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, 105 insertions, 0 deletions

diff --git a/sys/sys/ttydisc.h b/sys/sys/ttydisc.h
new file mode 100644
index 0000000..dd170e6
--- /dev/null
+++ b/sys/sys/ttydisc.h
@@ -0,0 +1,105 @@
+/*-
+ * 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_TTYDISC_H_
+#define	_SYS_TTYDISC_H_
+
+#ifndef _SYS_TTY_H_
+#error "can only be included through <sys/tty.h>"
+#endif /* !_SYS_TTY_H_ */
+
+struct cv;
+struct thread;
+struct tty;
+struct uio;
+
+/* Top half routines. */
+void	ttydisc_open(struct tty *);
+void	ttydisc_close(struct tty *);
+int	ttydisc_read(struct tty *, struct uio *, int);
+int	ttydisc_write(struct tty *, struct uio *, int);
+void	ttydisc_optimize(struct tty *);
+
+/* Bottom half routines. */
+void	ttydisc_modem(struct tty *, int);
+#define ttydisc_can_bypass(tp) ((tp)->t_flags & TF_BYPASS)
+int	ttydisc_rint(struct tty *, char, int);
+size_t	ttydisc_rint_bypass(struct tty *, char *, size_t);
+void	ttydisc_rint_done(struct tty *);
+size_t	ttydisc_getc(struct tty *, void *buf, size_t);
+int	ttydisc_getc_uio(struct tty *, struct uio *);
+
+/* Error codes for ttydisc_rint(). */
+#define	TRE_FRAMING	0x01
+#define	TRE_PARITY	0x02
+#define	TRE_OVERRUN	0x04
+#define	TRE_BREAK	0x08
+
+static __inline size_t
+ttydisc_read_poll(struct tty *tp)
+{
+
+	tty_lock_assert(tp, MA_OWNED);
+
+	return ttyinq_bytescanonicalized(&tp->t_inq);
+}
+
+static __inline size_t
+ttydisc_write_poll(struct tty *tp)
+{
+
+	tty_lock_assert(tp, MA_OWNED);
+
+	return ttyoutq_bytesleft(&tp->t_outq);
+}
+
+static __inline size_t
+ttydisc_rint_poll(struct tty *tp)
+{
+
+	tty_lock_assert(tp, MA_OWNED);
+
+	return ttyinq_bytesleft(&tp->t_inq);
+}
+
+static __inline size_t
+ttydisc_getc_poll(struct tty *tp)
+{
+
+	tty_lock_assert(tp, MA_OWNED);
+
+	if (tp->t_flags & TF_STOPPED)
+		return (0);
+
+	return ttyoutq_bytesused(&tp->t_outq);
+}
+
+#endif /* !_SYS_TTYDISC_H_ */