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, 157 insertions, 0 deletions

diff --git a/sys/sys/ttyqueue.h b/sys/sys/ttyqueue.h
new file mode 100644
index 0000000..3e72fef
--- /dev/null
+++ b/sys/sys/ttyqueue.h
@@ -0,0 +1,157 @@
+/*-
+ * 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_TTYQUEUE_H_
+#define	_SYS_TTYQUEUE_H_
+
+#ifndef _SYS_TTY_H_
+#error "can only be included through <sys/tty.h>"
+#endif /* !_SYS_TTY_H_ */
+
+struct tty;
+struct ttyinq_block;
+struct ttyoutq_block;
+struct uio;
+
+/* Data input queue. */
+struct ttyinq {
+	TAILQ_HEAD(ttyinq_bhead, ttyinq_block) ti_list;
+	struct ttyinq_block		*ti_startblock;
+	struct ttyinq_block		*ti_reprintblock;
+	struct ttyinq_block		*ti_lastblock;
+	unsigned int			ti_begin;
+	unsigned int			ti_linestart;
+	unsigned int			ti_reprint;
+	unsigned int			ti_end;
+	unsigned int			ti_nblocks;
+};
+#define TTYINQ_DATASIZE 128
+
+/* Data output queue. */
+struct ttyoutq {
+	STAILQ_HEAD(, ttyoutq_block)	to_list;
+	struct ttyoutq_block		*to_lastblock;
+	unsigned int			to_begin;
+	unsigned int			to_end;
+	unsigned int			to_nblocks;
+};
+#define TTYOUTQ_DATASIZE (256 - sizeof(STAILQ_ENTRY(ttyoutq_block)))
+
+#ifdef _KERNEL
+/* Input queue handling routines. */
+void	ttyinq_setsize(struct ttyinq *, struct tty *, size_t);
+int	ttyinq_read_uio(struct ttyinq *, struct tty *, struct uio *,
+    size_t, size_t);
+size_t	ttyinq_write(struct ttyinq *, const void *, size_t, int);
+int	ttyinq_write_nofrag(struct ttyinq *, const void *, size_t, int);
+void	ttyinq_canonicalize(struct ttyinq *);
+size_t	ttyinq_findchar(struct ttyinq *, const char *, size_t, char *);
+void	ttyinq_flush(struct ttyinq *);
+int	ttyinq_peekchar(struct ttyinq *, char *, int *);
+void	ttyinq_unputchar(struct ttyinq *);
+void	ttyinq_reprintpos_set(struct ttyinq *);
+void	ttyinq_reprintpos_reset(struct ttyinq *);
+
+static __inline size_t
+ttyinq_getsize(struct ttyinq *ti)
+{
+	return (ti->ti_nblocks * TTYINQ_DATASIZE);
+}
+
+static __inline size_t
+ttyinq_bytesleft(struct ttyinq *ti)
+{
+	size_t len;
+
+	/* Make sure the usage never exceeds the length. */
+	len = ti->ti_nblocks * TTYINQ_DATASIZE;
+	MPASS(len >= ti->ti_end);
+
+	return (len - ti->ti_end);
+}
+
+static __inline size_t
+ttyinq_bytescanonicalized(struct ttyinq *ti)
+{
+	MPASS(ti->ti_begin <= ti->ti_linestart);
+
+	return (ti->ti_linestart - ti->ti_begin);
+}
+
+static __inline size_t
+ttyinq_bytesline(struct ttyinq *ti)
+{
+	MPASS(ti->ti_linestart <= ti->ti_end);
+
+	return (ti->ti_end - ti->ti_linestart);
+}
+
+/* Input buffer iteration. */
+typedef void ttyinq_line_iterator_t(void *, char, int);
+void	ttyinq_line_iterate_from_linestart(struct ttyinq *,
+    ttyinq_line_iterator_t *, void *);
+void	ttyinq_line_iterate_from_reprintpos(struct ttyinq *,
+    ttyinq_line_iterator_t *, void *);
+
+/* Output queue handling routines. */
+void	ttyoutq_flush(struct ttyoutq *);
+void	ttyoutq_setsize(struct ttyoutq *, struct tty *, size_t);
+size_t	ttyoutq_read(struct ttyoutq *, void *, size_t);
+int	ttyoutq_read_uio(struct ttyoutq *, struct tty *, struct uio *);
+size_t	ttyoutq_write(struct ttyoutq *, const void *, size_t);
+int	ttyoutq_write_nofrag(struct ttyoutq *, const void *, size_t);
+
+static __inline size_t
+ttyoutq_getsize(struct ttyoutq *to)
+{
+	return (to->to_nblocks * TTYOUTQ_DATASIZE);
+}
+
+static __inline size_t
+ttyoutq_bytesleft(struct ttyoutq *to)
+{
+	size_t len;
+
+	/* Make sure the usage never exceeds the length. */
+	len = to->to_nblocks * TTYOUTQ_DATASIZE;
+	MPASS(len >= to->to_end);
+
+	return (len - to->to_end);
+}
+
+static __inline size_t
+ttyoutq_bytesused(struct ttyoutq *to)
+{
+	return (to->to_end - to->to_begin);
+}
+#endif /* _KERNEL */
+
+#endif /* !_SYS_TTYQUEUE_H_ */