
		if (ISSET(zst->zst_swflags, TIOCFLAG_CRTSCTS))
			SET(t.c_cflag, CRTSCTS);
		if (ISSET(zst->zst_swflags, TIOCFLAG_MDMBUF))
			SET(t.c_cflag, MDMBUF);

#if IPL_ZS != IPL_TTY
		s2 = splzs();
#endif

		/*
		 * Turn on receiver and status interrupts.
		 * We defer the actual write of the register to zsparam(),
		 * but we must make sure status interrupts are turned on by
		 * the time zsparam() reads the initial rr0 state.
		 */
		SET(cs->cs_preg[1], ZSWR1_RIE | ZSWR1_TIE | ZSWR1_SIE);

		/* Clear PPS capture state on first open. */
		zst->zst_ppsmask = 0;

#if IPL_ZS != IPL_TTY
		splx(s2);
#endif

		/* Make sure zsparam will see changes. */
		tp->t_ospeed = 0;
		(void)zsparam(tp, &t);

		/*
		 * Note: zsparam has done: cflag, ispeed, ospeed
		 * so we just need to do: iflag, oflag, lflag, cc
		 * For "raw" mode, just leave all zeros.
		 */
		if (!ISSET(zst->zst_hwflags, ZS_HWFLAG_RAW)) {
			tp->t_iflag = TTYDEF_IFLAG;
			tp->t_oflag = TTYDEF_OFLAG;
			tp->t_lflag = TTYDEF_LFLAG;
		} else {
			tp->t_iflag = 0;
			tp->t_oflag = 0;
			tp->t_lflag = 0;
		}
		ttychars(tp);
		ttsetwater(tp);

		if (ZSDIALOUT(dev))
			SET(tp->t_state, TS_CARR_ON);
		else
			CLR(tp->t_state, TS_CARR_ON);

#if IPL_ZS != IPL_TTY
		s2 = splzs();
#endif

		/* Clear the input ring, and unblock. */
		zst->zst_rbget = zst->zst_rbput = zst->zst_rbuf;
		zst->zst_rbavail = zstty_rbuf_size;
		zs_iflush(cs);
		CLR(zst->zst_rx_flags, RX_ANY_BLOCK);
		zs_hwiflow(zst);

#if IPL_ZS != IPL_TTY
		splx(s2);
#endif
	}

	if (ZSDIALOUT(dev)) {
		if (ISSET(tp->t_state, TS_ISOPEN)) {
			/* someone already is dialed in... */
			splx(s);
			return EBUSY;
		}
		cs->cs_cua = 1;
	}

	error = 0;
	/* wait for carrier if necessary */
	if (ISSET(flags, O_NONBLOCK)) {
		if (!ZSDIALOUT(dev) && cs->cs_cua) {
			/* Opening TTY non-blocking... but the CUA is busy */
			error = EBUSY;
		}
	} else
	  while (cs->cs_cua ||
	    (!ISSET(tp->t_cflag, CLOCAL) && !ISSET(tp->t_state, TS_CARR_ON))) {
		int rr0;

		error = 0;
		SET(tp->t_state, TS_WOPEN);

		if (!ZSDIALOUT(dev) && !cs->cs_cua) {
			/*
			 * Turn on DTR.  We must always do this on non-CUA
			 * devices, even if carrier is not present, because
			 * otherwise we'd have to use TIOCSDTR immediately
			 * after setting CLOCAL, which applications do not
			 * expect.  We always assert DTR while the device is
			 * open unless explicitly requested to deassert it.
			 */
#if IPL_ZS != IPL_TTY
			s2 = splzs();
#endif
			zs_modem(zst, 1);
			rr0 = zs_read_csr(cs);
#if IPL_ZS != IPL_TTY
			splx(s2);
#endif

			/* loop, turning on the device, until carrier present */
			if (ISSET(rr0, ZSRR0_DCD) ||
			    ISSET(zst->zst_swflags, TIOCFLAG_SOFTCAR))
				SET(tp->t_state, TS_CARR_ON);
		}

		if ((ISSET(tp->t_cflag, CLOCAL) ||
		    ISSET(tp->t_state, TS_CARR_ON)) && !cs->cs_cua)
			break;

		error = ttysleep(tp, (caddr_t)&tp->t_rawq, TTIPRI | PCATCH,
		    ttopen, 0);

		if (!ZSDIALOUT(dev) && cs->cs_cua && error == EINTR) {
			error = 0;
			continue;
		}

		if (error) {
			if (!ISSET(tp->t_state, TS_ISOPEN)) {
#if IPL_ZS != IPL_TTY
				s2 = splzs();
#endif
				zs_modem(zst, 0);
#if IPL_ZS != IPL_TTY
				splx(s2);
#endif
				CLR(tp->t_state, TS_WOPEN);
				ttwakeup(tp);
			}
			if (ZSDIALOUT(dev))
				cs->cs_cua = 0;
			CLR(tp->t_state, TS_WOPEN);
			break;
		}
		if (!ZSDIALOUT(dev) && cs->cs_cua)
			continue;
	}

	splx(s);

	if (error == 0)
		error = ((*linesw[tp->t_line].l_open)(dev, tp, p));
	if (error)
		goto bad;

	return (0);

bad:
	if (!ISSET(tp->t_state, TS_ISOPEN)) {
		/*
		 * We failed to open the device, and nobody else had it opened.
		 * Clean up the state as appropriate.
		 */
		zs_shutdown(zst);
	}

	return (error);
}

/*
 * Close a zs serial port.
 */
int
zsclose(dev_t dev, int flags, int mode, struct proc *p)
{
	struct zstty_softc *zst = zs_device_lookup(&zstty_cd, ZSUNIT(dev));
	struct zs_chanstate *cs = zst->zst_cs;
	struct tty *tp = zst->zst_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, flags, p);

	s = spltty();
	cs->cs_cua = 0;
	ttyclose(tp);
	splx(s);

	if (!ISSET(tp->t_state, TS_ISOPEN)) {
		/*
		 * Although we got a last close, the device may still be in
		 * use; e.g. if this was the dialout node, and there are still
		 * processes waiting for carrier on the non-dialout node.
		 */
		zs_shutdown(zst);
	}

	return (0);
}

/*
 * Read/write zs serial port.
 */
int
zsread(dev_t dev, struct uio *uio, int flags)
{
	struct zstty_softc *zst = zs_device_lookup(&zstty_cd, ZSUNIT(dev));
	struct tty *tp = zst->zst_tty;

	return (*linesw[tp->t_line].l_read)(tp, uio, flags);
}

int
zswrite(dev_t dev, struct uio *uio, int flags)
{
	struct zstty_softc *zst = zs_device_lookup(&zstty_cd, ZSUNIT(dev));
	struct tty *tp = zst->zst_tty;

	return (*linesw[tp->t_line].l_write)(tp, uio, flags);
}

int
zsioctl(dev_t dev, u_long cmd, caddr_t data, int flag, struct proc *p)
{
	struct zstty_softc *zst = zs_device_lookup(&zstty_cd, ZSUNIT(dev));
	struct zs_chanstate *cs = zst->zst_cs;
	struct tty *tp = zst->zst_tty;
	int error;
	int s;

	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);

#ifdef	ZS_MD_IOCTL
	error = ZS_MD_IOCTL;
	if (error >= 0)
		return (error);
#endif	/* ZS_MD_IOCTL */

	error = 0;

	s = splzs();

	switch (cmd) {
	case TIOCSBRK:
		zs_break(cs, 1);
		break;

	case TIOCCBRK:
		zs_break(cs, 0);
		break;

	case TIOCGFLAGS:
		*(int *)data = zst->zst_swflags;
		break;

	case TIOCSFLAGS:
		error = suser(p, 0);
		if (error)
			break;
		zst->zst_swflags = *(int *)data;
		if (ISSET(zst->zst_hwflags, ZS_HWFLAG_NO_DCD))
			SET(zst->zst_swflags, TIOCFLAG_SOFTCAR);
		break;

	case TIOCSDTR:
		zs_modem(zst, 1);
		break;

	case TIOCCDTR:
		zs_modem(zst, 0);
		break;

	case TIOCMSET:
	case TIOCMBIS:
	case TIOCMBIC:
		tiocm_to_zs(zst, cmd, *(int *)data);
		break;

	case TIOCMGET:
		*(int *)data = zs_to_tiocm(zst);
		break;

	default:
		error = ENOTTY;
		break;
	}

	splx(s);

	return (error);
}

/*
 * Start or restart transmission.
 */
void
zsstart(struct tty *tp)
{
	struct zstty_softc *zst = zs_device_lookup(&zstty_cd, ZSUNIT(tp->t_dev));
	struct zs_chanstate *cs = zst->zst_cs;
	u_char *tba;
	int tbc, rr0;
	int s;

	s = spltty();
	if (ISSET(tp->t_state, TS_BUSY | TS_TIMEOUT | TS_TTSTOP))
		goto out;
	if (zst->zst_tx_stopped)
		goto out;

	ttwakeupwr(tp);
	if (tp->t_outq.c_cc == 0)
		goto out;

	/* Grab the first contiguous region of buffer space. */
	tba = tp->t_outq.c_cf;
	tbc = ndqb(&tp->t_outq, 0);

#if IPL_ZS != IPL_TTY
	(void)splzs();
#endif

	zst->zst_tba = tba;
	zst->zst_tbc = tbc;
	SET(tp->t_state, TS_BUSY);
	zst->zst_tx_busy = 1;

	do {
		rr0 = zs_read_csr(cs);
		if ((rr0 & ZSRR0_TX_READY) == 0)
			break;

		zs_write_data(cs, *zst->zst_tba);
		zst->zst_tbc--;
		zst->zst_tba++;
	} while (zst->zst_tbc > 0);

out:
	splx(s);
}

/*
 * Stop output, e.g., for ^S or output flush.
 */
int
zsstop(struct tty *tp, int flag)
{
	struct zstty_softc *zst = zs_device_lookup(&zstty_cd, ZSUNIT(tp->t_dev));
	int s;

	s = splzs();
	if (ISSET(tp->t_state, TS_BUSY)) {
		/* Stop transmitting at the next chunk. */
		zst->zst_tbc = 0;
		zst->zst_heldtbc = 0;
		if (!ISSET(tp->t_state, TS_TTSTOP))
			SET(tp->t_state, TS_FLUSH);
	}
	splx(s);
	return 0;
}

/*
 * Set ZS tty parameters from termios.
 * XXX - Should just copy the whole termios after
 * making sure all the changes could be done.
 */
int
zsparam(struct tty *tp, struct termios *t)
{
	struct zstty_softc *zst = zs_device_lookup(&zstty_cd, ZSUNIT(tp->t_dev));
	struct zs_chanstate *cs = zst->zst_cs;
	int ospeed;
	tcflag_t cflag;
	uint8_t tmp3, tmp4, tmp5;
	int s, error;

	ospeed = t->c_ospeed;
	cflag = t->c_cflag;

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

	/*
	 * For the console, always force CLOCAL and !HUPCL, so that the port
	 * is always active.
	 */
	if (ISSET(zst->zst_swflags, TIOCFLAG_SOFTCAR) ||
	    ISSET(zst->zst_hwflags, ZS_HWFLAG_CONSOLE)) {
		SET(cflag, CLOCAL);
		CLR(cflag, HUPCL);
	}

	/*
	 * Only whack the UART when params change.
	 * Some callers need to clear tp->t_ospeed
	 * to make sure initialization gets done.
	 */
	if (tp->t_ospeed == ospeed &&
	    tp->t_cflag == cflag)
		return (0);

	/*
	 * Call MD functions to deal with changed
	 * clock modes or H/W flow control modes.
	 * The BRG divisor is set now. (reg 12,13)
	 */
	error = zs_set_speed(cs, ospeed);
	if (error)
		return (error);
	error = zs_set_modes(cs, cflag);
	if (error)
		return (error);

	/*
	 * Block interrupts so that state will not
	 * be altered until we are done setting it up.
	 *
	 * Initial values in cs_preg are set before
	 * our attach routine is called.  The master
	 * interrupt enable is handled by zsc.c
	 *
	 */
	s = splzs();

	/*
	 * Recalculate which status ints to enable.
	 */
	zs_maskintr(zst);

	/* Recompute character size bits. */
	tmp3 = cs->cs_preg[3];
	tmp5 = cs->cs_preg[5];
	CLR(tmp3, ZSWR3_RXSIZE);
	CLR(tmp5, ZSWR5_TXSIZE);
	switch (ISSET(cflag, CSIZE)) {
	case CS5:
		SET(tmp3, ZSWR3_RX_5);
		SET(tmp5, ZSWR5_TX_5);
		break;
	case CS6:
		SET(tmp3, ZSWR3_RX_6);
		SET(tmp5, ZSWR5_TX_6);
		break;
	case CS7:
		SET(tmp3, ZSWR3_RX_7);
		SET(tmp5, ZSWR5_TX_7);
		break;
	case CS8:
		SET(tmp3, ZSWR3_RX_8);
		SET(tmp5, ZSWR5_TX_8);
		break;
	}
	cs->cs_preg[3] = tmp3;
	cs->cs_preg[5] = tmp5;

	/*
	 * Recompute the stop bits and parity bits.  Note that
	 * zs_set_speed() may have set clock selection bits etc.
	 * in wr4, so those must preserved.
	 */
	tmp4 = cs->cs_preg[4];
	CLR(tmp4, ZSWR4_SBMASK | ZSWR4_PARMASK);
	if (ISSET(cflag, CSTOPB))
		SET(tmp4, ZSWR4_TWOSB);
	else
		SET(tmp4, ZSWR4_ONESB);
	if (!ISSET(cflag, PARODD))
		SET(tmp4, ZSWR4_EVENP);
	if (ISSET(cflag, PARENB))
		SET(tmp4, ZSWR4_PARENB);
	cs->cs_preg[4] = tmp4;

	/* And copy to tty. */
	tp->t_ispeed = 0;
	tp->t_ospeed = ospeed;
	tp->t_cflag = cflag;

	/*
	 * If nothing is being transmitted, set up new current values,
	 * else mark them as pending.
	 */
	if (!cs->cs_heldchange) {
		if (zst->zst_tx_busy) {
			zst->zst_heldtbc = zst->zst_tbc;
			zst->zst_tbc = 0;
			cs->cs_heldchange = 1;
		} else
			zs_loadchannelregs(cs);
	}

	/*
	 * If hardware flow control is disabled, turn off the buffer water
	 * marks and unblock any soft flow control state.  Otherwise, enable
	 * the water marks.
	 */
	if (!ISSET(cflag, CHWFLOW)) {
		zst->zst_r_hiwat = 0;
		zst->zst_r_lowat = 0;
		if (ISSET(zst->zst_rx_flags, RX_TTY_OVERFLOWED)) {
			CLR(zst->zst_rx_flags, RX_TTY_OVERFLOWED);
			zst->zst_rx_ready = 1;
			cs->cs_softreq = 1;
		}
		if (ISSET(zst->zst_rx_flags, RX_TTY_BLOCKED|RX_IBUF_BLOCKED)) {
			CLR(zst->zst_rx_flags, RX_TTY_BLOCKED|RX_IBUF_BLOCKED);
			zs_hwiflow(zst);
		}
	} else {
		zst->zst_r_hiwat = zstty_rbuf_hiwat;
		zst->zst_r_lowat = zstty_rbuf_lowat;
	}

	/*
	 * Force a recheck of the hardware carrier and flow control status,
	 * since we may have changed which bits we're looking at.
	 */
	zstty_stint(cs, 1);

	splx(s);

	/*
	 * If hardware flow control is disabled, unblock any hard flow control
	 * state.
	 */
	if (!ISSET(cflag, CHWFLOW)) {
		if (zst->zst_tx_stopped) {
			zst->zst_tx_stopped = 0;
			zsstart(tp);
		}
	}

	zstty_softint(cs);

	return (0);
}

/*
 * Compute interrupt enable bits and set in the pending bits. Called both
 * in zsparam() and when PPS (pulse per second timing) state changes.
 * Must be called at splzs().
 */
void
zs_maskintr(struct zstty_softc *zst)
{
	struct zs_chanstate *cs = zst->zst_cs;
	uint8_t tmp15;

	cs->cs_rr0_mask = cs->cs_rr0_cts | cs->cs_rr0_dcd;
	if (zst->zst_ppsmask != 0)
		cs->cs_rr0_mask |= cs->cs_rr0_pps;
	tmp15 = cs->cs_preg[15];
	if (ISSET(cs->cs_rr0_mask, ZSRR0_DCD))
		SET(tmp15, ZSWR15_DCD_IE);
	else
		CLR(tmp15, ZSWR15_DCD_IE);
	if (ISSET(cs->cs_rr0_mask, ZSRR0_CTS))
		SET(tmp15, ZSWR15_CTS_IE);
	else
		CLR(tmp15, ZSWR15_CTS_IE);
	cs->cs_preg[15] = tmp15;
}


/*
 * Raise or lower modem control (DTR/RTS) signals.  If a character is
 * in transmission, the change is deferred.
 * Called at splzs().
 */
void
zs_modem(struct zstty_softc *zst, int onoff)
{
	struct zs_chanstate *cs = zst->zst_cs, *ccs;

	if (cs->cs_wr5_dtr == 0)
		return;

	ccs = (cs->cs_ctl_chan != NULL ? cs->cs_ctl_chan : cs);

	if (onoff)
		SET(ccs->cs_preg[5], cs->cs_wr5_dtr);
	else
		CLR(ccs->cs_preg[5], cs->cs_wr5_dtr);

	if (!cs->cs_heldchange) {
		if (zst->zst_tx_busy) {
			zst->zst_heldtbc = zst->zst_tbc;
			zst->zst_tbc = 0;
			cs->cs_heldchange = 1;
		} else
			zs_loadchannelregs(cs);
	}
}

/*
 * Set modem bits.
 * Called at splzs().
 */
void
tiocm_to_zs(struct zstty_softc *zst, u_long how, int ttybits)
{
	struct zs_chanstate *cs = zst->zst_cs, *ccs;
	uint8_t zsbits;

	ccs = (cs->cs_ctl_chan != NULL ? cs->cs_ctl_chan : cs);

	zsbits = 0;
	if (ISSET(ttybits, TIOCM_DTR))
		SET(zsbits, ZSWR5_DTR);
	if (ISSET(ttybits, TIOCM_RTS))
		SET(zsbits, ZSWR5_RTS);

	switch (how) {
	case TIOCMBIC:
		CLR(ccs->cs_preg[5], zsbits);
		break;

	case TIOCMBIS:
		SET(ccs->cs_preg[5], zsbits);
		break;

	case TIOCMSET:
		CLR(ccs->cs_preg[5], ZSWR5_RTS | ZSWR5_DTR);
		SET(ccs->cs_preg[5], zsbits);
		break;
	}

	if (!cs->cs_heldchange) {
		if (zst->zst_tx_busy) {
			zst->zst_heldtbc = zst->zst_tbc;
			zst->zst_tbc = 0;
			cs->cs_heldchange = 1;
		} else
			zs_loadchannelregs(cs);
	}
}

/*
 * Get modem bits.
 * Called at splzs().
 */
int
zs_to_tiocm(struct zstty_softc *zst)
{
	struct zs_chanstate *cs = zst->zst_cs, *ccs;
	uint8_t zsbits;
	int ttybits = 0;

	ccs = (cs->cs_ctl_chan != NULL ? cs->cs_ctl_chan : cs);

	zsbits = ccs->cs_preg[5];
	if (ISSET(zsbits, ZSWR5_DTR))
		SET(ttybits, TIOCM_DTR);
	if (ISSET(zsbits, ZSWR5_RTS))
		SET(ttybits, TIOCM_RTS);

	zsbits = cs->cs_rr0;
	if (ISSET(zsbits, ZSRR0_DCD))
		SET(ttybits, TIOCM_CD);
	if (ISSET(zsbits, ZSRR0_CTS))
		SET(ttybits, TIOCM_CTS);

	return (ttybits);
}

/*
 * Try to block or unblock input using hardware flow-control.
 * This is called by kern/tty.c if MDMBUF|CRTSCTS is set, and
 * if this function returns non-zero, the TS_TBLOCK flag will
 * be set or cleared according to the "block" arg passed.
 */
int
zshwiflow(struct tty *tp, int block)
{
	struct zstty_softc *zst = zs_device_lookup(&zstty_cd, ZSUNIT(tp->t_dev));
	struct zs_chanstate *cs = zst->zst_cs;
	int s;

	if (cs->cs_wr5_rts == 0)
		return (0);

	s = splzs();
	if (block) {
		if (!ISSET(zst->zst_rx_flags, RX_TTY_BLOCKED)) {
			SET(zst->zst_rx_flags, RX_TTY_BLOCKED);
			zs_hwiflow(zst);
		}
	} else {
		if (ISSET(zst->zst_rx_flags, RX_TTY_OVERFLOWED)) {
			CLR(zst->zst_rx_flags, RX_TTY_OVERFLOWED);
			zst->zst_rx_ready = 1;
			cs->cs_softreq = 1;
		}
		if (ISSET(zst->zst_rx_flags, RX_TTY_BLOCKED)) {
			CLR(zst->zst_rx_flags, RX_TTY_BLOCKED);
			zs_hwiflow(zst);
		}
	}
	splx(s);
	return (1);
}

/*
 * Internal version of zshwiflow
 * Called at splzs()
 */
void
zs_hwiflow(struct zstty_softc *zst)
{
	struct zs_chanstate *cs = zst->zst_cs, *ccs;

	if (cs->cs_wr5_rts == 0)
		return;

	ccs = (cs->cs_ctl_chan != NULL ? cs->cs_ctl_chan : cs);

	if (ISSET(zst->zst_rx_flags, RX_ANY_BLOCK)) {
		CLR(ccs->cs_preg[5], cs->cs_wr5_rts);
		CLR(ccs->cs_creg[5], cs->cs_wr5_rts);
	} else {
		SET(ccs->cs_preg[5], cs->cs_wr5_rts);
		SET(ccs->cs_creg[5], cs->cs_wr5_rts);
	}
	zs_write_reg(ccs, 5, ccs->cs_creg[5]);
}


/****************************************************************
 * Interface to the lower layer (zscc)
 ****************************************************************/

void zstty_rxsoft(struct zstty_softc *, struct tty *);
void zstty_txsoft(struct zstty_softc *, struct tty *);
void zstty_stsoft(struct zstty_softc *, struct tty *);
void zstty_diag(void *);

/*
 * Receiver Ready interrupt.
 * Called at splzs().
 */
void
zstty_rxint(struct zs_chanstate *cs)
{
	struct zstty_softc *zst = cs->cs_private;
	uint8_t *put, *end;
	u_int cc;
	uint8_t rr0, rr1, c;

	end = zst->zst_ebuf;
	put = zst->zst_rbput;
	cc = zst->zst_rbavail;

	while (cc > 0) {
		/*
		 * First read the status, because reading the received char
		 * destroys the status of this char.
		 */
		rr1 = zs_read_reg(cs, 1);
		c = zs_read_data(cs);

		if (ISSET(rr1, ZSRR1_FE | ZSRR1_DO | ZSRR1_PE)) {
			/* Clear the receive error. */
			zs_write_csr(cs, ZSWR0_RESET_ERRORS);
		}

		put[0] = c;
		put[1] = rr1;
		put += 2;
		if (put >= end)
			put = zst->zst_rbuf;
		cc--;

		rr0 = zs_read_csr(cs);
		if (!ISSET(rr0, ZSRR0_RX_READY))
			break;
	}

	/*
	 * Current string of incoming characters ended because
	 * no more data was available or we ran out of space.
	 * Schedule a receive event if any data was received.
	 * If we're out of space, turn off receive interrupts.
	 */
	zst->zst_rbput = put;
	zst->zst_rbavail = cc;
	if (!ISSET(zst->zst_rx_flags, RX_TTY_OVERFLOWED)) {
		zst->zst_rx_ready = 1;
		cs->cs_softreq = 1;
	}

	/*
	 * See if we are in danger of overflowing a buffer. If
	 * so, use hardware flow control to ease the pressure.
	 */
	if (!ISSET(zst->zst_rx_flags, RX_IBUF_BLOCKED) &&
	    cc < zst->zst_r_hiwat) {
		SET(zst->zst_rx_flags, RX_IBUF_BLOCKED);
		zs_hwiflow(zst);
	}

	/*
	 * If we're out of space, disable receive interrupts
	 * until the queue has drained a bit.
	 */
	if (!cc) {
		SET(zst->zst_rx_flags, RX_IBUF_OVERFLOWED);
		CLR(cs->cs_preg[1], ZSWR1_RIE);
		cs->cs_creg[1] = cs->cs_preg[1];
		zs_write_reg(cs, 1, cs->cs_creg[1]);
	}
}

/*
 * Transmitter Ready interrupt.
 * Called at splzs().
 */
void
zstty_txint(struct zs_chanstate *cs)
{
	struct zstty_softc *zst = cs->cs_private;
	int rr0;

	zs_write_csr(cs, ZSWR0_RESET_TXINT);

	/*
	 * If we've delayed a parameter change, do it now, and restart
	 * output.
	 */
	if (cs->cs_heldchange) {
		zs_loadchannelregs(cs);
		cs->cs_heldchange = 0;
		zst->zst_tbc = zst->zst_heldtbc;
		zst->zst_heldtbc = 0;
	}

	while (zst->zst_tbc > 0) {
		rr0 = zs_read_csr(cs);
		if ((rr0 & ZSRR0_TX_READY) == 0)
			break;

		zs_write_data(cs, *zst->zst_tba);
		zst->zst_tbc--;
		zst->zst_tba++;
	}

	if (zst->zst_tbc == 0) {
		if (zst->zst_tx_busy) {
			zst->zst_tx_busy = 0;
			zst->zst_tx_done = 1;
			cs->cs_softreq = 1;
		}
	}
}

#ifdef DDB
#include <ddb/db_var.h>
#define	DB_CONSOLE	db_console
#else
#define	DB_CONSOLE	0
#endif

/*
 * Status Change interrupt.
 * Called at splzs().
 */
void
zstty_stint(struct zs_chanstate *cs, int force)
{
	struct zstty_softc *zst = cs->cs_private;
	struct tty *tp = zst->zst_tty;
	uint8_t rr0, delta;

	rr0 = zs_read_csr(cs);
	zs_write_csr(cs, ZSWR0_RESET_STATUS);

	/*
	 * Check here for console break, so that we can abort
	 * even when interrupts are locking up the machine.
	 */
	if ((zst->zst_hwflags & ZS_HWFLAG_CONSOLE_INPUT) &&
	    ISSET(rr0, ZSRR0_BREAK) && DB_CONSOLE)
		zs_abort(cs);

	if (!force)
		delta = rr0 ^ cs->cs_rr0;
	else
		delta = cs->cs_rr0_mask;

	ttytstamp(tp, cs->cs_rr0 & ZSRR0_CTS, rr0 & ZSRR0_CTS,
	    cs->cs_rr0 & ZSRR0_DCD, rr0 & ZSRR0_DCD);

	cs->cs_rr0 = rr0;

	if (ISSET(delta, cs->cs_rr0_mask)) {
		SET(cs->cs_rr0_delta, delta);

		/*
		 * Stop output immediately if we lose the output
		 * flow control signal or carrier detect.
		 */
		if (ISSET(~rr0, cs->cs_rr0_mask)) {
			zst->zst_tbc = 0;
			zst->zst_heldtbc = 0;
		}

		zst->zst_st_check = 1;
		cs->cs_softreq = 1;
	}
}

void
zstty_diag(void *arg)
{
	struct zstty_softc *zst = arg;
	int overflows, floods;
	int s;

	s = splzs();
	overflows = zst->zst_overflows;
	zst->zst_overflows = 0;
	floods = zst->zst_floods;
	zst->zst_floods = 0;
	zst->zst_errors = 0;
	splx(s);

	log(LOG_WARNING, "%s: %d silo overflow%s, %d ibuf flood%s\n",
	    zst->zst_dev.dv_xname,
	    overflows, overflows == 1 ? "" : "s",
	    floods, floods == 1 ? "" : "s");
}

void
zstty_rxsoft(struct zstty_softc *zst, struct tty *tp)
{
	struct zs_chanstate *cs = zst->zst_cs;
	int (*rint)(int, struct tty *) = linesw[tp->t_line].l_rint;
	uint8_t *get, *end;
	u_int cc, scc;
	uint8_t rr1;
	int code;
	int s;

	end = zst->zst_ebuf;
	get = zst->zst_rbget;
	scc = cc = zstty_rbuf_size - zst->zst_rbavail;

	if (cc == zstty_rbuf_size) {
		zst->zst_floods++;
		if (zst->zst_errors++ == 0)
			timeout_add_sec(&zst->zst_diag_ch, 60);
	}

	/* If not yet open, drop the entire buffer content here */
	if (!ISSET(tp->t_state, TS_ISOPEN)) {
		get += cc << 1;
		if (get >= end)
			get -= zstty_rbuf_size << 1;
		cc = 0;
	}
	while (cc) {
		code = get[0];
		rr1 = get[1];
		if (ISSET(rr1, ZSRR1_DO | ZSRR1_FE | ZSRR1_PE)) {
			if (ISSET(rr1, ZSRR1_DO)) {
				zst->zst_overflows++;
				if (zst->zst_errors++ == 0)
					timeout_add_sec(&zst->zst_diag_ch, 60);
			}
			if (ISSET(rr1, ZSRR1_FE))
				SET(code, TTY_FE);
			if (ISSET(rr1, ZSRR1_PE))
				SET(code, TTY_PE);
		}
		if ((*rint)(code, tp) == -1) {
			/*
			 * The line discipline's buffer is out of space.
			 */
			if (!ISSET(zst->zst_rx_flags, RX_TTY_BLOCKED)) {
				/*
				 * We're either not using flow control, or the
				 * line discipline didn't tell us to block for
				 * some reason.  Either way, we have no way to
				 * know when there's more space available, so
				 * just drop the rest of the data.
				 */
				get += cc << 1;
				if (get >= end)
					get -= zstty_rbuf_size << 1;
				cc = 0;
			} else {
				/*
				 * Don't schedule any more receive processing
				 * until the line discipline tells us there's
				 * space available (through comhwiflow()).
				 * Leave the rest of the data in the input
				 * buffer.
				 */
				SET(zst->zst_rx_flags, RX_TTY_OVERFLOWED);
			}
			break;
		}
		get += 2;
		if (get >= end)
			get = zst->zst_rbuf;
		cc--;
	}

	if (cc != scc) {
		zst->zst_rbget = get;
		s = splzs();
		cc = zst->zst_rbavail += scc - cc;
		/* Buffers should be ok again, release possible block. */
		if (cc >= zst->zst_r_lowat) {
			if (ISSET(zst->zst_rx_flags, RX_IBUF_OVERFLOWED)) {
				CLR(zst->zst_rx_flags, RX_IBUF_OVERFLOWED);
				SET(cs->cs_preg[1], ZSWR1_RIE);
				cs->cs_creg[1] = cs->cs_preg[1];
				zs_write_reg(cs, 1, cs->cs_creg[1]);
			}
			if (ISSET(zst->zst_rx_flags, RX_IBUF_BLOCKED)) {
				CLR(zst->zst_rx_flags, RX_IBUF_BLOCKED);
				zs_hwiflow(zst);
			}
		}
		splx(s);
	}
}

void
zstty_txsoft(struct zstty_softc *zst, struct tty *tp)
{
	int s;

	CLR(tp->t_state, TS_BUSY);
	if (ISSET(tp->t_state, TS_FLUSH))
		CLR(tp->t_state, TS_FLUSH);
	else {
		s = splzs();
		ndflush(&tp->t_outq, (int)(zst->zst_tba - tp->t_outq.c_cf));
		splx(s);
	}
	(*linesw[tp->t_line].l_start)(tp);
}

void
zstty_stsoft(struct zstty_softc *zst, struct tty *tp)
{
	struct zs_chanstate *cs = zst->zst_cs;
	uint8_t rr0, delta;
	int s;

	s = splzs();
	rr0 = cs->cs_rr0;
	delta = cs->cs_rr0_delta;
	cs->cs_rr0_delta = 0;
	splx(s);

	if (ISSET(delta, cs->cs_rr0_dcd)) {
		/*
		 * Inform the tty layer that carrier detect changed.
		 */
		(void)(*linesw[tp->t_line].l_modem)(tp, ISSET(rr0, ZSRR0_DCD));
	}

	if (ISSET(delta, cs->cs_rr0_cts)) {
		/* Block or unblock output according to flow control. */
		if (ISSET(rr0, cs->cs_rr0_cts)) {
			zst->zst_tx_stopped = 0;
			(*linesw[tp->t_line].l_start)(tp);
		} else {
			zst->zst_tx_stopped = 1;
		}
	}
}

/*
 * Software interrupt.  Called at zssoft
 *
 * The main job to be done here is to empty the input ring
 * by passing its contents up to the tty layer.  The ring is
 * always emptied during this operation, therefore the ring
 * must not be larger than the space after "high water" in
 * the tty layer, or the tty layer might drop our input.
 *
 * Note: an "input blockage" condition is assumed to exist if
 * EITHER the TS_TBLOCK flag or zst_rx_blocked flag is set.
 */
void
zstty_softint(struct zs_chanstate *cs)
{
	struct zstty_softc *zst = cs->cs_private;
	struct tty *tp = zst->zst_tty;
	int s;

	s = spltty();

	if (zst->zst_rx_ready) {
		zst->zst_rx_ready = 0;
		zstty_rxsoft(zst, tp);
	}

	if (zst->zst_st_check) {
		zst->zst_st_check = 0;
		zstty_stsoft(zst, tp);
	}

	if (zst->zst_tx_done) {
		zst->zst_tx_done = 0;
		zstty_txsoft(zst, tp);
	}

	splx(s);
}

struct zsops zsops_tty = {
	zstty_rxint,	/* receive char available */
	zstty_stint,	/* external/status */
	zstty_txint,	/* xmit buffer empty */
	zstty_softint,	/* process software interrupt */
};
