Adding tty support files from FREEBSD tree

4 files changed, 4460 insertions, 0 deletions

diff --git a/freebsd/sys/kern/tty.c b/freebsd/sys/kern/tty.c
new file mode 100644
index 00000000..95afaebc
--- /dev/null
+++ b/freebsd/sys/kern/tty.c
@@ -0,0 +1,2349 @@
+#include <machine/rtems-bsd-kernel-space.h>
+
+/*-
+ * Copyright (c) 2008 Ed Schouten <ed@FreeBSD.org>
+ * All rights reserved.
+ *
+ * Portions of this software were developed under sponsorship from Snow
+ * B.V., the Netherlands.
+ *
+ * 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.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <rtems/bsd/local/opt_capsicum.h>
+#include <rtems/bsd/local/opt_compat.h>
+
+#include <rtems/bsd/sys/param.h>
+#include <sys/capsicum.h>
+#include <sys/conf.h>
+#include <sys/cons.h>
+#include <sys/fcntl.h>
+#include <sys/file.h>
+#include <sys/filedesc.h>
+#include <sys/filio.h>
+#ifdef COMPAT_43TTY
+#include <sys/ioctl_compat.h>
+#endif /* COMPAT_43TTY */
+#include <sys/kernel.h>
+#include <sys/limits.h>
+#include <sys/malloc.h>
+#include <sys/mount.h>
+#include <sys/poll.h>
+#include <sys/priv.h>
+#include <sys/proc.h>
+#include <sys/serial.h>
+#include <sys/signal.h>
+#include <sys/stat.h>
+#include <sys/sx.h>
+#include <sys/sysctl.h>
+#include <sys/systm.h>
+#include <sys/tty.h>
+#include <sys/ttycom.h>
+#define TTYDEFCHARS
+#include <sys/ttydefaults.h>
+#undef TTYDEFCHARS
+#include <sys/ucred.h>
+#include <sys/vnode.h>
+
+#include <machine/stdarg.h>
+
+static MALLOC_DEFINE(M_TTY, "tty", "tty device");
+
+static void tty_rel_free(struct tty *tp);
+
+static TAILQ_HEAD(, tty) tty_list = TAILQ_HEAD_INITIALIZER(tty_list);
+static struct sx tty_list_sx;
+SX_SYSINIT(tty_list, &tty_list_sx, "tty list");
+static unsigned int tty_list_count = 0;
+
+/* Character device of /dev/console. */
+static struct cdev	*dev_console;
+static const char	*dev_console_filename;
+
+/*
+ * Flags that are supported and stored by this implementation.
+ */
+#define TTYSUP_IFLAG	(IGNBRK|BRKINT|IGNPAR|PARMRK|INPCK|ISTRIP|\
+			INLCR|IGNCR|ICRNL|IXON|IXOFF|IXANY|IMAXBEL)
+#define TTYSUP_OFLAG	(OPOST|ONLCR|TAB3|ONOEOT|OCRNL|ONOCR|ONLRET)
+#define TTYSUP_LFLAG	(ECHOKE|ECHOE|ECHOK|ECHO|ECHONL|ECHOPRT|\
+			ECHOCTL|ISIG|ICANON|ALTWERASE|IEXTEN|TOSTOP|\
+			FLUSHO|NOKERNINFO|NOFLSH)
+#define TTYSUP_CFLAG	(CIGNORE|CSIZE|CSTOPB|CREAD|PARENB|PARODD|\
+			HUPCL|CLOCAL|CCTS_OFLOW|CRTS_IFLOW|CDTR_IFLOW|\
+			CDSR_OFLOW|CCAR_OFLOW)
+
+#define	TTY_CALLOUT(tp,d) (dev2unit(d) & TTYUNIT_CALLOUT)
+
+static int  tty_drainwait = 5 * 60;
+SYSCTL_INT(_kern, OID_AUTO, tty_drainwait, CTLFLAG_RWTUN,
+    &tty_drainwait, 0, "Default output drain timeout in seconds");
+
+/*
+ * Set TTY buffer sizes.
+ */
+
+#define	TTYBUF_MAX	65536
+
+/*
+ * Allocate buffer space if necessary, and set low watermarks, based on speed.
+ * Note that the ttyxxxq_setsize() functions may drop and then reacquire the tty
+ * lock during memory allocation.  They will return ENXIO if the tty disappears
+ * while unlocked.
+ */
+static int
+tty_watermarks(struct tty *tp)
+{
+	size_t bs = 0;
+	int error;
+
+	/* Provide an input buffer for 2 seconds of data. */
+	if (tp->t_termios.c_cflag & CREAD)
+		bs = MIN(tp->t_termios.c_ispeed / 5, TTYBUF_MAX);
+	error = ttyinq_setsize(&tp->t_inq, tp, bs);
+	if (error != 0)
+		return (error);
+
+	/* Set low watermark at 10% (when 90% is available). */
+	tp->t_inlow = (ttyinq_getallocatedsize(&tp->t_inq) * 9) / 10;
+
+	/* Provide an output buffer for 2 seconds of data. */
+	bs = MIN(tp->t_termios.c_ospeed / 5, TTYBUF_MAX);
+	error = ttyoutq_setsize(&tp->t_outq, tp, bs);
+	if (error != 0)
+		return (error);
+
+	/* Set low watermark at 10% (when 90% is available). */
+	tp->t_outlow = (ttyoutq_getallocatedsize(&tp->t_outq) * 9) / 10;
+
+	return (0);
+}
+
+static int
+tty_drain(struct tty *tp, int leaving)
+{
+	sbintime_t timeout_at;
+	size_t bytes;
+	int error;
+
+	if (ttyhook_hashook(tp, getc_inject))
+		/* buffer is inaccessible */
+		return (0);
+
+	/*
+	 * For close(), use the recent historic timeout of "1 second without
+	 * making progress".  For tcdrain(), use t_drainwait as the timeout,
+	 * with zero meaning "no timeout" which gives POSIX behavior.
+	 */
+	if (leaving)
+		timeout_at = getsbinuptime() + SBT_1S;
+	else if (tp->t_drainwait != 0)
+		timeout_at = getsbinuptime() + SBT_1S * tp->t_drainwait;
+	else
+		timeout_at = 0;
+
+	/*
+	 * Poll the output buffer and the hardware for completion, at 10 Hz.
+	 * Polling is required for devices which are not able to signal an
+	 * interrupt when the transmitter becomes idle (most USB serial devs).
+	 * The unusual structure of this loop ensures we check for busy one more
+	 * time after tty_timedwait() returns EWOULDBLOCK, so that success has
+	 * higher priority than timeout if the IO completed in the last 100mS.
+	 */
+	error = 0;
+	bytes = ttyoutq_bytesused(&tp->t_outq);
+	for (;;) {
+		if (ttyoutq_bytesused(&tp->t_outq) == 0 && !ttydevsw_busy(tp))
+			return (0);
+		if (error != 0)
+			return (error);
+		ttydevsw_outwakeup(tp);
+		error = tty_timedwait(tp, &tp->t_outwait, hz / 10);
+		if (error != 0 && error != EWOULDBLOCK)
+			return (error);
+		else if (timeout_at == 0 || getsbinuptime() < timeout_at)
+			error = 0;
+		else if (leaving && ttyoutq_bytesused(&tp->t_outq) < bytes) {
+			/* In close, making progress, grant an extra second. */
+			error = 0;
+			timeout_at += SBT_1S;
+			bytes = ttyoutq_bytesused(&tp->t_outq);
+		}
+	}
+}
+
+/*
+ * Though ttydev_enter() and ttydev_leave() seem to be related, they
+ * don't have to be used together. ttydev_enter() is used by the cdev
+ * operations to prevent an actual operation from being processed when
+ * the TTY has been abandoned. ttydev_leave() is used by ttydev_open()
+ * and ttydev_close() to determine whether per-TTY data should be
+ * deallocated.
+ */
+
+static __inline int
+ttydev_enter(struct tty *tp)
+{
+
+	tty_lock(tp);
+
+	if (tty_gone(tp) || !tty_opened(tp)) {
+		/* Device is already gone. */
+		tty_unlock(tp);
+		return (ENXIO);
+	}
+
+	return (0);
+}
+
+static void
+ttydev_leave(struct tty *tp)
+{
+
+	tty_lock_assert(tp, MA_OWNED);
+
+	if (tty_opened(tp) || tp->t_flags & TF_OPENCLOSE) {
+		/* Device is still opened somewhere. */
+		tty_unlock(tp);
+		return;
+	}
+
+	tp->t_flags |= TF_OPENCLOSE;
+
+	/* Stop asynchronous I/O. */
+	funsetown(&tp->t_sigio);
+
+	/* Remove console TTY. */
+	if (constty == tp)
+		constty_clear();
+
+	/* Drain any output. */
+	if (!tty_gone(tp))
+		tty_drain(tp, 1);
+
+	ttydisc_close(tp);
+
+	/* Free i/o queues now since they might be large. */
+	ttyinq_free(&tp->t_inq);
+	tp->t_inlow = 0;
+	ttyoutq_free(&tp->t_outq);
+	tp->t_outlow = 0;
+
+	knlist_clear(&tp->t_inpoll.si_note, 1);
+	knlist_clear(&tp->t_outpoll.si_note, 1);
+
+	if (!tty_gone(tp))
+		ttydevsw_close(tp);
+
+	tp->t_flags &= ~TF_OPENCLOSE;
+	cv_broadcast(&tp->t_dcdwait);
+	tty_rel_free(tp);
+}
+
+/*
+ * Operations that are exposed through the character device in /dev.
+ */
+static int
+ttydev_open(struct cdev *dev, int oflags, int devtype __unused,
+    struct thread *td)
+{
+	struct tty *tp;
+	int error;
+
+	tp = dev->si_drv1;
+	error = 0;
+	tty_lock(tp);
+	if (tty_gone(tp)) {
+		/* Device is already gone. */
+		tty_unlock(tp);
+		return (ENXIO);
+	}
+
+	/*
+	 * Block when other processes are currently opening or closing
+	 * the TTY.
+	 */
+	while (tp->t_flags & TF_OPENCLOSE) {
+		error = tty_wait(tp, &tp->t_dcdwait);
+		if (error != 0) {
+			tty_unlock(tp);
+			return (error);
+		}
+	}
+	tp->t_flags |= TF_OPENCLOSE;
+
+	/*
+	 * Make sure the "tty" and "cua" device cannot be opened at the
+	 * same time.  The console is a "tty" device.
+	 */
+	if (TTY_CALLOUT(tp, dev)) {
+		if (tp->t_flags & (TF_OPENED_CONS | TF_OPENED_IN)) {
+			error = EBUSY;
+			goto done;
+		}
+	} else {
+		if (tp->t_flags & TF_OPENED_OUT) {
+			error = EBUSY;
+			goto done;
+		}
+	}
+
+	if (tp->t_flags & TF_EXCLUDE && priv_check(td, PRIV_TTY_EXCLUSIVE)) {
+		error = EBUSY;
+		goto done;
+	}
+
+	if (!tty_opened(tp)) {
+		/* Set proper termios flags. */
+		if (TTY_CALLOUT(tp, dev))
+			tp->t_termios = tp->t_termios_init_out;
+		else
+			tp->t_termios = tp->t_termios_init_in;
+		ttydevsw_param(tp, &tp->t_termios);
+		/* Prevent modem control on callout devices and /dev/console. */
+		if (TTY_CALLOUT(tp, dev) || dev == dev_console)
+			tp->t_termios.c_cflag |= CLOCAL;
+
+		ttydevsw_modem(tp, SER_DTR|SER_RTS, 0);
+
+		error = ttydevsw_open(tp);
+		if (error != 0)
+			goto done;
+
+		ttydisc_open(tp);
+		error = tty_watermarks(tp);
+		if (error != 0)
+			goto done;
+	}
+
+	/* Wait for Carrier Detect. */
+	if ((oflags & O_NONBLOCK) == 0 &&
+	    (tp->t_termios.c_cflag & CLOCAL) == 0) {
+		while ((ttydevsw_modem(tp, 0, 0) & SER_DCD) == 0) {
+			error = tty_wait(tp, &tp->t_dcdwait);
+			if (error != 0)
+				goto done;
+		}
+	}
+
+	if (dev == dev_console)
+		tp->t_flags |= TF_OPENED_CONS;
+	else if (TTY_CALLOUT(tp, dev))
+		tp->t_flags |= TF_OPENED_OUT;
+	else
+		tp->t_flags |= TF_OPENED_IN;
+	MPASS((tp->t_flags & (TF_OPENED_CONS | TF_OPENED_IN)) == 0 ||
+	    (tp->t_flags & TF_OPENED_OUT) == 0);
+
+done:	tp->t_flags &= ~TF_OPENCLOSE;
+	cv_broadcast(&tp->t_dcdwait);
+	ttydev_leave(tp);
+
+	return (error);
+}
+
+static int
+ttydev_close(struct cdev *dev, int fflag, int devtype __unused,
+    struct thread *td __unused)
+{
+	struct tty *tp = dev->si_drv1;
+
+	tty_lock(tp);
+
+	/*
+	 * Don't actually close the device if it is being used as the
+	 * console.
+	 */
+	MPASS((tp->t_flags & (TF_OPENED_CONS | TF_OPENED_IN)) == 0 ||
+	    (tp->t_flags & TF_OPENED_OUT) == 0);
+	if (dev == dev_console)
+		tp->t_flags &= ~TF_OPENED_CONS;
+	else
+		tp->t_flags &= ~(TF_OPENED_IN|TF_OPENED_OUT);
+
+	if (tp->t_flags & TF_OPENED) {
+		tty_unlock(tp);
+		return (0);
+	}
+
+	/* If revoking, flush output now to avoid draining it later. */
+	if (fflag & FREVOKE)
+		tty_flush(tp, FWRITE);
+
+	tp->t_flags &= ~TF_EXCLUDE;
+
+	/* Properly wake up threads that are stuck - revoke(). */
+	tp->t_revokecnt++;
+	tty_wakeup(tp, FREAD|FWRITE);
+	cv_broadcast(&tp->t_bgwait);
+	cv_broadcast(&tp->t_dcdwait);
+
+	ttydev_leave(tp);
+
+	return (0);
+}
+
+static __inline int
+tty_is_ctty(struct tty *tp, struct proc *p)
+{
+
+	tty_lock_assert(tp, MA_OWNED);
+
+	return (p->p_session == tp->t_session && p->p_flag & P_CONTROLT);
+}
+
+int
+tty_wait_background(struct tty *tp, struct thread *td, int sig)
+{
+	struct proc *p = td->td_proc;
+	struct pgrp *pg;
+	ksiginfo_t ksi;
+	int error;
+
+	MPASS(sig == SIGTTIN || sig == SIGTTOU);
+	tty_lock_assert(tp, MA_OWNED);
+
+	for (;;) {
+		PROC_LOCK(p);
+		/*
+		 * The process should only sleep, when:
+		 * - This terminal is the controlling terminal
+		 * - Its process group is not the foreground process
+		 *   group
+		 * - The parent process isn't waiting for the child to
+		 *   exit
+		 * - the signal to send to the process isn't masked
+		 */
+		if (!tty_is_ctty(tp, p) || p->p_pgrp == tp->t_pgrp) {
+			/* Allow the action to happen. */
+			PROC_UNLOCK(p);
+			return (0);
+		}
+
+		if (SIGISMEMBER(p->p_sigacts->ps_sigignore, sig) ||
+		    SIGISMEMBER(td->td_sigmask, sig)) {
+			/* Only allow them in write()/ioctl(). */
+			PROC_UNLOCK(p);
+			return (sig == SIGTTOU ? 0 : EIO);
+		}
+
+		pg = p->p_pgrp;
+		if (p->p_flag & P_PPWAIT || pg->pg_jobc == 0) {
+			/* Don't allow the action to happen. */
+			PROC_UNLOCK(p);
+			return (EIO);
+		}
+		PROC_UNLOCK(p);
+
+		/*
+		 * Send the signal and sleep until we're the new
+		 * foreground process group.
+		 */
+		if (sig != 0) {
+			ksiginfo_init(&ksi);
+			ksi.ksi_code = SI_KERNEL;
+			ksi.ksi_signo = sig;
+			sig = 0;
+		}
+		PGRP_LOCK(pg);
+		pgsignal(pg, ksi.ksi_signo, 1, &ksi);
+		PGRP_UNLOCK(pg);
+
+		error = tty_wait(tp, &tp->t_bgwait);
+		if (error)
+			return (error);
+	}
+}
+
+static int
+ttydev_read(struct cdev *dev, struct uio *uio, int ioflag)
+{
+	struct tty *tp = dev->si_drv1;
+	int error;
+
+	error = ttydev_enter(tp);
+	if (error)
+		goto done;
+	error = ttydisc_read(tp, uio, ioflag);
+	tty_unlock(tp);
+
+	/*
+	 * The read() call should not throw an error when the device is
+	 * being destroyed. Silently convert it to an EOF.
+	 */
+done:	if (error == ENXIO)
+		error = 0;
+	return (error);
+}
+
+static int
+ttydev_write(struct cdev *dev, struct uio *uio, int ioflag)
+{
+	struct tty *tp = dev->si_drv1;
+	int error;
+
+	error = ttydev_enter(tp);
+	if (error)
+		return (error);
+
+	if (tp->t_termios.c_lflag & TOSTOP) {
+		error = tty_wait_background(tp, curthread, SIGTTOU);
+		if (error)
+			goto done;
+	}
+
+	if (ioflag & IO_NDELAY && tp->t_flags & TF_BUSY_OUT) {
+		/* Allow non-blocking writes to bypass serialization. */
+		error = ttydisc_write(tp, uio, ioflag);
+	} else {
+		/* Serialize write() calls. */
+		while (tp->t_flags & TF_BUSY_OUT) {
+			error = tty_wait(tp, &tp->t_outserwait);
+			if (error)
+				goto done;
+		}
+
+		tp->t_flags |= TF_BUSY_OUT;
+		error = ttydisc_write(tp, uio, ioflag);
+		tp->t_flags &= ~TF_BUSY_OUT;
+		cv_signal(&tp->t_outserwait);
+	}
+
+done:	tty_unlock(tp);
+	return (error);
+}
+
+static int
+ttydev_ioctl(struct cdev *dev, u_long cmd, caddr_t data, int fflag,
+    struct thread *td)
+{
+	struct tty *tp = dev->si_drv1;
+	int error;
+
+	error = ttydev_enter(tp);
+	if (error)
+		return (error);
+
+	switch (cmd) {
+	case TIOCCBRK:
+	case TIOCCONS:
+	case TIOCDRAIN:
+	case TIOCEXCL:
+	case TIOCFLUSH:
+	case TIOCNXCL:
+	case TIOCSBRK:
+	case TIOCSCTTY:
+	case TIOCSETA:
+	case TIOCSETAF:
+	case TIOCSETAW:
+	case TIOCSPGRP:
+	case TIOCSTART:
+	case TIOCSTAT:
+	case TIOCSTI:
+	case TIOCSTOP:
+	case TIOCSWINSZ:
+#if 0
+	case TIOCSDRAINWAIT:
+	case TIOCSETD:
+#endif
+#ifdef COMPAT_43TTY
+	case  TIOCLBIC:
+	case  TIOCLBIS:
+	case  TIOCLSET:
+	case  TIOCSETC:
+	case OTIOCSETD:
+	case  TIOCSETN:
+	case  TIOCSETP:
+	case  TIOCSLTC:
+#endif /* COMPAT_43TTY */
+		/*
+		 * If the ioctl() causes the TTY to be modified, let it
+		 * wait in the background.
+		 */
+		error = tty_wait_background(tp, curthread, SIGTTOU);
+		if (error)
+			goto done;
+	}
+
+	if (cmd == TIOCSETA || cmd == TIOCSETAW || cmd == TIOCSETAF) {
+		struct termios *old = &tp->t_termios;
+		struct termios *new = (struct termios *)data;
+		struct termios *lock = TTY_CALLOUT(tp, dev) ?
+		    &tp->t_termios_lock_out : &tp->t_termios_lock_in;
+		int cc;
+
+		/*
+		 * Lock state devices.  Just overwrite the values of the
+		 * commands that are currently in use.
+		 */
+		new->c_iflag = (old->c_iflag & lock->c_iflag) |
+		    (new->c_iflag & ~lock->c_iflag);
+		new->c_oflag = (old->c_oflag & lock->c_oflag) |
+		    (new->c_oflag & ~lock->c_oflag);
+		new->c_cflag = (old->c_cflag & lock->c_cflag) |
+		    (new->c_cflag & ~lock->c_cflag);
+		new->c_lflag = (old->c_lflag & lock->c_lflag) |
+		    (new->c_lflag & ~lock->c_lflag);
+		for (cc = 0; cc < NCCS; ++cc)
+			if (lock->c_cc[cc])
+				new->c_cc[cc] = old->c_cc[cc];
+		if (lock->c_ispeed)
+			new->c_ispeed = old->c_ispeed;
+		if (lock->c_ospeed)
+			new->c_ospeed = old->c_ospeed;
+	}
+
+	error = tty_ioctl(tp, cmd, data, fflag, td);
+done:	tty_unlock(tp);
+
+	return (error);
+}
+
+static int
+ttydev_poll(struct cdev *dev, int events, struct thread *td)
+{
+	struct tty *tp = dev->si_drv1;
+	int error, revents = 0;
+
+	error = ttydev_enter(tp);
+	if (error)
+		return ((events & (POLLIN|POLLRDNORM)) | POLLHUP);
+
+	if (events & (POLLIN|POLLRDNORM)) {
+		/* See if we can read something. */
+		if (ttydisc_read_poll(tp) > 0)
+			revents |= events & (POLLIN|POLLRDNORM);
+	}
+
+	if (tp->t_flags & TF_ZOMBIE) {
+		/* Hangup flag on zombie state. */
+		revents |= POLLHUP;
+	} else if (events & (POLLOUT|POLLWRNORM)) {
+		/* See if we can write something. */
+		if (ttydisc_write_poll(tp) > 0)
+			revents |= events & (POLLOUT|POLLWRNORM);
+	}
+
+	if (revents == 0) {
+		if (events & (POLLIN|POLLRDNORM))
+			selrecord(td, &tp->t_inpoll);
+		if (events & (POLLOUT|POLLWRNORM))
+			selrecord(td, &tp->t_outpoll);
+	}
+
+	tty_unlock(tp);
+
+	return (revents);
+}
+
+static int
+ttydev_mmap(struct cdev *dev, vm_ooffset_t offset, vm_paddr_t *paddr,
+    int nprot, vm_memattr_t *memattr)
+{
+	struct tty *tp = dev->si_drv1;
+	int error;
+
+	/* Handle mmap() through the driver. */
+
+	error = ttydev_enter(tp);
+	if (error)
+		return (-1);
+	error = ttydevsw_mmap(tp, offset, paddr, nprot, memattr);
+	tty_unlock(tp);
+
+	return (error);
+}
+
+/*
+ * kqueue support.
+ */
+
+static void
+tty_kqops_read_detach(struct knote *kn)
+{
+	struct tty *tp = kn->kn_hook;
+
+	knlist_remove(&tp->t_inpoll.si_note, kn, 0);
+}
+
+static int
+tty_kqops_read_event(struct knote *kn, long hint __unused)
+{
+	struct tty *tp = kn->kn_hook;
+
+	tty_lock_assert(tp, MA_OWNED);
+
+	if (tty_gone(tp) || tp->t_flags & TF_ZOMBIE) {
+		kn->kn_flags |= EV_EOF;
+		return (1);
+	} else {
+		kn->kn_data = ttydisc_read_poll(tp);
+		return (kn->kn_data > 0);
+	}
+}
+
+static void
+tty_kqops_write_detach(struct knote *kn)
+{
+	struct tty *tp = kn->kn_hook;
+
+	knlist_remove(&tp->t_outpoll.si_note, kn, 0);
+}
+
+static int
+tty_kqops_write_event(struct knote *kn, long hint __unused)
+{
+	struct tty *tp = kn->kn_hook;
+
+	tty_lock_assert(tp, MA_OWNED);
+
+	if (tty_gone(tp)) {
+		kn->kn_flags |= EV_EOF;
+		return (1);
+	} else {
+		kn->kn_data = ttydisc_write_poll(tp);
+		return (kn->kn_data > 0);
+	}
+}
+
+static struct filterops tty_kqops_read = {
+	.f_isfd = 1,
+	.f_detach = tty_kqops_read_detach,
+	.f_event = tty_kqops_read_event,
+};
+
+static struct filterops tty_kqops_write = {
+	.f_isfd = 1,
+	.f_detach = tty_kqops_write_detach,
+	.f_event = tty_kqops_write_event,
+};
+
+static int
+ttydev_kqfilter(struct cdev *dev, struct knote *kn)
+{
+	struct tty *tp = dev->si_drv1;
+	int error;
+
+	error = ttydev_enter(tp);
+	if (error)
+		return (error);
+
+	switch (kn->kn_filter) {
+	case EVFILT_READ:
+		kn->kn_hook = tp;
+		kn->kn_fop = &tty_kqops_read;
+		knlist_add(&tp->t_inpoll.si_note, kn, 1);
+		break;
+	case EVFILT_WRITE:
+		kn->kn_hook = tp;
+		kn->kn_fop = &tty_kqops_write;
+		knlist_add(&tp->t_outpoll.si_note, kn, 1);
+		break;
+	default:
+		error = EINVAL;
+		break;
+	}
+
+	tty_unlock(tp);
+	return (error);
+}
+
+static struct cdevsw ttydev_cdevsw = {
+	.d_version	= D_VERSION,
+	.d_open		= ttydev_open,
+	.d_close	= ttydev_close,
+	.d_read		= ttydev_read,
+	.d_write	= ttydev_write,
+	.d_ioctl	= ttydev_ioctl,
+	.d_kqfilter	= ttydev_kqfilter,
+	.d_poll		= ttydev_poll,
+	.d_mmap		= ttydev_mmap,
+	.d_name		= "ttydev",
+	.d_flags	= D_TTY,
+};
+
+/*
+ * Init/lock-state devices
+ */
+
+static int
+ttyil_open(struct cdev *dev, int oflags __unused, int devtype __unused,
+    struct thread *td)
+{
+	struct tty *tp;
+	int error;
+
+	tp = dev->si_drv1;
+	error = 0;
+	tty_lock(tp);
+	if (tty_gone(tp))
+		error = ENODEV;
+	tty_unlock(tp);
+
+	return (error);
+}
+
+static int
+ttyil_close(struct cdev *dev __unused, int flag __unused, int mode __unused,
+    struct thread *td __unused)
+{
+
+	return (0);
+}
+
+static int
+ttyil_rdwr(struct cdev *dev __unused, struct uio *uio __unused,
+    int ioflag __unused)
+{
+
+	return (ENODEV);
+}
+
+static int
+ttyil_ioctl(struct cdev *dev, u_long cmd, caddr_t data, int fflag,
+    struct thread *td)
+{
+	struct tty *tp = dev->si_drv1;
+	int error;
+
+	tty_lock(tp);
+	if (tty_gone(tp)) {
+		error = ENODEV;
+		goto done;
+	}
+
+	error = ttydevsw_cioctl(tp, dev2unit(dev), cmd, data, td);
+	if (error != ENOIOCTL)
+		goto done;
+	error = 0;
+
+	switch (cmd) {
+	case TIOCGETA:
+		/* Obtain terminal flags through tcgetattr(). */
+		*(struct termios*)data = *(struct termios*)dev->si_drv2;
+		break;
+	case TIOCSETA:
+		/* Set terminal flags through tcsetattr(). */
+		error = priv_check(td, PRIV_TTY_SETA);
+		if (error)
+			break;
+		*(struct termios*)dev->si_drv2 = *(struct termios*)data;
+		break;
+	case TIOCGETD:
+		*(int *)data = TTYDISC;
+		break;
+	case TIOCGWINSZ:
+		bzero(data, sizeof(struct winsize));
+		break;
+	default:
+		error = ENOTTY;
+	}
+
+done:	tty_unlock(tp);
+	return (error);
+}
+
+static struct cdevsw ttyil_cdevsw = {
+	.d_version	= D_VERSION,
+	.d_open		= ttyil_open,
+	.d_close	= ttyil_close,
+	.d_read		= ttyil_rdwr,
+	.d_write	= ttyil_rdwr,
+	.d_ioctl	= ttyil_ioctl,
+	.d_name		= "ttyil",
+	.d_flags	= D_TTY,
+};
+
+static void
+tty_init_termios(struct tty *tp)
+{
+	struct termios *t = &tp->t_termios_init_in;
+
+	t->c_cflag = TTYDEF_CFLAG;
+	t->c_iflag = TTYDEF_IFLAG;
+	t->c_lflag = TTYDEF_LFLAG;
+	t->c_oflag = TTYDEF_OFLAG;
+	t->c_ispeed = TTYDEF_SPEED;
+	t->c_ospeed = TTYDEF_SPEED;
+	memcpy(&t->c_cc, ttydefchars, sizeof ttydefchars);
+
+	tp->t_termios_init_out = *t;
+}
+
+void
+tty_init_console(struct tty *tp, speed_t s)
+{
+	struct termios *ti = &tp->t_termios_init_in;
+	struct termios *to = &tp->t_termios_init_out;
+
+	if (s != 0) {
+		ti->c_ispeed = ti->c_ospeed = s;
+		to->c_ispeed = to->c_ospeed = s;
+	}
+
+	ti->c_cflag |= CLOCAL;
+	to->c_cflag |= CLOCAL;
+}
+
+/*
+ * Standard device routine implementations, mostly meant for
+ * pseudo-terminal device drivers. When a driver creates a new terminal
+ * device class, missing routines are patched.
+ */
+
+static int
+ttydevsw_defopen(struct tty *tp __unused)
+{
+
+	return (0);
+}
+
+static void
+ttydevsw_defclose(struct tty *tp __unused)
+{
+
+}
+
+static void
+ttydevsw_defoutwakeup(struct tty *tp __unused)
+{
+
+	panic("Terminal device has output, while not implemented");
+}
+
+static void
+ttydevsw_definwakeup(struct tty *tp __unused)
+{
+
+}
+
+static int
+ttydevsw_defioctl(struct tty *tp __unused, u_long cmd __unused,
+    caddr_t data __unused, struct thread *td __unused)
+{
+
+	return (ENOIOCTL);
+}
+
+static int
+ttydevsw_defcioctl(struct tty *tp __unused, int unit __unused,
+    u_long cmd __unused, caddr_t data __unused, struct thread *td __unused)
+{
+
+	return (ENOIOCTL);
+}
+
+static int
+ttydevsw_defparam(struct tty *tp __unused, struct termios *t)
+{
+
+	/*
+	 * Allow the baud rate to be adjusted for pseudo-devices, but at
+	 * least restrict it to 115200 to prevent excessive buffer
+	 * usage.  Also disallow 0, to prevent foot shooting.
+	 */
+	if (t->c_ispeed < B50)
+		t->c_ispeed = B50;
+	else if (t->c_ispeed > B115200)
+		t->c_ispeed = B115200;
+	if (t->c_ospeed < B50)
+		t->c_ospeed = B50;
+	else if (t->c_ospeed > B115200)
+		t->c_ospeed = B115200;
+	t->c_cflag |= CREAD;
+
+	return (0);
+}
+
+static int
+ttydevsw_defmodem(struct tty *tp __unused, int sigon __unused,
+    int sigoff __unused)
+{
+
+	/* Simulate a carrier to make the TTY layer happy. */
+	return (SER_DCD);
+}
+
+static int
+ttydevsw_defmmap(struct tty *tp __unused, vm_ooffset_t offset __unused,
+    vm_paddr_t *paddr __unused, int nprot __unused,
+    vm_memattr_t *memattr __unused)
+{
+
+	return (-1);
+}
+
+static void
+ttydevsw_defpktnotify(struct tty *tp __unused, char event __unused)
+{
+
+}
+
+static void
+ttydevsw_deffree(void *softc __unused)
+{
+
+	panic("Terminal device freed without a free-handler");
+}
+
+static bool
+ttydevsw_defbusy(struct tty *tp __unused)
+{
+
+	return (FALSE);
+}
+
+/*
+ * TTY allocation and deallocation. TTY devices can be deallocated when
+ * the driver doesn't use it anymore, when the TTY isn't a session's
+ * controlling TTY and when the device node isn't opened through devfs.
+ */
+
+struct tty *
+tty_alloc(struct ttydevsw *tsw, void *sc)
+{
+
+	return (tty_alloc_mutex(tsw, sc, NULL));
+}
+
+struct tty *
+tty_alloc_mutex(struct ttydevsw *tsw, void *sc, struct mtx *mutex)
+{
+	struct tty *tp;
+
+	/* Make sure the driver defines all routines. */
+#define PATCH_FUNC(x) do {				\
+	if (tsw->tsw_ ## x == NULL)			\
+		tsw->tsw_ ## x = ttydevsw_def ## x;	\
+} while (0)
+	PATCH_FUNC(open);
+	PATCH_FUNC(close);
+	PATCH_FUNC(outwakeup);
+	PATCH_FUNC(inwakeup);
+	PATCH_FUNC(ioctl);
+	PATCH_FUNC(cioctl);
+	PATCH_FUNC(param);
+	PATCH_FUNC(modem);
+	PATCH_FUNC(mmap);
+	PATCH_FUNC(pktnotify);
+	PATCH_FUNC(free);
+	PATCH_FUNC(busy);
+#undef PATCH_FUNC
+
+	tp = malloc(sizeof(struct tty), M_TTY, M_WAITOK|M_ZERO);
+	tp->t_devsw = tsw;
+	tp->t_devswsoftc = sc;
+	tp->t_flags = tsw->tsw_flags;
+	tp->t_drainwait = tty_drainwait;
+
+	tty_init_termios(tp);
+
+	cv_init(&tp->t_inwait, "ttyin");
+	cv_init(&tp->t_outwait, "ttyout");
+	cv_init(&tp->t_outserwait, "ttyosr");
+	cv_init(&tp->t_bgwait, "ttybg");
+	cv_init(&tp->t_dcdwait, "ttydcd");
+
+	/* Allow drivers to use a custom mutex to lock the TTY. */
+	if (mutex != NULL) {
+		tp->t_mtx = mutex;
+	} else {
+		tp->t_mtx = &tp->t_mtxobj;
+		mtx_init(&tp->t_mtxobj, "ttymtx", NULL, MTX_DEF);
+	}
+
+	knlist_init_mtx(&tp->t_inpoll.si_note, tp->t_mtx);
+	knlist_init_mtx(&tp->t_outpoll.si_note, tp->t_mtx);
+
+	return (tp);
+}
+
+static void
+tty_dealloc(void *arg)
+{
+	struct tty *tp = arg;
+
+	/*
+	 * ttyydev_leave() usually frees the i/o queues earlier, but it is
+	 * not always called between queue allocation and here.  The queues
+	 * may be allocated by ioctls on a pty control device without the
+	 * corresponding pty slave device ever being open, or after it is
+	 * closed.
+	 */
+	ttyinq_free(&tp->t_inq);
+	ttyoutq_free(&tp->t_outq);
+	seldrain(&tp->t_inpoll);
+	seldrain(&tp->t_outpoll);
+	knlist_destroy(&tp->t_inpoll.si_note);
+	knlist_destroy(&tp->t_outpoll.si_note);
+
+	cv_destroy(&tp->t_inwait);
+	cv_destroy(&tp->t_outwait);
+	cv_destroy(&tp->t_bgwait);
+	cv_destroy(&tp->t_dcdwait);
+	cv_destroy(&tp->t_outserwait);
+
+	if (tp->t_mtx == &tp->t_mtxobj)
+		mtx_destroy(&tp->t_mtxobj);
+	ttydevsw_free(tp);
+	free(tp, M_TTY);
+}
+
+static void
+tty_rel_free(struct tty *tp)
+{
+	struct cdev *dev;
+
+	tty_lock_assert(tp, MA_OWNED);
+
+#define	TF_ACTIVITY	(TF_GONE|TF_OPENED|TF_HOOK|TF_OPENCLOSE)
+	if (tp->t_sessioncnt != 0 || (tp->t_flags & TF_ACTIVITY) != TF_GONE) {
+		/* TTY is still in use. */
+		tty_unlock(tp);
+		return;
+	}
+
+	/* TTY can be deallocated. */
+	dev = tp->t_dev;
+	tp->t_dev = NULL;
+	tty_unlock(tp);
+
+	if (dev != NULL) {
+		sx_xlock(&tty_list_sx);
+		TAILQ_REMOVE(&tty_list, tp, t_list);
+		tty_list_count--;
+		sx_xunlock(&tty_list_sx);
+		destroy_dev_sched_cb(dev, tty_dealloc, tp);
+	}
+}
+
+void
+tty_rel_pgrp(struct tty *tp, struct pgrp *pg)
+{
+
+	MPASS(tp->t_sessioncnt > 0);
+	tty_lock_assert(tp, MA_OWNED);
+
+	if (tp->t_pgrp == pg)
+		tp->t_pgrp = NULL;
+
+	tty_unlock(tp);
+}
+
+void
+tty_rel_sess(struct tty *tp, struct session *sess)
+{
+
+	MPASS(tp->t_sessioncnt > 0);
+
+	/* Current session has left. */
+	if (tp->t_session == sess) {
+		tp->t_session = NULL;
+		MPASS(tp->t_pgrp == NULL);
+	}
+	tp->t_sessioncnt--;
+	tty_rel_free(tp);
+}
+
+void
+tty_rel_gone(struct tty *tp)
+{
+
+	MPASS(!tty_gone(tp));
+
+	/* Simulate carrier removal. */
+	ttydisc_modem(tp, 0);
+
+	/* Wake up all blocked threads. */
+	tty_wakeup(tp, FREAD|FWRITE);
+	cv_broadcast(&tp->t_bgwait);
+	cv_broadcast(&tp->t_dcdwait);
+
+	tp->t_flags |= TF_GONE;
+	tty_rel_free(tp);
+}
+
+/*
+ * Exposing information about current TTY's through sysctl
+ */
+
+static void
+tty_to_xtty(struct tty *tp, struct xtty *xt)
+{
+
+	tty_lock_assert(tp, MA_OWNED);
+
+	xt->xt_size = sizeof(struct xtty);
+	xt->xt_insize = ttyinq_getsize(&tp->t_inq);
+	xt->xt_incc = ttyinq_bytescanonicalized(&tp->t_inq);
+	xt->xt_inlc = ttyinq_bytesline(&tp->t_inq);
+	xt->xt_inlow = tp->t_inlow;
+	xt->xt_outsize = ttyoutq_getsize(&tp->t_outq);
+	xt->xt_outcc = ttyoutq_bytesused(&tp->t_outq);
+	xt->xt_outlow = tp->t_outlow;
+	xt->xt_column = tp->t_column;
+	xt->xt_pgid = tp->t_pgrp ? tp->t_pgrp->pg_id : 0;
+	xt->xt_sid = tp->t_session ? tp->t_session->s_sid : 0;
+	xt->xt_flags = tp->t_flags;
+	xt->xt_dev = tp->t_dev ? dev2udev(tp->t_dev) : NODEV;
+}
+
+static int
+sysctl_kern_ttys(SYSCTL_HANDLER_ARGS)
+{
+	unsigned long lsize;
+	struct xtty *xtlist, *xt;
+	struct tty *tp;
+	int error;
+
+	sx_slock(&tty_list_sx);
+	lsize = tty_list_count * sizeof(struct xtty);
+	if (lsize == 0) {
+		sx_sunlock(&tty_list_sx);
+		return (0);
+	}
+
+	xtlist = xt = malloc(lsize, M_TTY, M_WAITOK);
+
+	TAILQ_FOREACH(tp, &tty_list, t_list) {
+		tty_lock(tp);
+		tty_to_xtty(tp, xt);
+		tty_unlock(tp);
+		xt++;
+	}
+	sx_sunlock(&tty_list_sx);
+
+	error = SYSCTL_OUT(req, xtlist, lsize);
+	free(xtlist, M_TTY);
+	return (error);
+}
+
+SYSCTL_PROC(_kern, OID_AUTO, ttys, CTLTYPE_OPAQUE|CTLFLAG_RD|CTLFLAG_MPSAFE,
+	0, 0, sysctl_kern_ttys, "S,xtty", "List of TTYs");
+
+/*
+ * Device node creation. Device has been set up, now we can expose it to
+ * the user.
+ */
+
+int
+tty_makedevf(struct tty *tp, struct ucred *cred, int flags,
+    const char *fmt, ...)
+{
+	va_list ap;
+	struct make_dev_args args;
+	struct cdev *dev, *init, *lock, *cua, *cinit, *clock;
+	const char *prefix = "tty";
+	char name[SPECNAMELEN - 3]; /* for "tty" and "cua". */
+	uid_t uid;
+	gid_t gid;
+	mode_t mode;
+	int error;
+
+	/* Remove "tty" prefix from devices like PTY's. */
+	if (tp->t_flags & TF_NOPREFIX)
+		prefix = "";
+
+	va_start(ap, fmt);
+	vsnrprintf(name, sizeof name, 32, fmt, ap);
+	va_end(ap);
+
+	if (cred == NULL) {
+		/* System device. */
+		uid = UID_ROOT;
+		gid = GID_WHEEL;
+		mode = S_IRUSR|S_IWUSR;
+	} else {
+		/* User device. */
+		uid = cred->cr_ruid;
+		gid = GID_TTY;
+		mode = S_IRUSR|S_IWUSR|S_IWGRP;
+	}
+
+	flags = flags & TTYMK_CLONING ? MAKEDEV_REF : 0;
+	flags |= MAKEDEV_CHECKNAME;
+
+	/* Master call-in device. */
+	make_dev_args_init(&args);
+	args.mda_flags = flags;
+	args.mda_devsw = &ttydev_cdevsw;
+	args.mda_cr = cred;
+	args.mda_uid = uid;
+	args.mda_gid = gid;
+	args.mda_mode = mode;
+	args.mda_si_drv1 = tp;
+	error = make_dev_s(&args, &dev, "%s%s", prefix, name);
+	if (error != 0)
+		return (error);
+	tp->t_dev = dev;
+
+	init = lock = cua = cinit = clock = NULL;
+
+	/* Slave call-in devices. */
+	if (tp->t_flags & TF_INITLOCK) {
+		args.mda_devsw = &ttyil_cdevsw;
+		args.mda_unit = TTYUNIT_INIT;
+		args.mda_si_drv1 = tp;
+		args.mda_si_drv2 = &tp->t_termios_init_in;
+		error = make_dev_s(&args, &init, "%s%s.init", prefix, name);
+		if (error != 0)
+			goto fail;
+		dev_depends(dev, init);
+
+		args.mda_unit = TTYUNIT_LOCK;
+		args.mda_si_drv2 = &tp->t_termios_lock_in;
+		error = make_dev_s(&args, &lock, "%s%s.lock", prefix, name);
+		if (error != 0)
+			goto fail;
+		dev_depends(dev, lock);
+	}
+
+	/* Call-out devices. */
+	if (tp->t_flags & TF_CALLOUT) {
+		make_dev_args_init(&args);
+		args.mda_flags = flags;
+		args.mda_devsw = &ttydev_cdevsw;
+		args.mda_cr = cred;
+		args.mda_uid = UID_UUCP;
+		args.mda_gid = GID_DIALER;
+		args.mda_mode = 0660;
+		args.mda_unit = TTYUNIT_CALLOUT;
+		args.mda_si_drv1 = tp;
+		error = make_dev_s(&args, &cua, "cua%s", name);
+		if (error != 0)
+			goto fail;
+		dev_depends(dev, cua);
+
+		/* Slave call-out devices. */
+		if (tp->t_flags & TF_INITLOCK) {
+			args.mda_devsw = &ttyil_cdevsw;
+			args.mda_unit = TTYUNIT_CALLOUT | TTYUNIT_INIT;
+			args.mda_si_drv2 = &tp->t_termios_init_out;
+			error = make_dev_s(&args, &cinit, "cua%s.init", name);
+			if (error != 0)
+				goto fail;
+			dev_depends(dev, cinit);
+
+			args.mda_unit = TTYUNIT_CALLOUT | TTYUNIT_LOCK;
+			args.mda_si_drv2 = &tp->t_termios_lock_out;
+			error = make_dev_s(&args, &clock, "cua%s.lock", name);
+			if (error != 0)
+				goto fail;
+			dev_depends(dev, clock);
+		}
+	}
+
+	sx_xlock(&tty_list_sx);
+	TAILQ_INSERT_TAIL(&tty_list, tp, t_list);
+	tty_list_count++;
+	sx_xunlock(&tty_list_sx);
+
+	return (0);
+
+fail:
+	destroy_dev(dev);
+	if (init)
+		destroy_dev(init);
+	if (lock)
+		destroy_dev(lock);
+	if (cinit)
+		destroy_dev(cinit);
+	if (clock)
+		destroy_dev(clock);
+
+	return (error);
+}
+
+/*
+ * Signalling processes.
+ */
+
+void
+tty_signal_sessleader(struct tty *tp, int sig)
+{
+	struct proc *p;
+
+	tty_lock_assert(tp, MA_OWNED);
+	MPASS(sig >= 1 && sig < NSIG);
+
+	/* Make signals start output again. */
+	tp->t_flags &= ~TF_STOPPED;
+
+	if (tp->t_session != NULL && tp->t_session->s_leader != NULL) {
+		p = tp->t_session->s_leader;
+		PROC_LOCK(p);
+		kern_psignal(p, sig);
+		PROC_UNLOCK(p);
+	}
+}
+
+void
+tty_signal_pgrp(struct tty *tp, int sig)
+{
+	ksiginfo_t ksi;
+
+	tty_lock_assert(tp, MA_OWNED);
+	MPASS(sig >= 1 && sig < NSIG);
+
+	/* Make signals start output again. */
+	tp->t_flags &= ~TF_STOPPED;
+
+	if (sig == SIGINFO && !(tp->t_termios.c_lflag & NOKERNINFO))
+		tty_info(tp);
+	if (tp->t_pgrp != NULL) {
+		ksiginfo_init(&ksi);
+		ksi.ksi_signo = sig;
+		ksi.ksi_code = SI_KERNEL;
+		PGRP_LOCK(tp->t_pgrp);
+		pgsignal(tp->t_pgrp, sig, 1, &ksi);
+		PGRP_UNLOCK(tp->t_pgrp);
+	}
+}
+
+void
+tty_wakeup(struct tty *tp, int flags)
+{
+
+	if (tp->t_flags & TF_ASYNC && tp->t_sigio != NULL)
+		pgsigio(&tp->t_sigio, SIGIO, (tp->t_session != NULL));
+
+	if (flags & FWRITE) {
+		cv_broadcast(&tp->t_outwait);
+		selwakeup(&tp->t_outpoll);
+		KNOTE_LOCKED(&tp->t_outpoll.si_note, 0);
+	}
+	if (flags & FREAD) {
+		cv_broadcast(&tp->t_inwait);
+		selwakeup(&tp->t_inpoll);
+		KNOTE_LOCKED(&tp->t_inpoll.si_note, 0);
+	}
+}
+
+int
+tty_wait(struct tty *tp, struct cv *cv)
+{
+	int error;
+	int revokecnt = tp->t_revokecnt;
+
+	tty_lock_assert(tp, MA_OWNED|MA_NOTRECURSED);
+	MPASS(!tty_gone(tp));
+
+	error = cv_wait_sig(cv, tp->t_mtx);
+
+	/* Bail out when the device slipped away. */
+	if (tty_gone(tp))
+		return (ENXIO);
+
+	/* Restart the system call when we may have been revoked. */
+	if (tp->t_revokecnt != revokecnt)
+		return (ERESTART);
+
+	return (error);
+}
+
+int
+tty_timedwait(struct tty *tp, struct cv *cv, int hz)
+{
+	int error;
+	int revokecnt = tp->t_revokecnt;
+
+	tty_lock_assert(tp, MA_OWNED|MA_NOTRECURSED);
+	MPASS(!tty_gone(tp));
+
+	error = cv_timedwait_sig(cv, tp->t_mtx, hz);
+
+	/* Bail out when the device slipped away. */
+	if (tty_gone(tp))
+		return (ENXIO);
+
+	/* Restart the system call when we may have been revoked. */
+	if (tp->t_revokecnt != revokecnt)
+		return (ERESTART);
+
+	return (error);
+}
+
+void
+tty_flush(struct tty *tp, int flags)
+{
+
+	if (flags & FWRITE) {
+		tp->t_flags &= ~TF_HIWAT_OUT;
+		ttyoutq_flush(&tp->t_outq);
+		tty_wakeup(tp, FWRITE);
+		if (!tty_gone(tp)) {
+			ttydevsw_outwakeup(tp);
+			ttydevsw_pktnotify(tp, TIOCPKT_FLUSHWRITE);
+		}
+	}
+	if (flags & FREAD) {
+		tty_hiwat_in_unblock(tp);
+		ttyinq_flush(&tp->t_inq);
+		tty_wakeup(tp, FREAD);
+		if (!tty_gone(tp)) {
+			ttydevsw_inwakeup(tp);
+			ttydevsw_pktnotify(tp, TIOCPKT_FLUSHREAD);
+		}
+	}
+}
+
+void
+tty_set_winsize(struct tty *tp, const struct winsize *wsz)
+{
+
+	if (memcmp(&tp->t_winsize, wsz, sizeof(*wsz)) == 0)
+		return;
+	tp->t_winsize = *wsz;
+	tty_signal_pgrp(tp, SIGWINCH);
+}
+
+static int
+tty_generic_ioctl(struct tty *tp, u_long cmd, void *data, int fflag,
+    struct thread *td)
+{
+	int error;
+
+	switch (cmd) {
+	/*
+	 * Modem commands.
+	 * The SER_* and TIOCM_* flags are the same, but one bit
+	 * shifted. I don't know why.
+	 */
+	case TIOCSDTR:
+		ttydevsw_modem(tp, SER_DTR, 0);
+		return (0);
+	case TIOCCDTR:
+		ttydevsw_modem(tp, 0, SER_DTR);
+		return (0);
+	case TIOCMSET: {
+		int bits = *(int *)data;
+		ttydevsw_modem(tp,
+		    (bits & (TIOCM_DTR | TIOCM_RTS)) >> 1,
+		    ((~bits) & (TIOCM_DTR | TIOCM_RTS)) >> 1);
+		return (0);
+	}
+	case TIOCMBIS: {
+		int bits = *(int *)data;
+		ttydevsw_modem(tp, (bits & (TIOCM_DTR | TIOCM_RTS)) >> 1, 0);
+		return (0);
+	}
+	case TIOCMBIC: {
+		int bits = *(int *)data;
+		ttydevsw_modem(tp, 0, (bits & (TIOCM_DTR | TIOCM_RTS)) >> 1);
+		return (0);
+	}
+	case TIOCMGET:
+		*(int *)data = TIOCM_LE + (ttydevsw_modem(tp, 0, 0) << 1);
+		return (0);
+
+	case FIOASYNC:
+		if (*(int *)data)
+			tp->t_flags |= TF_ASYNC;
+		else
+			tp->t_flags &= ~TF_ASYNC;
+		return (0);
+	case FIONBIO:
+		/* This device supports non-blocking operation. */
+		return (0);
+	case FIONREAD:
+		*(int *)data = ttyinq_bytescanonicalized(&tp->t_inq);
+		return (0);
+	case FIONWRITE:
+	case TIOCOUTQ:
+		*(int *)data = ttyoutq_bytesused(&tp->t_outq);
+		return (0);
+	case FIOSETOWN:
+		if (tp->t_session != NULL && !tty_is_ctty(tp, td->td_proc))
+			/* Not allowed to set ownership. */
+			return (ENOTTY);
+
+		/* Temporarily unlock the TTY to set ownership. */
+		tty_unlock(tp);
+		error = fsetown(*(int *)data, &tp->t_sigio);
+		tty_lock(tp);
+		return (error);
+	case FIOGETOWN:
+		if (tp->t_session != NULL && !tty_is_ctty(tp, td->td_proc))
+			/* Not allowed to set ownership. */
+			return (ENOTTY);
+
+		/* Get ownership. */
+		*(int *)data = fgetown(&tp->t_sigio);
+		return (0);
+	case TIOCGETA:
+		/* Obtain terminal flags through tcgetattr(). */
+		*(struct termios*)data = tp->t_termios;
+		return (0);
+	case TIOCSETA:
+	case TIOCSETAW:
+	case TIOCSETAF: {
+		struct termios *t = data;
+
+		/*
+		 * Who makes up these funny rules? According to POSIX,
+		 * input baud rate is set equal to the output baud rate
+		 * when zero.
+		 */
+		if (t->c_ispeed == 0)
+			t->c_ispeed = t->c_ospeed;
+
+		/* Discard any unsupported bits. */
+		t->c_iflag &= TTYSUP_IFLAG;
+		t->c_oflag &= TTYSUP_OFLAG;
+		t->c_lflag &= TTYSUP_LFLAG;
+		t->c_cflag &= TTYSUP_CFLAG;
+
+		/* Set terminal flags through tcsetattr(). */
+		if (cmd == TIOCSETAW || cmd == TIOCSETAF) {
+			error = tty_drain(tp, 0);
+			if (error)
+				return (error);
+			if (cmd == TIOCSETAF)
+				tty_flush(tp, FREAD);
+		}
+
+		/*
+		 * Only call param() when the flags really change.
+		 */
+		if ((t->c_cflag & CIGNORE) == 0 &&
+		    (tp->t_termios.c_cflag != t->c_cflag ||
+		    ((tp->t_termios.c_iflag ^ t->c_iflag) &
+		    (IXON|IXOFF|IXANY)) ||
+		    tp->t_termios.c_ispeed != t->c_ispeed ||
+		    tp->t_termios.c_ospeed != t->c_ospeed)) {
+			error = ttydevsw_param(tp, t);
+			if (error)
+				return (error);
+
+			/* XXX: CLOCAL? */
+
+			tp->t_termios.c_cflag = t->c_cflag & ~CIGNORE;
+			tp->t_termios.c_ispeed = t->c_ispeed;
+			tp->t_termios.c_ospeed = t->c_ospeed;
+
+			/* Baud rate has changed - update watermarks. */
+			error = tty_watermarks(tp);
+			if (error)
+				return (error);
+		}
+
+		/* Copy new non-device driver parameters. */
+		tp->t_termios.c_iflag = t->c_iflag;
+		tp->t_termios.c_oflag = t->c_oflag;
+		tp->t_termios.c_lflag = t->c_lflag;
+		memcpy(&tp->t_termios.c_cc, t->c_cc, sizeof t->c_cc);
+
+		ttydisc_optimize(tp);
+
+		if ((t->c_lflag & ICANON) == 0) {
+			/*
+			 * When in non-canonical mode, wake up all
+			 * readers. Canonicalize any partial input. VMIN
+			 * and VTIME could also be adjusted.
+			 */
+			ttyinq_canonicalize(&tp->t_inq);
+			tty_wakeup(tp, FREAD);
+		}
+
+		/*
+		 * For packet mode: notify the PTY consumer that VSTOP
+		 * and VSTART may have been changed.
+		 */
+		if (tp->t_termios.c_iflag & IXON &&
+		    tp->t_termios.c_cc[VSTOP] == CTRL('S') &&
+		    tp->t_termios.c_cc[VSTART] == CTRL('Q'))
+			ttydevsw_pktnotify(tp, TIOCPKT_DOSTOP);
+		else
+			ttydevsw_pktnotify(tp, TIOCPKT_NOSTOP);
+		return (0);
+	}
+	case TIOCGETD:
+		/* For compatibility - we only support TTYDISC. */
+		*(int *)data = TTYDISC;
+		return (0);
+	case TIOCGPGRP:
+		if (!tty_is_ctty(tp, td->td_proc))
+			return (ENOTTY);
+
+		if (tp->t_pgrp != NULL)
+			*(int *)data = tp->t_pgrp->pg_id;
+		else
+			*(int *)data = NO_PID;
+		return (0);
+	case TIOCGSID:
+		if (!tty_is_ctty(tp, td->td_proc))
+			return (ENOTTY);
+
+		MPASS(tp->t_session);
+		*(int *)data = tp->t_session->s_sid;
+		return (0);
+	case TIOCSCTTY: {
+		struct proc *p = td->td_proc;
+
+		/* XXX: This looks awful. */
+		tty_unlock(tp);
+		sx_xlock(&proctree_lock);
+		tty_lock(tp);
+
+		if (!SESS_LEADER(p)) {
+			/* Only the session leader may do this. */
+			sx_xunlock(&proctree_lock);
+			return (EPERM);
+		}
+
+		if (tp->t_session != NULL && tp->t_session == p->p_session) {
+			/* This is already our controlling TTY. */
+			sx_xunlock(&proctree_lock);
+			return (0);
+		}
+
+		if (p->p_session->s_ttyp != NULL ||
+		    (tp->t_session != NULL && tp->t_session->s_ttyvp != NULL &&
+		    tp->t_session->s_ttyvp->v_type != VBAD)) {
+			/*
+			 * There is already a relation between a TTY and
+			 * a session, or the caller is not the session
+			 * leader.
+			 *
+			 * Allow the TTY to be stolen when the vnode is
+			 * invalid, but the reference to the TTY is
+			 * still active.  This allows immediate reuse of
+			 * TTYs of which the session leader has been
+			 * killed or the TTY revoked.
+			 */
+			sx_xunlock(&proctree_lock);
+			return (EPERM);
+		}
+
+		/* Connect the session to the TTY. */
+		tp->t_session = p->p_session;
+		tp->t_session->s_ttyp = tp;
+		tp->t_sessioncnt++;
+		sx_xunlock(&proctree_lock);
+
+		/* Assign foreground process group. */
+		tp->t_pgrp = p->p_pgrp;
+		PROC_LOCK(p);
+		p->p_flag |= P_CONTROLT;
+		PROC_UNLOCK(p);
+
+		return (0);
+	}
+	case TIOCSPGRP: {
+		struct pgrp *pg;
+
+		/*
+		 * XXX: Temporarily unlock the TTY to locate the process
+		 * group. This code would be lot nicer if we would ever
+		 * decompose proctree_lock.
+		 */
+		tty_unlock(tp);
+		sx_slock(&proctree_lock);
+		pg = pgfind(*(int *)data);
+		if (pg != NULL)
+			PGRP_UNLOCK(pg);
+		if (pg == NULL || pg->pg_session != td->td_proc->p_session) {
+			sx_sunlock(&proctree_lock);
+			tty_lock(tp);
+			return (EPERM);
+		}
+		tty_lock(tp);
+
+		/*
+		 * Determine if this TTY is the controlling TTY after
+		 * relocking the TTY.
+		 */
+		if (!tty_is_ctty(tp, td->td_proc)) {
+			sx_sunlock(&proctree_lock);
+			return (ENOTTY);
+		}
+		tp->t_pgrp = pg;
+		sx_sunlock(&proctree_lock);
+
+		/* Wake up the background process groups. */
+		cv_broadcast(&tp->t_bgwait);
+		return (0);
+	}
+	case TIOCFLUSH: {
+		int flags = *(int *)data;
+
+		if (flags == 0)
+			flags = (FREAD|FWRITE);
+		else
+			flags &= (FREAD|FWRITE);
+		tty_flush(tp, flags);
+		return (0);
+	}
+	case TIOCDRAIN:
+		/* Drain TTY output. */
+		return tty_drain(tp, 0);
+	case TIOCGDRAINWAIT:
+		*(int *)data = tp->t_drainwait;
+		return (0);
+	case TIOCSDRAINWAIT:
+		error = priv_check(td, PRIV_TTY_DRAINWAIT);
+		if (error == 0)
+			tp->t_drainwait = *(int *)data;
+		return (error);
+	case TIOCCONS:
+		/* Set terminal as console TTY. */
+		if (*(int *)data) {
+			error = priv_check(td, PRIV_TTY_CONSOLE);
+			if (error)
+				return (error);
+
+			/*
+			 * XXX: constty should really need to be locked!
+			 * XXX: allow disconnected constty's to be stolen!
+			 */
+
+			if (constty == tp)
+				return (0);
+			if (constty != NULL)
+				return (EBUSY);
+
+			tty_unlock(tp);
+			constty_set(tp);
+			tty_lock(tp);
+		} else if (constty == tp) {
+			constty_clear();
+		}
+		return (0);
+	case TIOCGWINSZ:
+		/* Obtain window size. */
+		*(struct winsize*)data = tp->t_winsize;
+		return (0);
+	case TIOCSWINSZ:
+		/* Set window size. */
+		tty_set_winsize(tp, data);
+		return (0);
+	case TIOCEXCL:
+		tp->t_flags |= TF_EXCLUDE;
+		return (0);
+	case TIOCNXCL:
+		tp->t_flags &= ~TF_EXCLUDE;
+		return (0);
+	case TIOCSTOP:
+		tp->t_flags |= TF_STOPPED;
+		ttydevsw_pktnotify(tp, TIOCPKT_STOP);
+		return (0);
+	case TIOCSTART:
+		tp->t_flags &= ~TF_STOPPED;
+		ttydevsw_outwakeup(tp);
+		ttydevsw_pktnotify(tp, TIOCPKT_START);
+		return (0);
+	case TIOCSTAT:
+		tty_info(tp);
+		return (0);
+	case TIOCSTI:
+		if ((fflag & FREAD) == 0 && priv_check(td, PRIV_TTY_STI))
+			return (EPERM);
+		if (!tty_is_ctty(tp, td->td_proc) &&
+		    priv_check(td, PRIV_TTY_STI))
+			return (EACCES);
+		ttydisc_rint(tp, *(char *)data, 0);
+		ttydisc_rint_done(tp);
+		return (0);
+	}
+
+#ifdef COMPAT_43TTY
+	return tty_ioctl_compat(tp, cmd, data, fflag, td);
+#else /* !COMPAT_43TTY */
+	return (ENOIOCTL);
+#endif /* COMPAT_43TTY */
+}
+
+int
+tty_ioctl(struct tty *tp, u_long cmd, void *data, int fflag, struct thread *td)
+{
+	int error;
+
+	tty_lock_assert(tp, MA_OWNED);
+
+	if (tty_gone(tp))
+		return (ENXIO);
+
+	error = ttydevsw_ioctl(tp, cmd, data, td);
+	if (error == ENOIOCTL)
+		error = tty_generic_ioctl(tp, cmd, data, fflag, td);
+
+	return (error);
+}
+
+dev_t
+tty_udev(struct tty *tp)
+{
+
+	if (tp->t_dev)
+		return (dev2udev(tp->t_dev));
+	else
+		return (NODEV);
+}
+
+int
+tty_checkoutq(struct tty *tp)
+{
+
+	/* 256 bytes should be enough to print a log message. */
+	return (ttyoutq_bytesleft(&tp->t_outq) >= 256);
+}
+
+void
+tty_hiwat_in_block(struct tty *tp)
+{
+
+	if ((tp->t_flags & TF_HIWAT_IN) == 0 &&
+	    tp->t_termios.c_iflag & IXOFF &&
+	    tp->t_termios.c_cc[VSTOP] != _POSIX_VDISABLE) {
+		/*
+		 * Input flow control. Only enter the high watermark when we
+		 * can successfully store the VSTOP character.
+		 */
+		if (ttyoutq_write_nofrag(&tp->t_outq,
+		    &tp->t_termios.c_cc[VSTOP], 1) == 0)
+			tp->t_flags |= TF_HIWAT_IN;
+	} else {
+		/* No input flow control. */
+		tp->t_flags |= TF_HIWAT_IN;
+	}
+}
+
+void
+tty_hiwat_in_unblock(struct tty *tp)
+{
+
+	if (tp->t_flags & TF_HIWAT_IN &&
+	    tp->t_termios.c_iflag & IXOFF &&
+	    tp->t_termios.c_cc[VSTART] != _POSIX_VDISABLE) {
+		/*
+		 * Input flow control. Only leave the high watermark when we
+		 * can successfully store the VSTART character.
+		 */
+		if (ttyoutq_write_nofrag(&tp->t_outq,
+		    &tp->t_termios.c_cc[VSTART], 1) == 0)
+			tp->t_flags &= ~TF_HIWAT_IN;
+	} else {
+		/* No input flow control. */
+		tp->t_flags &= ~TF_HIWAT_IN;
+	}
+
+	if (!tty_gone(tp))
+		ttydevsw_inwakeup(tp);
+}
+
+/*
+ * TTY hooks interface.
+ */
+
+static int
+ttyhook_defrint(struct tty *tp, char c, int flags)
+{
+
+	if (ttyhook_rint_bypass(tp, &c, 1) != 1)
+		return (-1);
+
+	return (0);
+}
+
+int
+ttyhook_register(struct tty **rtp, struct proc *p, int fd, struct ttyhook *th,
+    void *softc)
+{
+	struct tty *tp;
+	struct file *fp;
+	struct cdev *dev;
+	struct cdevsw *cdp;
+	struct filedesc *fdp;
+	cap_rights_t rights;
+	int error, ref;
+
+	/* Validate the file descriptor. */
+	fdp = p->p_fd;
+	error = fget_unlocked(fdp, fd, cap_rights_init(&rights, CAP_TTYHOOK),
+	    &fp, NULL);
+	if (error != 0)
+		return (error);
+	if (fp->f_ops == &badfileops) {
+		error = EBADF;
+		goto done1;
+	}
+
+	/*
+	 * Make sure the vnode is bound to a character device.
+	 * Unlocked check for the vnode type is ok there, because we
+	 * only shall prevent calling devvn_refthread on the file that
+	 * never has been opened over a character device.
+	 */
+	if (fp->f_type != DTYPE_VNODE || fp->f_vnode->v_type != VCHR) {
+		error = EINVAL;
+		goto done1;
+	}
+
+	/* Make sure it is a TTY. */
+	cdp = devvn_refthread(fp->f_vnode, &dev, &ref);
+	if (cdp == NULL) {
+		error = ENXIO;
+		goto done1;
+	}
+	if (dev != fp->f_data) {
+		error = ENXIO;
+		goto done2;
+	}
+	if (cdp != &ttydev_cdevsw) {
+		error = ENOTTY;
+		goto done2;
+	}
+	tp = dev->si_drv1;
+
+	/* Try to attach the hook to the TTY. */
+	error = EBUSY;
+	tty_lock(tp);
+	MPASS((tp->t_hook == NULL) == ((tp->t_flags & TF_HOOK) == 0));
+	if (tp->t_flags & TF_HOOK)
+		goto done3;
+
+	tp->t_flags |= TF_HOOK;
+	tp->t_hook = th;
+	tp->t_hooksoftc = softc;
+	*rtp = tp;
+	error = 0;
+
+	/* Maybe we can switch into bypass mode now. */
+	ttydisc_optimize(tp);
+
+	/* Silently convert rint() calls to rint_bypass() when possible. */
+	if (!ttyhook_hashook(tp, rint) && ttyhook_hashook(tp, rint_bypass))
+		th->th_rint = ttyhook_defrint;
+
+done3:	tty_unlock(tp);
+done2:	dev_relthread(dev, ref);
+done1:	fdrop(fp, curthread);
+	return (error);
+}
+
+void
+ttyhook_unregister(struct tty *tp)
+{
+
+	tty_lock_assert(tp, MA_OWNED);
+	MPASS(tp->t_flags & TF_HOOK);
+
+	/* Disconnect the hook. */
+	tp->t_flags &= ~TF_HOOK;
+	tp->t_hook = NULL;
+
+	/* Maybe we need to leave bypass mode. */
+	ttydisc_optimize(tp);
+
+	/* Maybe deallocate the TTY as well. */
+	tty_rel_free(tp);
+}
+
+/*
+ * /dev/console handling.
+ */
+
+static int
+ttyconsdev_open(struct cdev *dev, int oflags, int devtype, struct thread *td)
+{
+	struct tty *tp;
+
+	/* System has no console device. */
+	if (dev_console_filename == NULL)
+		return (ENXIO);
+
+	/* Look up corresponding TTY by device name. */
+	sx_slock(&tty_list_sx);
+	TAILQ_FOREACH(tp, &tty_list, t_list) {
+		if (strcmp(dev_console_filename, tty_devname(tp)) == 0) {
+			dev_console->si_drv1 = tp;
+			break;
+		}
+	}
+	sx_sunlock(&tty_list_sx);
+
+	/* System console has no TTY associated. */
+	if (dev_console->si_drv1 == NULL)
+		return (ENXIO);
+
+	return (ttydev_open(dev, oflags, devtype, td));
+}
+
+static int
+ttyconsdev_write(struct cdev *dev, struct uio *uio, int ioflag)
+{
+
+	log_console(uio);
+
+	return (ttydev_write(dev, uio, ioflag));
+}
+
+/*
+ * /dev/console is a little different than normal TTY's.  When opened,
+ * it determines which TTY to use.  When data gets written to it, it
+ * will be logged in the kernel message buffer.
+ */
+static struct cdevsw ttyconsdev_cdevsw = {
+	.d_version	= D_VERSION,
+	.d_open		= ttyconsdev_open,
+	.d_close	= ttydev_close,
+	.d_read		= ttydev_read,
+	.d_write	= ttyconsdev_write,
+	.d_ioctl	= ttydev_ioctl,
+	.d_kqfilter	= ttydev_kqfilter,
+	.d_poll		= ttydev_poll,
+	.d_mmap		= ttydev_mmap,
+	.d_name		= "ttyconsdev",
+	.d_flags	= D_TTY,
+};
+
+static void
+ttyconsdev_init(void *unused __unused)
+{
+
+	dev_console = make_dev_credf(MAKEDEV_ETERNAL, &ttyconsdev_cdevsw, 0,
+	    NULL, UID_ROOT, GID_WHEEL, 0600, "console");
+}
+
+SYSINIT(tty, SI_SUB_DRIVERS, SI_ORDER_FIRST, ttyconsdev_init, NULL);
+
+void
+ttyconsdev_select(const char *name)
+{
+
+	dev_console_filename = name;
+}
+
+/*
+ * Debugging routines.
+ */
+
+#include <rtems/bsd/local/opt_ddb.h>
+#ifdef DDB
+#include <ddb/ddb.h>
+#include <ddb/db_sym.h>
+
+static const struct {
+	int flag;
+	char val;
+} ttystates[] = {
+#if 0
+	{ TF_NOPREFIX,		'N' },
+#endif
+	{ TF_INITLOCK,		'I' },
+	{ TF_CALLOUT,		'C' },
+
+	/* Keep these together -> 'Oi' and 'Oo'. */
+	{ TF_OPENED,		'O' },
+	{ TF_OPENED_IN,		'i' },
+	{ TF_OPENED_OUT,	'o' },
+	{ TF_OPENED_CONS,	'c' },
+
+	{ TF_GONE,		'G' },
+	{ TF_OPENCLOSE,		'B' },
+	{ TF_ASYNC,		'Y' },
+	{ TF_LITERAL,		'L' },
+
+	/* Keep these together -> 'Hi' and 'Ho'. */
+	{ TF_HIWAT,		'H' },
+	{ TF_HIWAT_IN,		'i' },
+	{ TF_HIWAT_OUT,		'o' },
+
+	{ TF_STOPPED,		'S' },
+	{ TF_EXCLUDE,		'X' },
+	{ TF_BYPASS,		'l' },
+	{ TF_ZOMBIE,		'Z' },
+	{ TF_HOOK,		's' },
+
+	/* Keep these together -> 'bi' and 'bo'. */
+	{ TF_BUSY,		'b' },
+	{ TF_BUSY_IN,		'i' },
+	{ TF_BUSY_OUT,		'o' },
+
+	{ 0,			'\0'},
+};
+
+#define	TTY_FLAG_BITS \
+	"\20\1NOPREFIX\2INITLOCK\3CALLOUT\4OPENED_IN" \
+	"\5OPENED_OUT\6OPENED_CONS\7GONE\10OPENCLOSE" \
+	"\11ASYNC\12LITERAL\13HIWAT_IN\14HIWAT_OUT" \
+	"\15STOPPED\16EXCLUDE\17BYPASS\20ZOMBIE" \
+	"\21HOOK\22BUSY_IN\23BUSY_OUT"
+
+#define DB_PRINTSYM(name, addr) \
+	db_printf("%s  " #name ": ", sep); \
+	db_printsym((db_addr_t) addr, DB_STGY_ANY); \
+	db_printf("\n");
+
+static void
+_db_show_devsw(const char *sep, const struct ttydevsw *tsw)
+{
+
+	db_printf("%sdevsw: ", sep);
+	db_printsym((db_addr_t)tsw, DB_STGY_ANY);
+	db_printf(" (%p)\n", tsw);
+	DB_PRINTSYM(open, tsw->tsw_open);
+	DB_PRINTSYM(close, tsw->tsw_close);
+	DB_PRINTSYM(outwakeup, tsw->tsw_outwakeup);
+	DB_PRINTSYM(inwakeup, tsw->tsw_inwakeup);
+	DB_PRINTSYM(ioctl, tsw->tsw_ioctl);
+	DB_PRINTSYM(param, tsw->tsw_param);
+	DB_PRINTSYM(modem, tsw->tsw_modem);
+	DB_PRINTSYM(mmap, tsw->tsw_mmap);
+	DB_PRINTSYM(pktnotify, tsw->tsw_pktnotify);
+	DB_PRINTSYM(free, tsw->tsw_free);
+}
+
+static void
+_db_show_hooks(const char *sep, const struct ttyhook *th)
+{
+
+	db_printf("%shook: ", sep);
+	db_printsym((db_addr_t)th, DB_STGY_ANY);
+	db_printf(" (%p)\n", th);
+	if (th == NULL)
+		return;
+	DB_PRINTSYM(rint, th->th_rint);
+	DB_PRINTSYM(rint_bypass, th->th_rint_bypass);
+	DB_PRINTSYM(rint_done, th->th_rint_done);
+	DB_PRINTSYM(rint_poll, th->th_rint_poll);
+	DB_PRINTSYM(getc_inject, th->th_getc_inject);
+	DB_PRINTSYM(getc_capture, th->th_getc_capture);
+	DB_PRINTSYM(getc_poll, th->th_getc_poll);
+	DB_PRINTSYM(close, th->th_close);
+}
+
+static void
+_db_show_termios(const char *name, const struct termios *t)
+{
+
+	db_printf("%s: iflag 0x%x oflag 0x%x cflag 0x%x "
+	    "lflag 0x%x ispeed %u ospeed %u\n", name,
+	    t->c_iflag, t->c_oflag, t->c_cflag, t->c_lflag,
+	    t->c_ispeed, t->c_ospeed);
+}
+
+/* DDB command to show TTY statistics. */
+DB_SHOW_COMMAND(tty, db_show_tty)
+{
+	struct tty *tp;
+
+	if (!have_addr) {
+		db_printf("usage: show tty <addr>\n");
+		return;
+	}
+	tp = (struct tty *)addr;
+
+	db_printf("%p: %s\n", tp, tty_devname(tp));
+	db_printf("\tmtx: %p\n", tp->t_mtx);
+	db_printf("\tflags: 0x%b\n", tp->t_flags, TTY_FLAG_BITS);
+	db_printf("\trevokecnt: %u\n", tp->t_revokecnt);
+
+	/* Buffering mechanisms. */
+	db_printf("\tinq: %p begin %u linestart %u reprint %u end %u "
+	    "nblocks %u quota %u\n", &tp->t_inq, tp->t_inq.ti_begin,
+	    tp->t_inq.ti_linestart, tp->t_inq.ti_reprint, tp->t_inq.ti_end,
+	    tp->t_inq.ti_nblocks, tp->t_inq.ti_quota);
+	db_printf("\toutq: %p begin %u end %u nblocks %u quota %u\n",
+	    &tp->t_outq, tp->t_outq.to_begin, tp->t_outq.to_end,
+	    tp->t_outq.to_nblocks, tp->t_outq.to_quota);
+	db_printf("\tinlow: %zu\n", tp->t_inlow);
+	db_printf("\toutlow: %zu\n", tp->t_outlow);
+	_db_show_termios("\ttermios", &tp->t_termios);
+	db_printf("\twinsize: row %u col %u xpixel %u ypixel %u\n",
+	    tp->t_winsize.ws_row, tp->t_winsize.ws_col,
+	    tp->t_winsize.ws_xpixel, tp->t_winsize.ws_ypixel);
+	db_printf("\tcolumn: %u\n", tp->t_column);
+	db_printf("\twritepos: %u\n", tp->t_writepos);
+	db_printf("\tcompatflags: 0x%x\n", tp->t_compatflags);
+
+	/* Init/lock-state devices. */
+	_db_show_termios("\ttermios_init_in", &tp->t_termios_init_in);
+	_db_show_termios("\ttermios_init_out", &tp->t_termios_init_out);
+	_db_show_termios("\ttermios_lock_in", &tp->t_termios_lock_in);
+	_db_show_termios("\ttermios_lock_out", &tp->t_termios_lock_out);
+
+	/* Hooks */
+	_db_show_devsw("\t", tp->t_devsw);
+	_db_show_hooks("\t", tp->t_hook);
+
+	/* Process info. */
+	db_printf("\tpgrp: %p gid %d jobc %d\n", tp->t_pgrp,
+	    tp->t_pgrp ? tp->t_pgrp->pg_id : 0,
+	    tp->t_pgrp ? tp->t_pgrp->pg_jobc : 0);
+	db_printf("\tsession: %p", tp->t_session);
+	if (tp->t_session != NULL)
+	    db_printf(" count %u leader %p tty %p sid %d login %s",
+		tp->t_session->s_count, tp->t_session->s_leader,
+		tp->t_session->s_ttyp, tp->t_session->s_sid,
+		tp->t_session->s_login);
+	db_printf("\n");
+	db_printf("\tsessioncnt: %u\n", tp->t_sessioncnt);
+	db_printf("\tdevswsoftc: %p\n", tp->t_devswsoftc);
+	db_printf("\thooksoftc: %p\n", tp->t_hooksoftc);
+	db_printf("\tdev: %p\n", tp->t_dev);
+}
+
+/* DDB command to list TTYs. */
+DB_SHOW_ALL_COMMAND(ttys, db_show_all_ttys)
+{
+	struct tty *tp;
+	size_t isiz, osiz;
+	int i, j;
+
+	/* Make the output look like `pstat -t'. */
+	db_printf("PTR        ");
+#if defined(__LP64__)
+	db_printf("        ");
+#endif
+	db_printf("      LINE   INQ  CAN  LIN  LOW  OUTQ  USE  LOW   "
+	    "COL  SESS  PGID STATE\n");
+
+	TAILQ_FOREACH(tp, &tty_list, t_list) {
+		isiz = tp->t_inq.ti_nblocks * TTYINQ_DATASIZE;
+		osiz = tp->t_outq.to_nblocks * TTYOUTQ_DATASIZE;
+
+		db_printf("%p %10s %5zu %4u %4u %4zu %5zu %4u %4zu %5u %5d "
+		    "%5d ", tp, tty_devname(tp), isiz,
+		    tp->t_inq.ti_linestart - tp->t_inq.ti_begin,
+		    tp->t_inq.ti_end - tp->t_inq.ti_linestart,
+		    isiz - tp->t_inlow, osiz,
+		    tp->t_outq.to_end - tp->t_outq.to_begin,
+		    osiz - tp->t_outlow, MIN(tp->t_column, 99999),
+		    tp->t_session ? tp->t_session->s_sid : 0,
+		    tp->t_pgrp ? tp->t_pgrp->pg_id : 0);
+
+		/* Flag bits. */
+		for (i = j = 0; ttystates[i].flag; i++)
+			if (tp->t_flags & ttystates[i].flag) {
+				db_printf("%c", ttystates[i].val);
+				j++;
+			}
+		if (j == 0)
+			db_printf("-");
+		db_printf("\n");
+	}
+}
+#endif /* DDB */
diff --git a/freebsd/sys/kern/tty_inq.c b/freebsd/sys/kern/tty_inq.c
new file mode 100644
index 00000000..0093cb31
--- /dev/null
+++ b/freebsd/sys/kern/tty_inq.c
@@ -0,0 +1,497 @@
+#include <machine/rtems-bsd-kernel-space.h>
+
+/*-
+ * Copyright (c) 2008 Ed Schouten <ed@FreeBSD.org>
+ * All rights reserved.
+ *
+ * Portions of this software were developed under sponsorship from Snow
+ * B.V., the Netherlands.
+ *
+ * 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.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <rtems/bsd/sys/param.h>
+#include <sys/kernel.h>
+#include <rtems/bsd/sys/lock.h>
+#include <sys/queue.h>
+#include <sys/sysctl.h>
+#include <sys/systm.h>
+#include <sys/tty.h>
+#include <sys/uio.h>
+
+#include <vm/uma.h>
+
+/*
+ * TTY input queue buffering.
+ *
+ * Unlike the output queue, the input queue has more features that are
+ * needed to properly implement various features offered by the TTY
+ * interface:
+ *
+ * - Data can be removed from the tail of the queue, which is used to
+ *   implement backspace.
+ * - Once in a while, input has to be `canonicalized'. When ICANON is
+ *   turned on, this will be done after a CR has been inserted.
+ *   Otherwise, it should be done after any character has been inserted.
+ * - The input queue can store one bit per byte, called the quoting bit.
+ *   This bit is used by TTYDISC to make backspace work on quoted
+ *   characters.
+ *
+ * In most cases, there is probably less input than output, so unlike
+ * the outq, we'll stick to 128 byte blocks here.
+ */
+
+static int ttyinq_flush_secure = 1;
+SYSCTL_INT(_kern, OID_AUTO, tty_inq_flush_secure, CTLFLAG_RW,
+	&ttyinq_flush_secure, 0, "Zero buffers while flushing");
+
+#define TTYINQ_QUOTESIZE	(TTYINQ_DATASIZE / BMSIZE)
+#define BMSIZE			32
+#define GETBIT(tib,boff) \
+	((tib)->tib_quotes[(boff) / BMSIZE] & (1 << ((boff) % BMSIZE)))
+#define SETBIT(tib,boff) \
+	((tib)->tib_quotes[(boff) / BMSIZE] |= (1 << ((boff) % BMSIZE)))
+#define CLRBIT(tib,boff) \
+	((tib)->tib_quotes[(boff) / BMSIZE] &= ~(1 << ((boff) % BMSIZE)))
+
+struct ttyinq_block {
+	struct ttyinq_block	*tib_prev;
+	struct ttyinq_block	*tib_next;
+	uint32_t		tib_quotes[TTYINQ_QUOTESIZE];
+	char			tib_data[TTYINQ_DATASIZE];
+};
+
+static uma_zone_t ttyinq_zone;
+
+#define	TTYINQ_INSERT_TAIL(ti, tib) do {				\
+	if (ti->ti_end == 0) {						\
+		tib->tib_prev = NULL;					\
+		tib->tib_next = ti->ti_firstblock;			\
+		ti->ti_firstblock = tib;				\
+	} else {							\
+		tib->tib_prev = ti->ti_lastblock;			\
+		tib->tib_next = ti->ti_lastblock->tib_next;		\
+		ti->ti_lastblock->tib_next = tib;			\
+	}								\
+	if (tib->tib_next != NULL)					\
+		tib->tib_next->tib_prev = tib;				\
+	ti->ti_nblocks++;						\
+} while (0)
+
+#define	TTYINQ_REMOVE_HEAD(ti) do {					\
+	ti->ti_firstblock = ti->ti_firstblock->tib_next;		\
+	if (ti->ti_firstblock != NULL)					\
+		ti->ti_firstblock->tib_prev = NULL;			\
+	ti->ti_nblocks--;						\
+} while (0)
+
+#define	TTYINQ_RECYCLE(ti, tib) do {					\
+	if (ti->ti_quota <= ti->ti_nblocks)				\
+		uma_zfree(ttyinq_zone, tib);				\
+	else								\
+		TTYINQ_INSERT_TAIL(ti, tib);				\
+} while (0)
+
+int
+ttyinq_setsize(struct ttyinq *ti, struct tty *tp, size_t size)
+{
+	struct ttyinq_block *tib;
+
+	ti->ti_quota = howmany(size, TTYINQ_DATASIZE);
+
+	while (ti->ti_quota > ti->ti_nblocks) {
+		/*
+		 * List is getting bigger.
+		 * Add new blocks to the tail of the list.
+		 *
+		 * We must unlock the TTY temporarily, because we need
+		 * to allocate memory. This won't be a problem, because
+		 * in the worst case, another thread ends up here, which
+		 * may cause us to allocate too many blocks, but this
+		 * will be caught by the loop below.
+		 */
+		tty_unlock(tp);
+		tib = uma_zalloc(ttyinq_zone, M_WAITOK);
+		tty_lock(tp);
+
+		if (tty_gone(tp)) {
+			uma_zfree(ttyinq_zone, tib);
+			return (ENXIO);
+		}
+
+		TTYINQ_INSERT_TAIL(ti, tib);
+	}
+	return (0);
+}
+
+void
+ttyinq_free(struct ttyinq *ti)
+{
+	struct ttyinq_block *tib;
+
+	ttyinq_flush(ti);
+	ti->ti_quota = 0;
+
+	while ((tib = ti->ti_firstblock) != NULL) {
+		TTYINQ_REMOVE_HEAD(ti);
+		uma_zfree(ttyinq_zone, tib);
+	}
+
+	MPASS(ti->ti_nblocks == 0);
+}
+
+int
+ttyinq_read_uio(struct ttyinq *ti, struct tty *tp, struct uio *uio,
+    size_t rlen, size_t flen)
+{
+
+	MPASS(rlen <= uio->uio_resid);
+
+	while (rlen > 0) {
+		int error;
+		struct ttyinq_block *tib;
+		size_t cbegin, cend, clen;
+
+		/* See if there still is data. */
+		if (ti->ti_begin == ti->ti_linestart)
+			return (0);
+		tib = ti->ti_firstblock;
+		if (tib == NULL)
+			return (0);
+
+		/*
+		 * The end address should be the lowest of these three:
+		 * - The write pointer
+		 * - The blocksize - we can't read beyond the block
+		 * - The end address if we could perform the full read
+		 */
+		cbegin = ti->ti_begin;
+		cend = MIN(MIN(ti->ti_linestart, ti->ti_begin + rlen),
+		    TTYINQ_DATASIZE);
+		clen = cend - cbegin;
+		MPASS(clen >= flen);
+		rlen -= clen;
+
+		/*
+		 * We can prevent buffering in some cases:
+		 * - We need to read the block until the end.
+		 * - We don't need to read the block until the end, but
+		 *   there is no data beyond it, which allows us to move
+		 *   the write pointer to a new block.
+		 */
+		if (cend == TTYINQ_DATASIZE || cend == ti->ti_end) {
+			/*
+			 * Fast path: zero copy. Remove the first block,
+			 * so we can unlock the TTY temporarily.
+			 */
+			TTYINQ_REMOVE_HEAD(ti);
+			ti->ti_begin = 0;
+
+			/*
+			 * Because we remove the first block, we must
+			 * fix up the block offsets.
+			 */
+#define CORRECT_BLOCK(t) do {			\
+	if (t <= TTYINQ_DATASIZE)		\
+		t = 0;				\
+	else					\
+		t -= TTYINQ_DATASIZE;		\
+} while (0)
+			CORRECT_BLOCK(ti->ti_linestart);
+			CORRECT_BLOCK(ti->ti_reprint);
+			CORRECT_BLOCK(ti->ti_end);
+#undef CORRECT_BLOCK
+
+			/*
+			 * Temporary unlock and copy the data to
+			 * userspace. We may need to flush trailing
+			 * bytes, like EOF characters.
+			 */
+			tty_unlock(tp);
+			error = uiomove(tib->tib_data + cbegin,
+			    clen - flen, uio);
+			tty_lock(tp);
+
+			/* Block can now be readded to the list. */
+			TTYINQ_RECYCLE(ti, tib);
+		} else {
+			char ob[TTYINQ_DATASIZE - 1];
+
+			/*
+			 * Slow path: store data in a temporary buffer.
+			 */
+			memcpy(ob, tib->tib_data + cbegin, clen - flen);
+			ti->ti_begin += clen;
+			MPASS(ti->ti_begin < TTYINQ_DATASIZE);
+
+			/* Temporary unlock and copy the data to userspace. */
+			tty_unlock(tp);
+			error = uiomove(ob, clen - flen, uio);
+			tty_lock(tp);
+		}
+
+		if (error != 0)
+			return (error);
+		if (tty_gone(tp))
+			return (ENXIO);
+	}
+
+	return (0);
+}
+
+static __inline void
+ttyinq_set_quotes(struct ttyinq_block *tib, size_t offset,
+    size_t length, int value)
+{
+
+	if (value) {
+		/* Set the bits. */
+		for (; length > 0; length--, offset++)
+			SETBIT(tib, offset);
+	} else {
+		/* Unset the bits. */
+		for (; length > 0; length--, offset++)
+			CLRBIT(tib, offset);
+	}
+}
+
+size_t
+ttyinq_write(struct ttyinq *ti, const void *buf, size_t nbytes, int quote)
+{
+	const char *cbuf = buf;
+	struct ttyinq_block *tib;
+	unsigned int boff;
+	size_t l;
+
+	while (nbytes > 0) {
+		boff = ti->ti_end % TTYINQ_DATASIZE;
+
+		if (ti->ti_end == 0) {
+			/* First time we're being used or drained. */
+			MPASS(ti->ti_begin == 0);
+			tib = ti->ti_firstblock;
+			if (tib == NULL) {
+				/* Queue has no blocks. */
+				break;
+			}
+			ti->ti_lastblock = tib;
+		} else if (boff == 0) {
+			/* We reached the end of this block on last write. */
+			tib = ti->ti_lastblock->tib_next;
+			if (tib == NULL) {
+				/* We've reached the watermark. */
+				break;
+			}
+			ti->ti_lastblock = tib;
+		} else {
+			tib = ti->ti_lastblock;
+		}
+
+		/* Don't copy more than was requested. */
+		l = MIN(nbytes, TTYINQ_DATASIZE - boff);
+		MPASS(l > 0);
+		memcpy(tib->tib_data + boff, cbuf, l);
+
+		/* Set the quoting bits for the proper region. */
+		ttyinq_set_quotes(tib, boff, l, quote);
+
+		cbuf += l;
+		nbytes -= l;
+		ti->ti_end += l;
+	}
+
+	return (cbuf - (const char *)buf);
+}
+
+int
+ttyinq_write_nofrag(struct ttyinq *ti, const void *buf, size_t nbytes, int quote)
+{
+	size_t ret;
+
+	if (ttyinq_bytesleft(ti) < nbytes)
+		return (-1);
+
+	/* We should always be able to write it back. */
+	ret = ttyinq_write(ti, buf, nbytes, quote);
+	MPASS(ret == nbytes);
+
+	return (0);
+}
+
+void
+ttyinq_canonicalize(struct ttyinq *ti)
+{
+
+	ti->ti_linestart = ti->ti_reprint = ti->ti_end;
+	ti->ti_startblock = ti->ti_reprintblock = ti->ti_lastblock;
+}
+
+size_t
+ttyinq_findchar(struct ttyinq *ti, const char *breakc, size_t maxlen,
+    char *lastc)
+{
+	struct ttyinq_block *tib = ti->ti_firstblock;
+	unsigned int boff = ti->ti_begin;
+	unsigned int bend = MIN(MIN(TTYINQ_DATASIZE, ti->ti_linestart),
+	    ti->ti_begin + maxlen);
+
+	MPASS(maxlen > 0);
+
+	if (tib == NULL)
+		return (0);
+
+	while (boff < bend) {
+		if (strchr(breakc, tib->tib_data[boff]) && !GETBIT(tib, boff)) {
+			*lastc = tib->tib_data[boff];
+			return (boff - ti->ti_begin + 1);
+		}
+		boff++;
+	}
+
+	/* Not found - just process the entire block. */
+	return (bend - ti->ti_begin);
+}
+
+void
+ttyinq_flush(struct ttyinq *ti)
+{
+	struct ttyinq_block *tib;
+
+	ti->ti_begin = 0;
+	ti->ti_linestart = 0;
+	ti->ti_reprint = 0;
+	ti->ti_end = 0;
+
+	/* Zero all data in the input queue to get rid of passwords. */
+	if (ttyinq_flush_secure) {
+		for (tib = ti->ti_firstblock; tib != NULL; tib = tib->tib_next)
+			bzero(&tib->tib_data, sizeof tib->tib_data);
+	}
+}
+
+int
+ttyinq_peekchar(struct ttyinq *ti, char *c, int *quote)
+{
+	unsigned int boff;
+	struct ttyinq_block *tib = ti->ti_lastblock;
+
+	if (ti->ti_linestart == ti->ti_end)
+		return (-1);
+
+	MPASS(ti->ti_end > 0);
+	boff = (ti->ti_end - 1) % TTYINQ_DATASIZE;
+
+	*c = tib->tib_data[boff];
+	*quote = GETBIT(tib, boff);
+
+	return (0);
+}
+
+void
+ttyinq_unputchar(struct ttyinq *ti)
+{
+
+	MPASS(ti->ti_linestart < ti->ti_end);
+
+	if (--ti->ti_end % TTYINQ_DATASIZE == 0) {
+		/* Roll back to the previous block. */
+		ti->ti_lastblock = ti->ti_lastblock->tib_prev;
+		/*
+		 * This can only fail if we are unputchar()'ing the
+		 * first character in the queue.
+		 */
+		MPASS((ti->ti_lastblock == NULL) == (ti->ti_end == 0));
+	}
+}
+
+void
+ttyinq_reprintpos_set(struct ttyinq *ti)
+{
+
+	ti->ti_reprint = ti->ti_end;
+	ti->ti_reprintblock = ti->ti_lastblock;
+}
+
+void
+ttyinq_reprintpos_reset(struct ttyinq *ti)
+{
+
+	ti->ti_reprint = ti->ti_linestart;
+	ti->ti_reprintblock = ti->ti_startblock;
+}
+
+static void
+ttyinq_line_iterate(struct ttyinq *ti,
+    ttyinq_line_iterator_t *iterator, void *data,
+    unsigned int offset, struct ttyinq_block *tib)
+{
+	unsigned int boff;
+
+	/* Use the proper block when we're at the queue head. */
+	if (offset == 0)
+		tib = ti->ti_firstblock;
+
+	/* Iterate all characters and call the iterator function. */
+	for (; offset < ti->ti_end; offset++) {
+		boff = offset % TTYINQ_DATASIZE;
+		MPASS(tib != NULL);
+
+		/* Call back the iterator function. */
+		iterator(data, tib->tib_data[boff], GETBIT(tib, boff));
+
+		/* Last byte iterated - go to the next block. */
+		if (boff == TTYINQ_DATASIZE - 1)
+			tib = tib->tib_next;
+		MPASS(tib != NULL);
+	}
+}
+
+void
+ttyinq_line_iterate_from_linestart(struct ttyinq *ti,
+    ttyinq_line_iterator_t *iterator, void *data)
+{
+
+	ttyinq_line_iterate(ti, iterator, data,
+	    ti->ti_linestart, ti->ti_startblock);
+}
+
+void
+ttyinq_line_iterate_from_reprintpos(struct ttyinq *ti,
+    ttyinq_line_iterator_t *iterator, void *data)
+{
+
+	ttyinq_line_iterate(ti, iterator, data,
+	    ti->ti_reprint, ti->ti_reprintblock);
+}
+
+static void
+ttyinq_startup(void *dummy)
+{
+
+	ttyinq_zone = uma_zcreate("ttyinq", sizeof(struct ttyinq_block),
+	    NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
+}
+
+SYSINIT(ttyinq, SI_SUB_DRIVERS, SI_ORDER_FIRST, ttyinq_startup, NULL);
diff --git a/freebsd/sys/kern/tty_outq.c b/freebsd/sys/kern/tty_outq.c
new file mode 100644
index 00000000..b6bc96d5
--- /dev/null
+++ b/freebsd/sys/kern/tty_outq.c
@@ -0,0 +1,347 @@
+#include <machine/rtems-bsd-kernel-space.h>
+
+/*-
+ * Copyright (c) 2008 Ed Schouten <ed@FreeBSD.org>
+ * All rights reserved.
+ *
+ * Portions of this software were developed under sponsorship from Snow
+ * B.V., the Netherlands.
+ *
+ * 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.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <rtems/bsd/sys/param.h>
+#include <sys/kernel.h>
+#include <rtems/bsd/sys/lock.h>
+#include <sys/queue.h>
+#include <sys/systm.h>
+#include <sys/tty.h>
+#include <sys/uio.h>
+
+#include <vm/uma.h>
+
+/*
+ * TTY output queue buffering.
+ *
+ * The previous design of the TTY layer offered the so-called clists.
+ * These clists were used for both the input queues and the output
+ * queue. We don't use certain features on the output side, like quoting
+ * bits for parity marking and such. This mechanism is similar to the
+ * old clists, but only contains the features we need to buffer the
+ * output.
+ */
+
+struct ttyoutq_block {
+	struct ttyoutq_block	*tob_next;
+	char			tob_data[TTYOUTQ_DATASIZE];
+};
+
+static uma_zone_t ttyoutq_zone;
+
+#define	TTYOUTQ_INSERT_TAIL(to, tob) do {				\
+	if (to->to_end == 0) {						\
+		tob->tob_next = to->to_firstblock;			\
+		to->to_firstblock = tob;				\
+	} else {							\
+		tob->tob_next = to->to_lastblock->tob_next;		\
+		to->to_lastblock->tob_next = tob;			\
+	}								\
+	to->to_nblocks++;						\
+} while (0)
+
+#define	TTYOUTQ_REMOVE_HEAD(to) do {					\
+	to->to_firstblock = to->to_firstblock->tob_next;		\
+	to->to_nblocks--;						\
+} while (0)
+
+#define	TTYOUTQ_RECYCLE(to, tob) do {					\
+	if (to->to_quota <= to->to_nblocks)				\
+		uma_zfree(ttyoutq_zone, tob);				\
+	else								\
+		TTYOUTQ_INSERT_TAIL(to, tob);				\
+} while(0)
+
+void
+ttyoutq_flush(struct ttyoutq *to)
+{
+
+	to->to_begin = 0;
+	to->to_end = 0;
+}
+
+int
+ttyoutq_setsize(struct ttyoutq *to, struct tty *tp, size_t size)
+{
+	struct ttyoutq_block *tob;
+
+	to->to_quota = howmany(size, TTYOUTQ_DATASIZE);
+
+	while (to->to_quota > to->to_nblocks) {
+		/*
+		 * List is getting bigger.
+		 * Add new blocks to the tail of the list.
+		 *
+		 * We must unlock the TTY temporarily, because we need
+		 * to allocate memory. This won't be a problem, because
+		 * in the worst case, another thread ends up here, which
+		 * may cause us to allocate too many blocks, but this
+		 * will be caught by the loop below.
+		 */
+		tty_unlock(tp);
+		tob = uma_zalloc(ttyoutq_zone, M_WAITOK);
+		tty_lock(tp);
+
+		if (tty_gone(tp)) {
+			uma_zfree(ttyoutq_zone, tob);
+			return (ENXIO);
+		}
+
+		TTYOUTQ_INSERT_TAIL(to, tob);
+	}
+	return (0);
+}
+
+void
+ttyoutq_free(struct ttyoutq *to)
+{
+	struct ttyoutq_block *tob;
+
+	ttyoutq_flush(to);
+	to->to_quota = 0;
+
+	while ((tob = to->to_firstblock) != NULL) {
+		TTYOUTQ_REMOVE_HEAD(to);
+		uma_zfree(ttyoutq_zone, tob);
+	}
+
+	MPASS(to->to_nblocks == 0);
+}
+
+size_t
+ttyoutq_read(struct ttyoutq *to, void *buf, size_t len)
+{
+	char *cbuf = buf;
+
+	while (len > 0) {
+		struct ttyoutq_block *tob;
+		size_t cbegin, cend, clen;
+
+		/* See if there still is data. */
+		if (to->to_begin == to->to_end)
+			break;
+		tob = to->to_firstblock;
+		if (tob == NULL)
+			break;
+
+		/*
+		 * The end address should be the lowest of these three:
+		 * - The write pointer
+		 * - The blocksize - we can't read beyond the block
+		 * - The end address if we could perform the full read
+		 */
+		cbegin = to->to_begin;
+		cend = MIN(MIN(to->to_end, to->to_begin + len),
+		    TTYOUTQ_DATASIZE);
+		clen = cend - cbegin;
+
+		/* Copy the data out of the buffers. */
+		memcpy(cbuf, tob->tob_data + cbegin, clen);
+		cbuf += clen;
+		len -= clen;
+
+		if (cend == to->to_end) {
+			/* Read the complete queue. */
+			to->to_begin = 0;
+			to->to_end = 0;
+		} else if (cend == TTYOUTQ_DATASIZE) {
+			/* Read the block until the end. */
+			TTYOUTQ_REMOVE_HEAD(to);
+			to->to_begin = 0;
+			to->to_end -= TTYOUTQ_DATASIZE;
+			TTYOUTQ_RECYCLE(to, tob);
+		} else {
+			/* Read the block partially. */
+			to->to_begin += clen;
+		}
+	}
+
+	return (cbuf - (char *)buf);
+}
+
+/*
+ * An optimized version of ttyoutq_read() which can be used in pseudo
+ * TTY drivers to directly copy data from the outq to userspace, instead
+ * of buffering it.
+ *
+ * We can only copy data directly if we need to read the entire block
+ * back to the user, because we temporarily remove the block from the
+ * queue. Otherwise we need to copy it to a temporary buffer first, to
+ * make sure data remains in the correct order.
+ */
+int
+ttyoutq_read_uio(struct ttyoutq *to, struct tty *tp, struct uio *uio)
+{
+
+	while (uio->uio_resid > 0) {
+		int error;
+		struct ttyoutq_block *tob;
+		size_t cbegin, cend, clen;
+
+		/* See if there still is data. */
+		if (to->to_begin == to->to_end)
+			return (0);
+		tob = to->to_firstblock;
+		if (tob == NULL)
+			return (0);
+
+		/*
+		 * The end address should be the lowest of these three:
+		 * - The write pointer
+		 * - The blocksize - we can't read beyond the block
+		 * - The end address if we could perform the full read
+		 */
+		cbegin = to->to_begin;
+		cend = MIN(MIN(to->to_end, to->to_begin + uio->uio_resid),
+		    TTYOUTQ_DATASIZE);
+		clen = cend - cbegin;
+
+		/*
+		 * We can prevent buffering in some cases:
+		 * - We need to read the block until the end.
+		 * - We don't need to read the block until the end, but
+		 *   there is no data beyond it, which allows us to move
+		 *   the write pointer to a new block.
+		 */
+		if (cend == TTYOUTQ_DATASIZE || cend == to->to_end) {
+			/*
+			 * Fast path: zero copy. Remove the first block,
+			 * so we can unlock the TTY temporarily.
+			 */
+			TTYOUTQ_REMOVE_HEAD(to);
+			to->to_begin = 0;
+			if (to->to_end <= TTYOUTQ_DATASIZE)
+				to->to_end = 0;
+			else
+				to->to_end -= TTYOUTQ_DATASIZE;
+
+			/* Temporary unlock and copy the data to userspace. */
+			tty_unlock(tp);
+			error = uiomove(tob->tob_data + cbegin, clen, uio);
+			tty_lock(tp);
+
+			/* Block can now be readded to the list. */
+			TTYOUTQ_RECYCLE(to, tob);
+		} else {
+			char ob[TTYOUTQ_DATASIZE - 1];
+
+			/*
+			 * Slow path: store data in a temporary buffer.
+			 */
+			memcpy(ob, tob->tob_data + cbegin, clen);
+			to->to_begin += clen;
+			MPASS(to->to_begin < TTYOUTQ_DATASIZE);
+
+			/* Temporary unlock and copy the data to userspace. */
+			tty_unlock(tp);
+			error = uiomove(ob, clen, uio);
+			tty_lock(tp);
+		}
+
+		if (error != 0)
+			return (error);
+	}
+
+	return (0);
+}
+
+size_t
+ttyoutq_write(struct ttyoutq *to, const void *buf, size_t nbytes)
+{
+	const char *cbuf = buf;
+	struct ttyoutq_block *tob;
+	unsigned int boff;
+	size_t l;
+
+	while (nbytes > 0) {
+		boff = to->to_end % TTYOUTQ_DATASIZE;
+
+		if (to->to_end == 0) {
+			/* First time we're being used or drained. */
+			MPASS(to->to_begin == 0);
+			tob = to->to_firstblock;
+			if (tob == NULL) {
+				/* Queue has no blocks. */
+				break;
+			}
+			to->to_lastblock = tob;
+		} else if (boff == 0) {
+			/* We reached the end of this block on last write. */
+			tob = to->to_lastblock->tob_next;
+			if (tob == NULL) {
+				/* We've reached the watermark. */
+				break;
+			}
+			to->to_lastblock = tob;
+		} else {
+			tob = to->to_lastblock;
+		}
+
+		/* Don't copy more than was requested. */
+		l = MIN(nbytes, TTYOUTQ_DATASIZE - boff);
+		MPASS(l > 0);
+		memcpy(tob->tob_data + boff, cbuf, l);
+
+		cbuf += l;
+		nbytes -= l;
+		to->to_end += l;
+	}
+
+	return (cbuf - (const char *)buf);
+}
+
+int
+ttyoutq_write_nofrag(struct ttyoutq *to, const void *buf, size_t nbytes)
+{
+	size_t ret;
+
+	if (ttyoutq_bytesleft(to) < nbytes)
+		return (-1);
+
+	/* We should always be able to write it back. */
+	ret = ttyoutq_write(to, buf, nbytes);
+	MPASS(ret == nbytes);
+
+	return (0);
+}
+
+static void
+ttyoutq_startup(void *dummy)
+{
+
+	ttyoutq_zone = uma_zcreate("ttyoutq", sizeof(struct ttyoutq_block),
+	    NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
+}
+
+SYSINIT(ttyoutq, SI_SUB_DRIVERS, SI_ORDER_FIRST, ttyoutq_startup, NULL);
diff --git a/freebsd/sys/kern/tty_ttydisc.c b/freebsd/sys/kern/tty_ttydisc.c
new file mode 100644
index 00000000..edb1d155
--- /dev/null
+++ b/freebsd/sys/kern/tty_ttydisc.c
@@ -0,0 +1,1267 @@
+#include <machine/rtems-bsd-kernel-space.h>
+
+/*-
+ * Copyright (c) 2008 Ed Schouten <ed@FreeBSD.org>
+ * All rights reserved.
+ *
+ * Portions of this software were developed under sponsorship from Snow
+ * B.V., the Netherlands.
+ *
+ * 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.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <rtems/bsd/sys/param.h>
+#include <sys/fcntl.h>
+#include <sys/filio.h>
+#include <sys/kernel.h>
+#include <sys/signal.h>
+#include <sys/sysctl.h>
+#include <sys/systm.h>
+#include <sys/tty.h>
+#include <sys/ttycom.h>
+#include <sys/ttydefaults.h>
+#include <sys/uio.h>
+#include <sys/vnode.h>
+
+/*
+ * Standard TTYDISC `termios' line discipline.
+ */
+
+/* Statistics. */
+static unsigned long tty_nin = 0;
+SYSCTL_ULONG(_kern, OID_AUTO, tty_nin, CTLFLAG_RD,
+	&tty_nin, 0, "Total amount of bytes received");
+static unsigned long tty_nout = 0;
+SYSCTL_ULONG(_kern, OID_AUTO, tty_nout, CTLFLAG_RD,
+	&tty_nout, 0, "Total amount of bytes transmitted");
+
+/* termios comparison macro's. */
+#define	CMP_CC(v,c) (tp->t_termios.c_cc[v] != _POSIX_VDISABLE && \
+			tp->t_termios.c_cc[v] == (c))
+#define	CMP_FLAG(field,opt) (tp->t_termios.c_ ## field ## flag & (opt))
+
+/* Characters that cannot be modified through c_cc. */
+#define CTAB	'\t'
+#define CNL	'\n'
+#define CCR	'\r'
+
+/* Character is a control character. */
+#define CTL_VALID(c)	((c) == 0x7f || (unsigned char)(c) < 0x20)
+/* Control character should be processed on echo. */
+#define CTL_ECHO(c,q)	(!(q) && ((c) == CERASE2 || (c) == CTAB || \
+    (c) == CNL || (c) == CCR))
+/* Control character should be printed using ^X notation. */
+#define CTL_PRINT(c,q)	((c) == 0x7f || ((unsigned char)(c) < 0x20 && \
+    ((q) || ((c) != CTAB && (c) != CNL))))
+/* Character is whitespace. */
+#define CTL_WHITE(c)	((c) == ' ' || (c) == CTAB)
+/* Character is alphanumeric. */
+#define CTL_ALNUM(c)	(((c) >= '0' && (c) <= '9') || \
+    ((c) >= 'a' && (c) <= 'z') || ((c) >= 'A' && (c) <= 'Z'))
+
+#define	TTY_STACKBUF	256
+
+void
+ttydisc_open(struct tty *tp)
+{
+	ttydisc_optimize(tp);
+}
+
+void
+ttydisc_close(struct tty *tp)
+{
+
+	/* Clean up our flags when leaving the discipline. */
+	tp->t_flags &= ~(TF_STOPPED|TF_HIWAT|TF_ZOMBIE);
+
+	/*
+	 * POSIX states that we must drain output and flush input on
+	 * last close.  Draining has already been done if possible.
+	 */
+	tty_flush(tp, FREAD | FWRITE);
+
+	if (ttyhook_hashook(tp, close))
+		ttyhook_close(tp);
+}
+
+static int
+ttydisc_read_canonical(struct tty *tp, struct uio *uio, int ioflag)
+{
+	char breakc[4] = { CNL }; /* enough to hold \n, VEOF and VEOL. */
+	int error;
+	size_t clen, flen = 0, n = 1;
+	unsigned char lastc = _POSIX_VDISABLE;
+
+#define BREAK_ADD(c) do { \
+	if (tp->t_termios.c_cc[c] != _POSIX_VDISABLE)	\
+		breakc[n++] = tp->t_termios.c_cc[c];	\
+} while (0)
+	/* Determine which characters we should trigger on. */
+	BREAK_ADD(VEOF);
+	BREAK_ADD(VEOL);
+#undef BREAK_ADD
+	breakc[n] = '\0';
+
+	do {
+		error = tty_wait_background(tp, curthread, SIGTTIN);
+		if (error)
+			return (error);
+
+		/*
+		 * Quite a tricky case: unlike the old TTY
+		 * implementation, this implementation copies data back
+		 * to userspace in large chunks. Unfortunately, we can't
+		 * calculate the line length on beforehand if it crosses
+		 * ttyinq_block boundaries, because multiple reads could
+		 * then make this code read beyond the newline.
+		 *
+		 * This is why we limit the read to:
+		 * - The size the user has requested
+		 * - The blocksize (done in tty_inq.c)
+		 * - The amount of bytes until the newline
+		 *
+		 * This causes the line length to be recalculated after
+		 * each block has been copied to userspace. This will
+		 * cause the TTY layer to return data in chunks using
+		 * the blocksize (except the first and last blocks).
+		 */
+		clen = ttyinq_findchar(&tp->t_inq, breakc, uio->uio_resid,
+		    &lastc);
+
+		/* No more data. */
+		if (clen == 0) {
+			if (tp->t_flags & TF_ZOMBIE)
+				return (0);
+			else if (ioflag & IO_NDELAY)
+				return (EWOULDBLOCK);
+
+			error = tty_wait(tp, &tp->t_inwait);
+			if (error)
+				return (error);
+			continue;
+		}
+
+		/* Don't send the EOF char back to userspace. */
+		if (CMP_CC(VEOF, lastc))
+			flen = 1;
+
+		MPASS(flen <= clen);
+
+		/* Read and throw away the EOF character. */
+		error = ttyinq_read_uio(&tp->t_inq, tp, uio, clen, flen);
+		if (error)
+			return (error);
+
+	} while (uio->uio_resid > 0 && lastc == _POSIX_VDISABLE);
+
+	return (0);
+}
+
+static int
+ttydisc_read_raw_no_timer(struct tty *tp, struct uio *uio, int ioflag)
+{
+	size_t vmin = tp->t_termios.c_cc[VMIN];
+	ssize_t oresid = uio->uio_resid;
+	int error;
+
+	MPASS(tp->t_termios.c_cc[VTIME] == 0);
+
+	/*
+	 * This routine implements the easy cases of read()s while in
+	 * non-canonical mode, namely case B and D, where we don't have
+	 * any timers at all.
+	 */
+
+	for (;;) {
+		error = tty_wait_background(tp, curthread, SIGTTIN);
+		if (error)
+			return (error);
+
+		error = ttyinq_read_uio(&tp->t_inq, tp, uio,
+		    uio->uio_resid, 0);
+		if (error)
+			return (error);
+		if (uio->uio_resid == 0 || (oresid - uio->uio_resid) >= vmin)
+			return (0);
+
+		/* We have to wait for more. */
+		if (tp->t_flags & TF_ZOMBIE)
+			return (0);
+		else if (ioflag & IO_NDELAY)
+			return (EWOULDBLOCK);
+
+		error = tty_wait(tp, &tp->t_inwait);
+		if (error)
+			return (error);
+	}
+}
+
+static int
+ttydisc_read_raw_read_timer(struct tty *tp, struct uio *uio, int ioflag,
+    int oresid)
+{
+	size_t vmin = MAX(tp->t_termios.c_cc[VMIN], 1);
+	unsigned int vtime = tp->t_termios.c_cc[VTIME];
+	struct timeval end, now, left;
+	int error, hz;
+
+	MPASS(tp->t_termios.c_cc[VTIME] != 0);
+
+	/* Determine when the read should be expired. */
+	end.tv_sec = vtime / 10;
+	end.tv_usec = (vtime % 10) * 100000;
+	getmicrotime(&now);
+	timevaladd(&end, &now);
+
+	for (;;) {
+		error = tty_wait_background(tp, curthread, SIGTTIN);
+		if (error)
+			return (error);
+
+		error = ttyinq_read_uio(&tp->t_inq, tp, uio,
+		    uio->uio_resid, 0);
+		if (error)
+			return (error);
+		if (uio->uio_resid == 0 || (oresid - uio->uio_resid) >= vmin)
+			return (0);
+
+		/* Calculate how long we should wait. */
+		getmicrotime(&now);
+		if (timevalcmp(&now, &end, >))
+			return (0);
+		left = end;
+		timevalsub(&left, &now);
+		hz = tvtohz(&left);
+
+		/*
+		 * We have to wait for more. If the timer expires, we
+		 * should return a 0-byte read.
+		 */
+		if (tp->t_flags & TF_ZOMBIE)
+			return (0);
+		else if (ioflag & IO_NDELAY)
+			return (EWOULDBLOCK);
+
+		error = tty_timedwait(tp, &tp->t_inwait, hz);
+		if (error)
+			return (error == EWOULDBLOCK ? 0 : error);
+	}
+
+	return (0);
+}
+
+static int
+ttydisc_read_raw_interbyte_timer(struct tty *tp, struct uio *uio, int ioflag)
+{
+	size_t vmin = tp->t_termios.c_cc[VMIN];
+	ssize_t oresid = uio->uio_resid;
+	int error;
+
+	MPASS(tp->t_termios.c_cc[VMIN] != 0);
+	MPASS(tp->t_termios.c_cc[VTIME] != 0);
+
+	/*
+	 * When using the interbyte timer, the timer should be started
+	 * after the first byte has been received. We just call into the
+	 * generic read timer code after we've received the first byte.
+	 */
+
+	for (;;) {
+		error = tty_wait_background(tp, curthread, SIGTTIN);
+		if (error)
+			return (error);
+
+		error = ttyinq_read_uio(&tp->t_inq, tp, uio,
+		    uio->uio_resid, 0);
+		if (error)
+			return (error);
+		if (uio->uio_resid == 0 || (oresid - uio->uio_resid) >= vmin)
+			return (0);
+
+		/*
+		 * Not enough data, but we did receive some, which means
+		 * we'll now start using the interbyte timer.
+		 */
+		if (oresid != uio->uio_resid)
+			break;
+
+		/* We have to wait for more. */
+		if (tp->t_flags & TF_ZOMBIE)
+			return (0);
+		else if (ioflag & IO_NDELAY)
+			return (EWOULDBLOCK);
+
+		error = tty_wait(tp, &tp->t_inwait);
+		if (error)
+			return (error);
+	}
+
+	return ttydisc_read_raw_read_timer(tp, uio, ioflag, oresid);
+}
+
+int
+ttydisc_read(struct tty *tp, struct uio *uio, int ioflag)
+{
+	int error;
+
+	tty_lock_assert(tp, MA_OWNED);
+
+	if (uio->uio_resid == 0)
+		return (0);
+
+	if (CMP_FLAG(l, ICANON))
+		error = ttydisc_read_canonical(tp, uio, ioflag);
+	else if (tp->t_termios.c_cc[VTIME] == 0)
+		error = ttydisc_read_raw_no_timer(tp, uio, ioflag);
+	else if (tp->t_termios.c_cc[VMIN] == 0)
+		error = ttydisc_read_raw_read_timer(tp, uio, ioflag,
+		    uio->uio_resid);
+	else
+		error = ttydisc_read_raw_interbyte_timer(tp, uio, ioflag);
+
+	if (ttyinq_bytesleft(&tp->t_inq) >= tp->t_inlow ||
+	    ttyinq_bytescanonicalized(&tp->t_inq) == 0) {
+		/* Unset the input watermark when we've got enough space. */
+		tty_hiwat_in_unblock(tp);
+	}
+
+	return (error);
+}
+
+static __inline unsigned int
+ttydisc_findchar(const char *obstart, unsigned int oblen)
+{
+	const char *c = obstart;
+
+	while (oblen--) {
+		if (CTL_VALID(*c))
+			break;
+		c++;
+	}
+
+	return (c - obstart);
+}
+
+static int
+ttydisc_write_oproc(struct tty *tp, char c)
+{
+	unsigned int scnt, error;
+
+	MPASS(CMP_FLAG(o, OPOST));
+	MPASS(CTL_VALID(c));
+
+#define PRINT_NORMAL() ttyoutq_write_nofrag(&tp->t_outq, &c, 1)
+	switch (c) {
+	case CEOF:
+		/* End-of-text dropping. */
+		if (CMP_FLAG(o, ONOEOT))
+			return (0);
+		return PRINT_NORMAL();
+
+	case CERASE2:
+		/* Handle backspace to fix tab expansion. */
+		if (PRINT_NORMAL() != 0)
+			return (-1);
+		if (tp->t_column > 0)
+			tp->t_column--;
+		return (0);
+
+	case CTAB:
+		/* Tab expansion. */
+		scnt = 8 - (tp->t_column & 7);
+		if (CMP_FLAG(o, TAB3)) {
+			error = ttyoutq_write_nofrag(&tp->t_outq,
+			    "        ", scnt);
+		} else {
+			error = PRINT_NORMAL();
+		}
+		if (error)
+			return (-1);
+
+		tp->t_column += scnt;
+		MPASS((tp->t_column % 8) == 0);
+		return (0);
+
+	case CNL:
+		/* Newline conversion. */
+		if (CMP_FLAG(o, ONLCR)) {
+			/* Convert \n to \r\n. */
+			error = ttyoutq_write_nofrag(&tp->t_outq, "\r\n", 2);
+		} else {
+			error = PRINT_NORMAL();
+		}
+		if (error)
+			return (-1);
+
+		if (CMP_FLAG(o, ONLCR|ONLRET)) {
+			tp->t_column = tp->t_writepos = 0;
+			ttyinq_reprintpos_set(&tp->t_inq);
+		}
+		return (0);
+
+	case CCR:
+		/* Carriage return to newline conversion. */
+		if (CMP_FLAG(o, OCRNL))
+			c = CNL;
+		/* Omit carriage returns on column 0. */
+		if (CMP_FLAG(o, ONOCR) && tp->t_column == 0)
+			return (0);
+		if (PRINT_NORMAL() != 0)
+			return (-1);
+
+		tp->t_column = tp->t_writepos = 0;
+		ttyinq_reprintpos_set(&tp->t_inq);
+		return (0);
+	}
+
+	/*
+	 * Invisible control character. Print it, but don't
+	 * increase the column count.
+	 */
+	return PRINT_NORMAL();
+#undef PRINT_NORMAL
+}
+
+/*
+ * Just like the old TTY implementation, we need to copy data in chunks
+ * into a temporary buffer. One of the reasons why we need to do this,
+ * is because output processing (only TAB3 though) may allow the buffer
+ * to grow eight times.
+ */
+int
+ttydisc_write(struct tty *tp, struct uio *uio, int ioflag)
+{
+	char ob[TTY_STACKBUF];
+	char *obstart;
+	int error = 0;
+	unsigned int oblen = 0;
+
+	tty_lock_assert(tp, MA_OWNED);
+
+	if (tp->t_flags & TF_ZOMBIE)
+		return (EIO);
+
+	/*
+	 * We don't need to check whether the process is the foreground
+	 * process group or if we have a carrier. This is already done
+	 * in ttydev_write().
+	 */
+
+	while (uio->uio_resid > 0) {
+		unsigned int nlen;
+
+		MPASS(oblen == 0);
+
+		/* Step 1: read data. */
+		obstart = ob;
+		nlen = MIN(uio->uio_resid, sizeof ob);
+		tty_unlock(tp);
+		error = uiomove(ob, nlen, uio);
+		tty_lock(tp);
+		if (error != 0)
+			break;
+		oblen = nlen;
+
+		if (tty_gone(tp)) {
+			error = ENXIO;
+			break;
+		}
+
+		MPASS(oblen > 0);
+
+		/* Step 2: process data. */
+		do {
+			unsigned int plen, wlen;
+
+			/* Search for special characters for post processing. */
+			if (CMP_FLAG(o, OPOST)) {
+				plen = ttydisc_findchar(obstart, oblen);
+			} else {
+				plen = oblen;
+			}
+
+			if (plen == 0) {
+				/*
+				 * We're going to process a character
+				 * that needs processing
+				 */
+				if (ttydisc_write_oproc(tp, *obstart) == 0) {
+					obstart++;
+					oblen--;
+
+					tp->t_writepos = tp->t_column;
+					ttyinq_reprintpos_set(&tp->t_inq);
+					continue;
+				}
+			} else {
+				/* We're going to write regular data. */
+				wlen = ttyoutq_write(&tp->t_outq, obstart, plen);
+				obstart += wlen;
+				oblen -= wlen;
+				tp->t_column += wlen;
+
+				tp->t_writepos = tp->t_column;
+				ttyinq_reprintpos_set(&tp->t_inq);
+
+				if (wlen == plen)
+					continue;
+			}
+
+			/* Watermark reached. Try to sleep. */
+			tp->t_flags |= TF_HIWAT_OUT;
+
+			if (ioflag & IO_NDELAY) {
+				error = EWOULDBLOCK;
+				goto done;
+			}
+
+			/*
+			 * The driver may write back the data
+			 * synchronously. Be sure to check the high
+			 * water mark before going to sleep.
+			 */
+			ttydevsw_outwakeup(tp);
+			if ((tp->t_flags & TF_HIWAT_OUT) == 0)
+				continue;
+
+			error = tty_wait(tp, &tp->t_outwait);
+			if (error)
+				goto done;
+
+			if (tp->t_flags & TF_ZOMBIE) {
+				error = EIO;
+				goto done;
+			}
+		} while (oblen > 0);
+	}
+
+done:
+	if (!tty_gone(tp))
+		ttydevsw_outwakeup(tp);
+
+	/*
+	 * Add the amount of bytes that we didn't process back to the
+	 * uio counters. We need to do this to make sure write() doesn't
+	 * count the bytes we didn't store in the queue.
+	 */
+	uio->uio_resid += oblen;
+	return (error);
+}
+
+void
+ttydisc_optimize(struct tty *tp)
+{
+	tty_lock_assert(tp, MA_OWNED);
+
+	if (ttyhook_hashook(tp, rint_bypass)) {
+		tp->t_flags |= TF_BYPASS;
+	} else if (ttyhook_hashook(tp, rint)) {
+		tp->t_flags &= ~TF_BYPASS;
+	} else if (!CMP_FLAG(i, ICRNL|IGNCR|IMAXBEL|INLCR|ISTRIP|IXON) &&
+	    (!CMP_FLAG(i, BRKINT) || CMP_FLAG(i, IGNBRK)) &&
+	    (!CMP_FLAG(i, PARMRK) ||
+		CMP_FLAG(i, IGNPAR|IGNBRK) == (IGNPAR|IGNBRK)) &&
+	    !CMP_FLAG(l, ECHO|ICANON|IEXTEN|ISIG|PENDIN)) {
+		tp->t_flags |= TF_BYPASS;
+	} else {
+		tp->t_flags &= ~TF_BYPASS;
+	}
+}
+
+void
+ttydisc_modem(struct tty *tp, int open)
+{
+
+	tty_lock_assert(tp, MA_OWNED);
+
+	if (open)
+		cv_broadcast(&tp->t_dcdwait);
+
+	/*
+	 * Ignore modem status lines when CLOCAL is turned on, but don't
+	 * enter the zombie state when the TTY isn't opened, because
+	 * that would cause the TTY to be in zombie state after being
+	 * opened.
+	 */
+	if (!tty_opened(tp) || CMP_FLAG(c, CLOCAL))
+		return;
+
+	if (open == 0) {
+		/*
+		 * Lost carrier.
+		 */
+		tp->t_flags |= TF_ZOMBIE;
+
+		tty_signal_sessleader(tp, SIGHUP);
+		tty_flush(tp, FREAD|FWRITE);
+	} else {
+		/*
+		 * Carrier is back again.
+		 */
+
+		/* XXX: what should we do here? */
+	}
+}
+
+static int
+ttydisc_echo_force(struct tty *tp, char c, int quote)
+{
+
+	if (CMP_FLAG(o, OPOST) && CTL_ECHO(c, quote)) {
+		/*
+		 * Only perform postprocessing when OPOST is turned on
+		 * and the character is an unquoted BS/TB/NL/CR.
+		 */
+		return ttydisc_write_oproc(tp, c);
+	} else if (CMP_FLAG(l, ECHOCTL) && CTL_PRINT(c, quote)) {
+		/*
+		 * Only use ^X notation when ECHOCTL is turned on and
+		 * we've got an quoted control character.
+		 *
+		 * Print backspaces when echoing an end-of-file.
+		 */
+		char ob[4] = "^?\b\b";
+
+		/* Print ^X notation. */
+		if (c != 0x7f)
+			ob[1] = c + 'A' - 1;
+
+		if (!quote && CMP_CC(VEOF, c)) {
+			return ttyoutq_write_nofrag(&tp->t_outq, ob, 4);
+		} else {
+			tp->t_column += 2;
+			return ttyoutq_write_nofrag(&tp->t_outq, ob, 2);
+		}
+	} else {
+		/* Can just be printed. */
+		tp->t_column++;
+		return ttyoutq_write_nofrag(&tp->t_outq, &c, 1);
+	}
+}
+
+static int
+ttydisc_echo(struct tty *tp, char c, int quote)
+{
+
+	/*
+	 * Only echo characters when ECHO is turned on, or ECHONL when
+	 * the character is an unquoted newline.
+	 */
+	if (!CMP_FLAG(l, ECHO) &&
+	    (!CMP_FLAG(l, ECHONL) || c != CNL || quote))
+		return (0);
+
+	return ttydisc_echo_force(tp, c, quote);
+}
+
+static void
+ttydisc_reprint_char(void *d, char c, int quote)
+{
+	struct tty *tp = d;
+
+	ttydisc_echo(tp, c, quote);
+}
+
+static void
+ttydisc_reprint(struct tty *tp)
+{
+	cc_t c;
+
+	/* Print  ^R\n, followed by the line. */
+	c = tp->t_termios.c_cc[VREPRINT];
+	if (c != _POSIX_VDISABLE)
+		ttydisc_echo(tp, c, 0);
+	ttydisc_echo(tp, CNL, 0);
+	ttyinq_reprintpos_reset(&tp->t_inq);
+
+	ttyinq_line_iterate_from_linestart(&tp->t_inq, ttydisc_reprint_char, tp);
+}
+
+struct ttydisc_recalc_length {
+	struct tty *tp;
+	unsigned int curlen;
+};
+
+static void
+ttydisc_recalc_charlength(void *d, char c, int quote)
+{
+	struct ttydisc_recalc_length *data = d;
+	struct tty *tp = data->tp;
+
+	if (CTL_PRINT(c, quote)) {
+		if (CMP_FLAG(l, ECHOCTL))
+			data->curlen += 2;
+	} else if (c == CTAB) {
+		data->curlen += 8 - (data->curlen & 7);
+	} else {
+		data->curlen++;
+	}
+}
+
+static unsigned int
+ttydisc_recalc_linelength(struct tty *tp)
+{
+	struct ttydisc_recalc_length data = { tp, tp->t_writepos };
+
+	ttyinq_line_iterate_from_reprintpos(&tp->t_inq,
+	    ttydisc_recalc_charlength, &data);
+	return (data.curlen);
+}
+
+static int
+ttydisc_rubchar(struct tty *tp)
+{
+	char c;
+	int quote;
+	unsigned int prevpos, tablen;
+
+	if (ttyinq_peekchar(&tp->t_inq, &c, &quote) != 0)
+		return (-1);
+	ttyinq_unputchar(&tp->t_inq);
+
+	if (CMP_FLAG(l, ECHO)) {
+		/*
+		 * Remove the character from the screen. This is even
+		 * safe for characters that span multiple characters
+		 * (tabs, quoted, etc).
+		 */
+		if (tp->t_writepos >= tp->t_column) {
+			/* Retype the sentence. */
+			ttydisc_reprint(tp);
+		} else if (CMP_FLAG(l, ECHOE)) {
+			if (CTL_PRINT(c, quote)) {
+				/* Remove ^X formatted chars. */
+				if (CMP_FLAG(l, ECHOCTL)) {
+					tp->t_column -= 2;
+					ttyoutq_write_nofrag(&tp->t_outq,
+					    "\b\b  \b\b", 6);
+				}
+			} else if (c == ' ') {
+				/* Space character needs no rubbing. */
+				tp->t_column -= 1;
+				ttyoutq_write_nofrag(&tp->t_outq, "\b", 1);
+			} else if (c == CTAB) {
+				/*
+				 * Making backspace work with tabs is
+				 * quite hard. Recalculate the length of
+				 * this character and remove it.
+				 *
+				 * Because terminal settings could be
+				 * changed while the line is being
+				 * inserted, the calculations don't have
+				 * to be correct. Make sure we keep the
+				 * tab length within proper bounds.
+				 */
+				prevpos = ttydisc_recalc_linelength(tp);
+				if (prevpos >= tp->t_column)
+					tablen = 1;
+				else
+					tablen = tp->t_column - prevpos;
+				if (tablen > 8)
+					tablen = 8;
+
+				tp->t_column = prevpos;
+				ttyoutq_write_nofrag(&tp->t_outq,
+				    "\b\b\b\b\b\b\b\b", tablen);
+				return (0);
+			} else {
+				/*
+				 * Remove a regular character by
+				 * punching a space over it.
+				 */
+				tp->t_column -= 1;
+				ttyoutq_write_nofrag(&tp->t_outq, "\b \b", 3);
+			}
+		} else {
+			/* Don't print spaces. */
+			ttydisc_echo(tp, tp->t_termios.c_cc[VERASE], 0);
+		}
+	}
+
+	return (0);
+}
+
+static void
+ttydisc_rubword(struct tty *tp)
+{
+	char c;
+	int quote, alnum;
+
+	/* Strip whitespace first. */
+	for (;;) {
+		if (ttyinq_peekchar(&tp->t_inq, &c, &quote) != 0)
+			return;
+		if (!CTL_WHITE(c))
+			break;
+		ttydisc_rubchar(tp);
+	}
+
+	/*
+	 * Record whether the last character from the previous iteration
+	 * was alphanumeric or not. We need this to implement ALTWERASE.
+	 */
+	alnum = CTL_ALNUM(c);
+	for (;;) {
+		ttydisc_rubchar(tp);
+
+		if (ttyinq_peekchar(&tp->t_inq, &c, &quote) != 0)
+			return;
+		if (CTL_WHITE(c))
+			return;
+		if (CMP_FLAG(l, ALTWERASE) && CTL_ALNUM(c) != alnum)
+			return;
+	}
+}
+
+int
+ttydisc_rint(struct tty *tp, char c, int flags)
+{
+	int signal, quote = 0;
+	char ob[3] = { 0xff, 0x00 };
+	size_t ol;
+
+	tty_lock_assert(tp, MA_OWNED);
+
+	atomic_add_long(&tty_nin, 1);
+
+	if (ttyhook_hashook(tp, rint))
+		return ttyhook_rint(tp, c, flags);
+
+	if (tp->t_flags & TF_BYPASS)
+		goto processed;
+
+	if (flags) {
+		if (flags & TRE_BREAK) {
+			if (CMP_FLAG(i, IGNBRK)) {
+				/* Ignore break characters. */
+				return (0);
+			} else if (CMP_FLAG(i, BRKINT)) {
+				/* Generate SIGINT on break. */
+				tty_flush(tp, FREAD|FWRITE);
+				tty_signal_pgrp(tp, SIGINT);
+				return (0);
+			} else {
+				/* Just print it. */
+				goto parmrk;
+			}
+		} else if (flags & TRE_FRAMING ||
+		    (flags & TRE_PARITY && CMP_FLAG(i, INPCK))) {
+			if (CMP_FLAG(i, IGNPAR)) {
+				/* Ignore bad characters. */
+				return (0);
+			} else {
+				/* Just print it. */
+				goto parmrk;
+			}
+		}
+	}
+
+	/* Allow any character to perform a wakeup. */
+	if (CMP_FLAG(i, IXANY))
+		tp->t_flags &= ~TF_STOPPED;
+
+	/* Remove the top bit. */
+	if (CMP_FLAG(i, ISTRIP))
+		c &= ~0x80;
+
+	/* Skip input processing when we want to print it literally. */
+	if (tp->t_flags & TF_LITERAL) {
+		tp->t_flags &= ~TF_LITERAL;
+		quote = 1;
+		goto processed;
+	}
+
+	/* Special control characters that are implementation dependent. */
+	if (CMP_FLAG(l, IEXTEN)) {
+		/* Accept the next character as literal. */
+		if (CMP_CC(VLNEXT, c)) {
+			if (CMP_FLAG(l, ECHO)) {
+				if (CMP_FLAG(l, ECHOE))
+					ttyoutq_write_nofrag(&tp->t_outq, "^\b", 2);
+				else
+					ttydisc_echo(tp, c, 0);
+			}
+			tp->t_flags |= TF_LITERAL;
+			return (0);
+		}
+	}
+
+	/*
+	 * Handle signal processing.
+	 */
+	if (CMP_FLAG(l, ISIG)) {
+		if (CMP_FLAG(l, ICANON|IEXTEN) == (ICANON|IEXTEN)) {
+			if (CMP_CC(VSTATUS, c)) {
+				tty_signal_pgrp(tp, SIGINFO);
+				return (0);
+			}
+		}
+
+		/*
+		 * When compared to the old implementation, this
+		 * implementation also flushes the output queue. POSIX
+		 * is really brief about this, but does makes us assume
+		 * we have to do so.
+		 */
+		signal = 0;
+		if (CMP_CC(VINTR, c)) {
+			signal = SIGINT;
+		} else if (CMP_CC(VQUIT, c)) {
+			signal = SIGQUIT;
+		} else if (CMP_CC(VSUSP, c)) {
+			signal = SIGTSTP;
+		}
+
+		if (signal != 0) {
+			/*
+			 * Echo the character before signalling the
+			 * processes.
+			 */
+			if (!CMP_FLAG(l, NOFLSH))
+				tty_flush(tp, FREAD|FWRITE);
+			ttydisc_echo(tp, c, 0);
+			tty_signal_pgrp(tp, signal);
+			return (0);
+		}
+	}
+
+	/*
+	 * Handle start/stop characters.
+	 */
+	if (CMP_FLAG(i, IXON)) {
+		if (CMP_CC(VSTOP, c)) {
+			/* Stop it if we aren't stopped yet. */
+			if ((tp->t_flags & TF_STOPPED) == 0) {
+				tp->t_flags |= TF_STOPPED;
+				return (0);
+			}
+			/*
+			 * Fallthrough:
+			 * When VSTART == VSTOP, we should make this key
+			 * toggle it.
+			 */
+			if (!CMP_CC(VSTART, c))
+				return (0);
+		}
+		if (CMP_CC(VSTART, c)) {
+			tp->t_flags &= ~TF_STOPPED;
+			return (0);
+		}
+	}
+
+	/* Conversion of CR and NL. */
+	switch (c) {
+	case CCR:
+		if (CMP_FLAG(i, IGNCR))
+			return (0);
+		if (CMP_FLAG(i, ICRNL))
+			c = CNL;
+		break;
+	case CNL:
+		if (CMP_FLAG(i, INLCR))
+			c = CCR;
+		break;
+	}
+
+	/* Canonical line editing. */
+	if (CMP_FLAG(l, ICANON)) {
+		if (CMP_CC(VERASE, c) || CMP_CC(VERASE2, c)) {
+			ttydisc_rubchar(tp);
+			return (0);
+		} else if (CMP_CC(VKILL, c)) {
+			while (ttydisc_rubchar(tp) == 0);
+			return (0);
+		} else if (CMP_FLAG(l, IEXTEN)) {
+			if (CMP_CC(VWERASE, c)) {
+				ttydisc_rubword(tp);
+				return (0);
+			} else if (CMP_CC(VREPRINT, c)) {
+				ttydisc_reprint(tp);
+				return (0);
+			}
+		}
+	}
+
+processed:
+	if (CMP_FLAG(i, PARMRK) && (unsigned char)c == 0xff) {
+		/* Print 0xff 0xff. */
+		ob[1] = 0xff;
+		ol = 2;
+		quote = 1;
+	} else {
+		ob[0] = c;
+		ol = 1;
+	}
+
+	goto print;
+
+parmrk:
+	if (CMP_FLAG(i, PARMRK)) {
+		/* Prepend 0xff 0x00 0x.. */
+		ob[2] = c;
+		ol = 3;
+		quote = 1;
+	} else {
+		ob[0] = c;
+		ol = 1;
+	}
+
+print:
+	/* See if we can store this on the input queue. */
+	if (ttyinq_write_nofrag(&tp->t_inq, ob, ol, quote) != 0) {
+		if (CMP_FLAG(i, IMAXBEL))
+			ttyoutq_write_nofrag(&tp->t_outq, "\a", 1);
+
+		/*
+		 * Prevent a deadlock here. It may be possible that a
+		 * user has entered so much data, there is no data
+		 * available to read(), but the buffers are full anyway.
+		 *
+		 * Only enter the high watermark if the device driver
+		 * can actually transmit something.
+		 */
+		if (ttyinq_bytescanonicalized(&tp->t_inq) == 0)
+			return (0);
+
+		tty_hiwat_in_block(tp);
+		return (-1);
+	}
+
+	/*
+	 * In raw mode, we canonicalize after receiving a single
+	 * character. Otherwise, we canonicalize when we receive a
+	 * newline, VEOL or VEOF, but only when it isn't quoted.
+	 */
+	if (!CMP_FLAG(l, ICANON) ||
+	    (!quote && (c == CNL || CMP_CC(VEOL, c) || CMP_CC(VEOF, c)))) {
+		ttyinq_canonicalize(&tp->t_inq);
+	}
+
+	ttydisc_echo(tp, c, quote);
+
+	return (0);
+}
+
+size_t
+ttydisc_rint_simple(struct tty *tp, const void *buf, size_t len)
+{
+	const char *cbuf;
+
+	if (ttydisc_can_bypass(tp))
+		return (ttydisc_rint_bypass(tp, buf, len));
+
+	for (cbuf = buf; len-- > 0; cbuf++) {
+		if (ttydisc_rint(tp, *cbuf, 0) != 0)
+			break;
+	}
+
+	return (cbuf - (const char *)buf);
+}
+
+size_t
+ttydisc_rint_bypass(struct tty *tp, const void *buf, size_t len)
+{
+	size_t ret;
+
+	tty_lock_assert(tp, MA_OWNED);
+
+	MPASS(tp->t_flags & TF_BYPASS);
+
+	atomic_add_long(&tty_nin, len);
+
+	if (ttyhook_hashook(tp, rint_bypass))
+		return ttyhook_rint_bypass(tp, buf, len);
+
+	ret = ttyinq_write(&tp->t_inq, buf, len, 0);
+	ttyinq_canonicalize(&tp->t_inq);
+	if (ret < len)
+		tty_hiwat_in_block(tp);
+
+	return (ret);
+}
+
+void
+ttydisc_rint_done(struct tty *tp)
+{
+
+	tty_lock_assert(tp, MA_OWNED);
+
+	if (ttyhook_hashook(tp, rint_done))
+		ttyhook_rint_done(tp);
+
+	/* Wake up readers. */
+	tty_wakeup(tp, FREAD);
+	/* Wake up driver for echo. */
+	ttydevsw_outwakeup(tp);
+}
+
+size_t
+ttydisc_rint_poll(struct tty *tp)
+{
+	size_t l;
+
+	tty_lock_assert(tp, MA_OWNED);
+
+	if (ttyhook_hashook(tp, rint_poll))
+		return ttyhook_rint_poll(tp);
+
+	/*
+	 * XXX: Still allow character input when there's no space in the
+	 * buffers, but we haven't entered the high watermark. This is
+	 * to allow backspace characters to be inserted when in
+	 * canonical mode.
+	 */
+	l = ttyinq_bytesleft(&tp->t_inq);
+	if (l == 0 && (tp->t_flags & TF_HIWAT_IN) == 0)
+		return (1);
+
+	return (l);
+}
+
+static void
+ttydisc_wakeup_watermark(struct tty *tp)
+{
+	size_t c;
+
+	c = ttyoutq_bytesleft(&tp->t_outq);
+	if (tp->t_flags & TF_HIWAT_OUT) {
+		/* Only allow us to run when we're below the watermark. */
+		if (c < tp->t_outlow)
+			return;
+
+		/* Reset the watermark. */
+		tp->t_flags &= ~TF_HIWAT_OUT;
+	} else {
+		/* Only run when we have data at all. */
+		if (c == 0)
+			return;
+	}
+	tty_wakeup(tp, FWRITE);
+}
+
+size_t
+ttydisc_getc(struct tty *tp, void *buf, size_t len)
+{
+
+	tty_lock_assert(tp, MA_OWNED);
+
+	if (tp->t_flags & TF_STOPPED)
+		return (0);
+
+	if (ttyhook_hashook(tp, getc_inject))
+		return ttyhook_getc_inject(tp, buf, len);
+
+	len = ttyoutq_read(&tp->t_outq, buf, len);
+
+	if (ttyhook_hashook(tp, getc_capture))
+		ttyhook_getc_capture(tp, buf, len);
+
+	ttydisc_wakeup_watermark(tp);
+	atomic_add_long(&tty_nout, len);
+
+	return (len);
+}
+
+int
+ttydisc_getc_uio(struct tty *tp, struct uio *uio)
+{
+	int error = 0;
+	ssize_t obytes = uio->uio_resid;
+	size_t len;
+	char buf[TTY_STACKBUF];
+
+	tty_lock_assert(tp, MA_OWNED);
+
+	if (tp->t_flags & TF_STOPPED)
+		return (0);
+
+	/*
+	 * When a TTY hook is attached, we cannot perform unbuffered
+	 * copying to userspace. Just call ttydisc_getc() and
+	 * temporarily store data in a shadow buffer.
+	 */
+	if (ttyhook_hashook(tp, getc_capture) ||
+	    ttyhook_hashook(tp, getc_inject)) {
+		while (uio->uio_resid > 0) {
+			/* Read to shadow buffer. */
+			len = ttydisc_getc(tp, buf,
+			    MIN(uio->uio_resid, sizeof buf));
+			if (len == 0)
+				break;
+
+			/* Copy to userspace. */
+			tty_unlock(tp);
+			error = uiomove(buf, len, uio);
+			tty_lock(tp);
+
+			if (error != 0)
+				break;
+		}
+	} else {
+		error = ttyoutq_read_uio(&tp->t_outq, tp, uio);
+
+		ttydisc_wakeup_watermark(tp);
+		atomic_add_long(&tty_nout, obytes - uio->uio_resid);
+	}
+
+	return (error);
+}
+
+size_t
+ttydisc_getc_poll(struct tty *tp)
+{
+
+	tty_lock_assert(tp, MA_OWNED);
+
+	if (tp->t_flags & TF_STOPPED)
+		return (0);
+
+	if (ttyhook_hashook(tp, getc_poll))
+		return ttyhook_getc_poll(tp);
+
+	return ttyoutq_bytesused(&tp->t_outq);
+}
+
+/*
+ * XXX: not really related to the TTYDISC, but we'd better put
+ * tty_putchar() here, because we need to perform proper output
+ * processing.
+ */
+
+int
+tty_putchar(struct tty *tp, char c)
+{
+	tty_lock_assert(tp, MA_OWNED);
+
+	if (tty_gone(tp))
+		return (-1);
+
+	ttydisc_echo_force(tp, c, 0);
+	tp->t_writepos = tp->t_column;
+	ttyinq_reprintpos_set(&tp->t_inq);
+
+	ttydevsw_outwakeup(tp);
+	return (0);
+}