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

2 files changed, 50 insertions, 114 deletions

diff --git a/sys/sun4v/conf/GENERIC b/sys/sun4v/conf/GENERIC
index 4e93a06..1a3f695 100644
--- a/sys/sun4v/conf/GENERIC
+++ b/sys/sun4v/conf/GENERIC
@@ -170,7 +170,7 @@ device		loop		# Network loopback
 device		random		# Entropy device
 device		ether		# Ethernet support
 device		tun		# Packet tunnel.
-device		pty		# Pseudo-ttys (telnet etc)
+device		pty		# BSD-style compatibility pseudo ttys
 device		md		# Memory "disks"
 device		gif		# IPv6 and IPv4 tunneling
 device		faith		# IPv6-to-IPv4 relaying (translation)
diff --git a/sys/sun4v/sun4v/hvcons.c b/sys/sun4v/sun4v/hvcons.c
index 0217a85..314d15c 100644
--- a/sys/sun4v/sun4v/hvcons.c
+++ b/sys/sun4v/sun4v/hvcons.c
@@ -53,16 +53,14 @@ __FBSDID("$FreeBSD$");
 
 #define HVCN_POLL_FREQ 10
 
-
-static d_open_t  hvcn_open;
-static d_close_t hvcn_close;
-
-static struct cdevsw hvcn_cdevsw = {
-	.d_version =	D_VERSION,
-	.d_open =	hvcn_open,
-	.d_close =	hvcn_close,
-	.d_name =	"hvcn",
-	.d_flags =	D_TTY | D_NEEDGIANT,
+static tsw_open_t	hvcn_open;
+static tsw_outwakeup_t	hvcn_outwakeup;
+static tsw_close_t	hvcn_close;
+
+static struct ttydevsw hvcn_class = {
+	.tsw_open	= hvcn_open,
+	.tsw_outwakeup	= hvcn_outwakeup,
+	.tsw_close	= hvcn_close,
 };
 
 #define PCBURST 16
@@ -81,9 +79,6 @@ static struct callout_handle	hvcn_timeouthandle
 static int			alt_break_state;
 #endif
 
-static void	hvcn_tty_start(struct tty *);
-static int	hvcn_tty_param(struct tty *, struct termios *);
-static void	hvcn_tty_stop(struct tty *, int);
 static void     hvcn_timeout(void *);
 
 static cn_probe_t	hvcn_cnprobe;
@@ -113,67 +108,27 @@ hv_cnputs(char *p)
 }
 
 static int
-hvcn_open(struct cdev *dev, int flag, int mode, struct thread *td)
+hvcn_open(struct tty *tp)
 {
-	struct	tty *tp;
-	int	error, setuptimeout;
-
-	setuptimeout = 0;
-
-	if (dev->si_tty == NULL) {
-		hvcn_tp = ttyalloc();
-		dev->si_tty = hvcn_tp;
-		hvcn_tp->t_dev = dev;
-	}
-	tp = dev->si_tty;
-
-	tp->t_oproc = hvcn_tty_start;
-	tp->t_param = hvcn_tty_param;
-	tp->t_stop = hvcn_tty_stop;
 
-	if ((tp->t_state & TS_ISOPEN) == 0) {
-		tp->t_state |= TS_CARR_ON;
-		ttyconsolemode(tp, 0);
-
-		setuptimeout = 1;
-	} else if ((tp->t_state & TS_XCLUDE) && priv_check(td,
-	     PRIV_TTY_EXCLUSIVE)) {
-		return (EBUSY);
-	}
-
-	error = ttyld_open(tp, dev);
-#if defined(SIMULATOR) || 1
-	if (error == 0 && setuptimeout) {
-		int polltime;
+	/*
+	 * Set up timeout to trigger fake interrupts to transmit
+	 * trailing data.
+	 */
+	polltime = hz / HVCN_POLL_FREQ;
+	if (polltime < 1)
+		polltime = 1;
+	hvcn_timeouthandle = timeout(hvcn_timeout, tp, polltime);
 
-		polltime = hz / HVCN_POLL_FREQ;
-		if (polltime < 1) {
-			polltime = 1;
-		}
+	buflen = 0;
 
-		hvcn_timeouthandle = timeout(hvcn_timeout, tp, polltime);
-	}
-#endif
-	return (error);
+	return (0);
 }
  
-static int
-hvcn_close(struct cdev *dev, int flag, int mode, struct thread *td)
+static void
+hvcn_close(struct tty *tp)
 {
-	int	unit;
-	struct	tty *tp;
-
-	unit = minor(dev);
-	tp = dev->si_tty;
-
-	if (unit != 0) 
-		return (ENXIO);
-	
 	untimeout(hvcn_timeout, tp, hvcn_timeouthandle);
-	ttyld_close(tp, flag);
-	tty_close(tp);
-
-	return (0);
 }
 
 static void
@@ -210,7 +165,8 @@ done:
 static void
 hvcn_cninit(struct consdev *cp)
 {
-	sprintf(cp->cn_name, "hvcn");
+
+	strcpy(cp->cn_name, "hvcn");
 }
 
 static int
@@ -295,64 +251,43 @@ hvcn_cnputc(struct consdev *cp, int c)
 	} while (error == H_EWOULDBLOCK);
 }
 
-static int
-hvcn_tty_param(struct tty *tp, struct termios *t)
-{
-        tp->t_ispeed = t->c_ispeed;
-        tp->t_ospeed = t->c_ospeed;
-        tp->t_cflag = t->c_cflag;
-
-	return (0);
-}
-
 static void
-hvcn_tty_start(struct tty *tp)
+hvcn_outwakeup(struct tty *tp)
 {
 
-        if (!(tp->t_state & (TS_TIMEOUT | TS_BUSY | TS_TTSTOP))) {
-		tp->t_state |= TS_BUSY;
+	for (;;) {
+		/* Refill the input buffer. */
+		if (buflen == 0) {
+			buflen = ttydisc_getc(tp, buf, PCBURST);
+			bufindex = 0;
+		}
 
-		do {
-			if (buflen == 0) {
-				buflen = q_to_b(&tp->t_outq, buf, PCBURST);
-				bufindex = 0;
-			}
-			while (buflen) {
-				if (hv_cons_putchar(buf[bufindex]) == H_EWOULDBLOCK)
-					goto done;
-				bufindex++;
-				buflen--;
-			}
-		} while (tp->t_outq.c_cc != 0);
-	done:
-		tp->t_state &= ~TS_BUSY;
-		ttwwakeup(tp);
+		/* Transmit the input buffer. */
+		while (buflen) {
+			if (hv_cons_putchar(buf[bufindex]) == H_EWOULDBLOCK)
+				return;
+			bufindex++;
+			buflen--;
+		}
 	}
 }
 
 static void
-hvcn_tty_stop(struct tty *tp, int flag)
-{
-	if ((tp->t_state & TS_BUSY) && !(tp->t_state & TS_TTSTOP)) 
-		tp->t_state |= TS_FLUSH;
-		
-	
-}
-
-static void
 hvcn_intr(void *v)
 {
-	struct tty *tp;
+	struct tty *tp = v;
 	int c;
 
-	tp = (struct tty *)v;
+	tty_lock(tp);
 	
+	/* Receive data. */
 	while ((c = hvcn_cncheckc(NULL)) != -1) 
-		if (tp->t_state & TS_ISOPEN) 
-			ttyld_rint(tp, c);
+		ttydisc_rint(tp, c, 0);
+	ttydisc_rint_done(tp);
 
-	if (tp->t_outq.c_cc != 0 || buflen != 0) 
-		hvcn_tty_start(tp);
+	/* Transmit trailing data. */
+	hvcn_outwakeup(tp);
+	tty_unlock(tp);
 }
 
 static void
@@ -381,7 +316,7 @@ static int
 hvcn_dev_attach(device_t dev)
 {
       
-	struct cdev *cdev;
+	struct tty *tp;
 	int error, rid;
 
 	/* belongs in attach - but attach is getting called multiple times
@@ -392,8 +327,9 @@ hvcn_dev_attach(device_t dev)
 	    hvcn_consdev.cn_name[0] == '\0') 
 		return (ENXIO);
 
-	cdev = make_dev(&hvcn_cdevsw, 0, UID_ROOT, GID_WHEEL, 0600, "ttyv%r", 1);
-	make_dev_alias(cdev, "hvcn");
+	tp = tty_alloc(&hvcn_class, NULL, NULL);
+	tty_makedev(tp, NULL, "v%r", 1);
+	tty_makealias(tp, "hvcn");
 	
 	rid = 0;