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, 73 insertions, 95 deletions

diff --git a/sys/dev/uart/uart_core.c b/sys/dev/uart/uart_core.c
index 3b0d64c..932c08a 100644
--- a/sys/dev/uart/uart_core.c
+++ b/sys/dev/uart/uart_core.c
@@ -46,7 +46,6 @@ __FBSDID("$FreeBSD$");
 #include <machine/bus.h>
 #include <sys/rman.h>
 #include <sys/termios.h>
-#include <sys/tty.h>
 #include <machine/resource.h>
 #include <machine/stdarg.h>
 
@@ -466,7 +465,7 @@ uart_bus_attach(device_t dev)
 		sc->sc_polled = 1;
 	}
 
-	sc->sc_rxbufsz = IBUFSIZ;
+	sc->sc_rxbufsz = 384;
 	sc->sc_rxbuf = malloc(sc->sc_rxbufsz * sizeof(*sc->sc_rxbuf),
 	    M_UART, M_WAITOK);
 	sc->sc_txbuf = malloc(sc->sc_txfifosz * sizeof(*sc->sc_txbuf),
diff --git a/sys/dev/uart/uart_tty.c b/sys/dev/uart/uart_tty.c
index 1971049..9b37bb3 100644
--- a/sys/dev/uart/uart_tty.c
+++ b/sys/dev/uart/uart_tty.c
@@ -123,11 +123,11 @@ uart_cngetc(struct consdev *cp)
 }
 
 static int
-uart_tty_open(struct tty *tp, struct cdev *dev)
+uart_tty_open(struct tty *tp)
 {
 	struct uart_softc *sc;
 
-	sc = tp->t_sc;
+	sc = tty_softc(tp);
 
 	if (sc == NULL || sc->sc_leaving)
 		return (ENXIO);
@@ -141,7 +141,7 @@ uart_tty_close(struct tty *tp)
 {
 	struct uart_softc *sc;
 
-	sc = tp->t_sc;
+	sc = tty_softc(tp);
 	if (sc == NULL || sc->sc_leaving || !sc->sc_opened) 
 		return;
 
@@ -158,11 +158,11 @@ uart_tty_close(struct tty *tp)
 }
 
 static void
-uart_tty_oproc(struct tty *tp)
+uart_tty_outwakeup(struct tty *tp)
 {
 	struct uart_softc *sc;
 
-	sc = tp->t_sc;
+	sc = tty_softc(tp);
 	if (sc == NULL || sc->sc_leaving)
 		return;
 
@@ -173,30 +173,45 @@ uart_tty_oproc(struct tty *tp)
 	 * de-assert RTS for us. In that situation we're completely stuffed.
 	 * Without hardware support, we need to toggle RTS ourselves.
 	 */
-	if ((tp->t_cflag & CRTS_IFLOW) && !sc->sc_hwiflow) {
-		if ((tp->t_state & TS_TBLOCK) &&
+	if ((tp->t_termios.c_cflag & CRTS_IFLOW) && !sc->sc_hwiflow) {
+#if 0
+		/*if ((tp->t_state & TS_TBLOCK) &&
 		    (sc->sc_hwsig & SER_RTS))
 			UART_SETSIG(sc, SER_DRTS);
-		else if (!(tp->t_state & TS_TBLOCK) &&
+		else */ if (/*!(tp->t_state & TS_TBLOCK) &&*/
 		    !(sc->sc_hwsig & SER_RTS))
 			UART_SETSIG(sc, SER_DRTS|SER_RTS);
+#endif
+		/* XXX: we should use inwakeup to implement this! */
+		if (!(sc->sc_hwsig & SER_RTS))
+			UART_SETSIG(sc, SER_DRTS|SER_RTS);
 	}
 
-	if (tp->t_state & TS_TTSTOP)
+	if (sc->sc_txbusy)
 		return;
 
-	if ((tp->t_state & TS_BUSY) || sc->sc_txbusy)
-		return;
+	sc->sc_txdatasz = ttydisc_getc(tp, sc->sc_txbuf, sc->sc_txfifosz);
+	if (sc->sc_txdatasz != 0)
+		UART_TRANSMIT(sc);
+}
 
-	if (tp->t_outq.c_cc == 0) {
-		ttwwakeup(tp);
-		return;
-	}
+static int
+uart_tty_ioctl(struct tty *tp, u_long cmd, caddr_t data, struct thread *td)
+{
+	struct uart_softc *sc;
+
+	sc = tty_softc(tp);
 
-	sc->sc_txdatasz = q_to_b(&tp->t_outq, sc->sc_txbuf, sc->sc_txfifosz);
-	tp->t_state |= TS_BUSY;
-	UART_TRANSMIT(sc);
-	ttwwakeup(tp);
+	switch (cmd) {
+	case TIOCSBRK:
+		UART_IOCTL(sc, UART_IOCTL_BREAK, 1);
+		return (0);
+	case TIOCCBRK:
+		UART_IOCTL(sc, UART_IOCTL_BREAK, 0);
+		return (0);
+	default:
+		return pps_ioctl(cmd, data, &sc->sc_pps);
+	}
 }
 
 static int
@@ -205,7 +220,7 @@ uart_tty_param(struct tty *tp, struct termios *t)
 	struct uart_softc *sc;
 	int databits, parity, stopbits;
 
-	sc = tp->t_sc;
+	sc = tty_softc(tp);
 	if (sc == NULL || sc->sc_leaving)
 		return (ENODEV);
 	if (t->c_ispeed != t->c_ospeed && t->c_ospeed != 0)
@@ -237,16 +252,16 @@ uart_tty_param(struct tty *tp, struct termios *t)
 	UART_SETSIG(sc, SER_DDTR | SER_DTR);
 	/* Set input flow control state. */
 	if (!sc->sc_hwiflow) {
-		if ((t->c_cflag & CRTS_IFLOW) && (tp->t_state & TS_TBLOCK))
+		/* if ((t->c_cflag & CRTS_IFLOW) && (tp->t_state & TS_TBLOCK))
 			UART_SETSIG(sc, SER_DRTS);
-		else
+		else */
 			UART_SETSIG(sc, SER_DRTS | SER_RTS);
 	} else
 		UART_IOCTL(sc, UART_IOCTL_IFLOW, (t->c_cflag & CRTS_IFLOW));
 	/* Set output flow control state. */
 	if (sc->sc_hwoflow)
 		UART_IOCTL(sc, UART_IOCTL_OFLOW, (t->c_cflag & CCTS_OFLOW));
-	ttsetwater(tp);
+
 	return (0);
 }
 
@@ -255,48 +270,18 @@ uart_tty_modem(struct tty *tp, int biton, int bitoff)
 {
 	struct uart_softc *sc;
 
-	sc = tp->t_sc;
+	sc = tty_softc(tp);
 	if (biton != 0 || bitoff != 0)
 		UART_SETSIG(sc, SER_DELTA(bitoff|biton) | biton);
 	return (sc->sc_hwsig);
 }
 
-static void
-uart_tty_break(struct tty *tp, int state)
-{
-	struct uart_softc *sc;
-
-	sc = tp->t_sc;
-	UART_IOCTL(sc, UART_IOCTL_BREAK, state);
-}
-
-static void
-uart_tty_stop(struct tty *tp, int rw)
-{
-	struct uart_softc *sc;
-
-	sc = tp->t_sc;
-	if (sc == NULL || sc->sc_leaving)
-		return;
-	if (rw & FWRITE) {
-		if (sc->sc_txbusy) {
-			sc->sc_txbusy = 0;
-			UART_FLUSH(sc, UART_FLUSH_TRANSMITTER);
-		}
-		tp->t_state &= ~TS_BUSY;
-	}
-	if (rw & FREAD) {
-		UART_FLUSH(sc, UART_FLUSH_RECEIVER);
-		sc->sc_rxget = sc->sc_rxput = 0;
-	}
-}
-
 void
 uart_tty_intr(void *arg)
 {
 	struct uart_softc *sc = arg;
 	struct tty *tp;
-	int c, pend, sig, xc;
+	int c, err = 0, pend, sig, xc;
 
 	if (sc->sc_leaving)
 		return;
@@ -306,78 +291,72 @@ uart_tty_intr(void *arg)
 		return;
 
 	tp = sc->sc_u.u_tty.tp;
+	tty_lock(tp);
 
 	if (pend & SER_INT_RXREADY) {
-		while (!uart_rx_empty(sc) && !(tp->t_state & TS_TBLOCK)) {
+		while (!uart_rx_empty(sc) /* && !(tp->t_state & TS_TBLOCK)*/) {
 			xc = uart_rx_get(sc);
 			c = xc & 0xff;
 			if (xc & UART_STAT_FRAMERR)
-				c |= TTY_FE;
+				err |= TRE_FRAMING;
 			if (xc & UART_STAT_OVERRUN)
-				c |= TTY_OE;
+				err |= TRE_OVERRUN;
 			if (xc & UART_STAT_PARERR)
-				c |= TTY_PE;
-			ttyld_rint(tp, c);
+				err |= TRE_PARITY;
+			ttydisc_rint(tp, c, err);
 		}
 	}
 
-	if (pend & SER_INT_BREAK) {
-		if (tp != NULL && !(tp->t_iflag & IGNBRK))
-			ttyld_rint(tp, 0);
-	}
+	if (pend & SER_INT_BREAK)
+		ttydisc_rint(tp, 0, TRE_BREAK);
 
 	if (pend & SER_INT_SIGCHG) {
 		sig = pend & SER_INT_SIGMASK;
 		if (sig & SER_DDCD)
-			ttyld_modem(tp, sig & SER_DCD);
-		if ((sig & SER_DCTS) && (tp->t_cflag & CCTS_OFLOW) &&
+			ttydisc_modem(tp, sig & SER_DCD);
+		if ((sig & SER_DCTS) && (tp->t_termios.c_cflag & CCTS_OFLOW) &&
 		    !sc->sc_hwoflow) {
-			if (sig & SER_CTS) {
-				tp->t_state &= ~TS_TTSTOP;
-				ttyld_start(tp);
-			} else
-				tp->t_state |= TS_TTSTOP;
+			if (sig & SER_CTS)
+				uart_tty_outwakeup(tp);
 		}
 	}
 
-	if (pend & SER_INT_TXIDLE) {
-		tp->t_state &= ~TS_BUSY;
-		ttyld_start(tp);
-	}
+	if (pend & SER_INT_TXIDLE)
+		uart_tty_outwakeup(tp);
+	ttydisc_rint_done(tp);
+	tty_unlock(tp);
 }
 
+static struct ttydevsw uart_tty_class = {
+	.tsw_flags	= TF_INITLOCK|TF_CALLOUT,
+	.tsw_open	= uart_tty_open,
+	.tsw_close	= uart_tty_close,
+	.tsw_outwakeup	= uart_tty_outwakeup,
+	.tsw_ioctl	= uart_tty_ioctl,
+	.tsw_param	= uart_tty_param,
+	.tsw_modem	= uart_tty_modem,
+};
+
 int
 uart_tty_attach(struct uart_softc *sc)
 {
 	struct tty *tp;
 	int unit;
 
-	tp = ttyalloc();
-	sc->sc_u.u_tty.tp = tp;
-	tp->t_sc = sc;
+	sc->sc_u.u_tty.tp = tp = tty_alloc(&uart_tty_class, sc, NULL);
 
 	unit = device_get_unit(sc->sc_dev);
 
-	tp->t_oproc = uart_tty_oproc;
-	tp->t_param = uart_tty_param;
-	tp->t_stop = uart_tty_stop;
-	tp->t_modem = uart_tty_modem;
-	tp->t_break = uart_tty_break;
-	tp->t_open = uart_tty_open;
-	tp->t_close = uart_tty_close;
-
-	tp->t_pps = &sc->sc_pps;
-
 	if (sc->sc_sysdev != NULL && sc->sc_sysdev->type == UART_DEV_CONSOLE) {
 		sprintf(((struct consdev *)sc->sc_sysdev->cookie)->cn_name,
 		    "ttyu%r", unit);
-		ttyconsolemode(tp, 0);
+		tty_init_console(tp, 0);
 	}
 
 	swi_add(&tty_intr_event, uart_driver_name, uart_tty_intr, sc, SWI_TTY,
 	    INTR_TYPE_TTY, &sc->sc_softih);
 
-	ttycreate(tp, TS_CALLOUT, "u%r", unit);
+	tty_makedev(tp, NULL, "u%r", unit);
 
 	return (0);
 }
@@ -387,10 +366,10 @@ int uart_tty_detach(struct uart_softc *sc)
 	struct tty *tp;
 
 	tp = sc->sc_u.u_tty.tp;
-	tp->t_pps = NULL;
-	ttygone(tp);
+
+	tty_lock(tp);
 	swi_remove(sc->sc_softih);
-	ttyfree(tp);
+	tty_rel_gone(tp);
 
 	return (0);
 }