Integrate the new MPSAFE TTY layer to the FreeBSD operating system.

The last half year I've been working on a replacement TTY layer for the
FreeBSD kernel. The new TTY layer was designed to improve the following:

- Improved driver model:

  The old TTY layer has a driver model that is not abstract enough to
  make it friendly to use. A good example is the output path, where the
  device drivers directly access the output buffers. This means that an
  in-kernel PPP implementation must always convert network buffers into
  TTY buffers.

  If a PPP implementation would be built on top of the new TTY layer
  (still needs a hooks layer, though), it would allow the PPP
  implementation to directly hand the data to the TTY driver.

- Improved hotplugging:

  With the old TTY layer, it isn't entirely safe to destroy TTY's from
  the system. This implementation has a two-step destructing design,
  where the driver first abandons the TTY. After all threads have left
  the TTY, the TTY layer calls a routine in the driver, which can be
  used to free resources (unit numbers, etc).

  The pts(4) driver also implements this feature, which means
  posix_openpt() will now return PTY's that are created on the fly.

- Improved performance:

  One of the major improvements is the per-TTY mutex, which is expected
  to improve scalability when compared to the old Giant locking.
  Another change is the unbuffered copying to userspace, which is both
  used on TTY device nodes and PTY masters.

Upgrading should be quite straightforward. Unlike previous versions,
existing kernel configuration files do not need to be changed, except
when they reference device drivers that are listed in UPDATING.

Obtained from:		//depot/projects/mpsafetty/...
Approved by:		philip (ex-mentor)
Discussed:		on the lists, at BSDCan, at the DevSummit
Sponsored by:		Snow B.V., the Netherlands
dcons(4) fixed by:	kan

1 files changed, 158 insertions, 0 deletions

diff --git a/sys/sys/ttydevsw.h b/sys/sys/ttydevsw.h
new file mode 100644
index 000000000000..a4f5afbbc572
--- /dev/null
+++ b/sys/sys/ttydevsw.h
@@ -0,0 +1,158 @@
+/*-
+ * 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.
+ *
+ * $FreeBSD$
+ */
+
+#ifndef _SYS_TTYDEVSW_H_
+#define	_SYS_TTYDEVSW_H_
+
+#ifndef _SYS_TTY_H_
+#error "can only be included through <sys/tty.h>"
+#endif /* !_SYS_TTY_H_ */
+
+/*
+ * Driver routines that are called from the line discipline to adjust
+ * hardware parameters and such.
+ */
+typedef int tsw_open_t(struct tty *);
+typedef void tsw_close_t(struct tty *);
+typedef void tsw_outwakeup_t(struct tty *);
+typedef void tsw_inwakeup_t(struct tty *);
+typedef int tsw_ioctl_t(struct tty *, u_long, caddr_t, struct thread *);
+typedef int tsw_param_t(struct tty *, struct termios *);
+typedef int tsw_modem_t(struct tty *, int, int);
+typedef int tsw_mmap_t(struct tty *, vm_offset_t, vm_paddr_t *, int);
+typedef void tsw_free_t(void *);
+
+struct ttydevsw {
+	unsigned int	tsw_flags;	/* Default TTY flags. */
+
+	tsw_open_t	*tsw_open;	/* Device opening. */
+	tsw_close_t	*tsw_close;	/* Device closure. */
+
+	tsw_outwakeup_t	*tsw_outwakeup;	/* Output available. */
+	tsw_inwakeup_t	*tsw_inwakeup;	/* Input can be stored again. */
+
+	tsw_ioctl_t	*tsw_ioctl;	/* ioctl() hooks. */
+	tsw_param_t	*tsw_param;	/* TIOCSETA device parameter setting. */
+	tsw_modem_t	*tsw_modem;	/* Modem sigon/sigoff. */
+
+	tsw_mmap_t	*tsw_mmap;	/* mmap() hooks. */
+
+	tsw_free_t	*tsw_free;	/* Destructor. */
+};
+
+static __inline int
+ttydevsw_open(struct tty *tp)
+{
+	tty_lock_assert(tp, MA_OWNED);
+	MPASS(!tty_gone(tp));
+
+	return tp->t_devsw->tsw_open(tp);
+}
+
+static __inline void
+ttydevsw_close(struct tty *tp)
+{
+	tty_lock_assert(tp, MA_OWNED);
+	MPASS(!tty_gone(tp));
+
+	tp->t_devsw->tsw_close(tp);
+}
+
+static __inline void
+ttydevsw_outwakeup(struct tty *tp)
+{
+	tty_lock_assert(tp, MA_OWNED);
+	MPASS(!tty_gone(tp));
+
+	/* Prevent spurious wakeups. */
+	if (tp->t_flags & TF_STOPPED)
+		return;
+	if (ttyoutq_bytesused(&tp->t_outq) == 0)
+		return;
+
+	tp->t_devsw->tsw_outwakeup(tp);
+}
+
+static __inline void
+ttydevsw_inwakeup(struct tty *tp)
+{
+	tty_lock_assert(tp, MA_OWNED);
+	MPASS(!tty_gone(tp));
+
+	/* Prevent spurious wakeups. */
+	if (tp->t_flags & TF_HIWAT_IN)
+		return;
+
+	tp->t_devsw->tsw_inwakeup(tp);
+}
+
+static __inline int
+ttydevsw_ioctl(struct tty *tp, u_long cmd, caddr_t data, struct thread *td)
+{
+	tty_lock_assert(tp, MA_OWNED);
+	MPASS(!tty_gone(tp));
+
+	return tp->t_devsw->tsw_ioctl(tp, cmd, data, td);
+}
+
+static __inline int
+ttydevsw_param(struct tty *tp, struct termios *t)
+{
+	MPASS(!tty_gone(tp));
+
+	return tp->t_devsw->tsw_param(tp, t);
+}
+
+static __inline int
+ttydevsw_modem(struct tty *tp, int sigon, int sigoff)
+{
+	MPASS(!tty_gone(tp));
+
+	return tp->t_devsw->tsw_modem(tp, sigon, sigoff);
+}
+
+static __inline int
+ttydevsw_mmap(struct tty *tp, vm_offset_t offset, vm_paddr_t *paddr, int nprot)
+{
+	MPASS(!tty_gone(tp));
+
+	return tp->t_devsw->tsw_mmap(tp, offset, paddr, nprot);
+}
+
+static __inline void
+ttydevsw_free(struct tty *tp)
+{
+	MPASS(tty_gone(tp));
+
+	tp->t_devsw->tsw_free(tty_softc(tp));
+}
+
+#endif /* !_SYS_TTYDEVSW_H_ */