tty: The big operations rework

- Operations are now a shared const function block as with most other Linux
  objects

- Introduce wrappers for some optional functions to get consistent behaviour

- Wrap put_char which used to be patched by the tty layer

- Document which functions are needed/optional

- Make put_char report success/fail

- Cache the driver->ops pointer in the tty as tty->ops

- Remove various surplus lock calls we no longer need

- Remove proc_write method as noted by Alexey Dobriyan

- Introduce some missing sanity checks where certain driver/ldisc
  combinations would oops as they didn't check needed methods were present

[akpm@linux-foundation.org: fix fs/compat_ioctl.c build]
[akpm@linux-foundation.org: fix isicom]
[akpm@linux-foundation.org: fix arch/ia64/hp/sim/simserial.c build]
[akpm@linux-foundation.org: fix kgdb]
Signed-off-by: Alan Cox <alan@redhat.com>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Cc: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

8 files changed, 183 insertions, 213 deletions

diff --git a/drivers/char/ip2/ip2main.c b/drivers/char/ip2/ip2main.c
index c4f4ca3..5ef69dc 100644
--- a/drivers/char/ip2/ip2main.c
+++ b/drivers/char/ip2/ip2main.c
@@ -169,7 +169,7 @@ static int Fip_firmware_size;
 static int  ip2_open(PTTY, struct file *);
 static void ip2_close(PTTY, struct file *);
 static int  ip2_write(PTTY, const unsigned char *, int);
-static void ip2_putchar(PTTY, unsigned char);
+static int  ip2_putchar(PTTY, unsigned char);
 static void ip2_flush_chars(PTTY);
 static int  ip2_write_room(PTTY);
 static int  ip2_chars_in_buf(PTTY);
@@ -1616,10 +1616,9 @@ ip2_close( PTTY tty, struct file *pFile )
 
 	serviceOutgoingFifo ( pCh->pMyBord );
 
-	if ( tty->driver->flush_buffer ) 
-		tty->driver->flush_buffer(tty);
-	if ( tty->ldisc.flush_buffer )  
-		tty->ldisc.flush_buffer(tty);
+	if ( tty->driver->ops->flush_buffer )
+		tty->driver->ops->flush_buffer(tty);
+	tty_ldisc_flush(tty);
 	tty->closing = 0;
 	
 	pCh->pTTY = NULL;
@@ -1738,7 +1737,7 @@ ip2_write( PTTY tty, const unsigned char *pData, int count)
 /*                                                                            */
 /*                                                                            */
 /******************************************************************************/
-static void
+static int
 ip2_putchar( PTTY tty, unsigned char ch )
 {
 	i2ChanStrPtr  pCh = tty->driver_data;
@@ -1753,6 +1752,7 @@ ip2_putchar( PTTY tty, unsigned char ch )
 		ip2_flush_chars( tty );
 	} else
 		write_unlock_irqrestore(&pCh->Pbuf_spinlock, flags);
+	return 1;
 
 //	ip2trace (CHANN, ITRC_PUTC, ITRC_RETURN, 1, ch );
 }
diff --git a/drivers/char/isicom.c b/drivers/char/isicom.c
index 57b1152..9c6be8d 100644
--- a/drivers/char/isicom.c
+++ b/drivers/char/isicom.c
@@ -1140,28 +1140,29 @@ static int isicom_write(struct tty_struct *tty,	const unsigned char *buf,
 }
 
 /* put_char et all */
-static void isicom_put_char(struct tty_struct *tty, unsigned char ch)
+static int isicom_put_char(struct tty_struct *tty, unsigned char ch)
 {
 	struct isi_port *port = tty->driver_data;
 	struct isi_board *card = port->card;
 	unsigned long flags;
 
 	if (isicom_paranoia_check(port, tty->name, "isicom_put_char"))
-		return;
+		return 0;
 
 	if (!port->xmit_buf)
-		return;
+		return 0;
 
 	spin_lock_irqsave(&card->card_lock, flags);
-	if (port->xmit_cnt >= SERIAL_XMIT_SIZE - 1)
-		goto out;
+	if (port->xmit_cnt >= SERIAL_XMIT_SIZE - 1) {
+		spin_unlock_irqrestore(&card->card_lock, flags);
+		return 0;
+	}
 
 	port->xmit_buf[port->xmit_head++] = ch;
 	port->xmit_head &= (SERIAL_XMIT_SIZE - 1);
 	port->xmit_cnt++;
 	spin_unlock_irqrestore(&card->card_lock, flags);
-out:
-	return;
+	return 1;
 }
 
 /* flush_chars et all */
diff --git a/drivers/char/keyboard.c b/drivers/char/keyboard.c
index 60b934a..d1c50b3 100644
--- a/drivers/char/keyboard.c
+++ b/drivers/char/keyboard.c
@@ -1230,7 +1230,7 @@ static void kbd_keycode(unsigned int keycode, int down, int hw_raw)
 
 	if (rep &&
 	    (!vc_kbd_mode(kbd, VC_REPEAT) ||
-	     (tty && !L_ECHO(tty) && tty->driver->chars_in_buffer(tty)))) {
+	     (tty && !L_ECHO(tty) && tty_chars_in_buffer(tty)))) {
 		/*
 		 * Don't repeat a key if the input buffers are not empty and the
 		 * characters get aren't echoed locally. This makes key repeat
diff --git a/drivers/char/n_hdlc.c b/drivers/char/n_hdlc.c
index a07c0af..a35bfd7 100644
--- a/drivers/char/n_hdlc.c
+++ b/drivers/char/n_hdlc.c
@@ -342,12 +342,10 @@ static int n_hdlc_tty_open (struct tty_struct *tty)
 #endif
 	
 	/* Flush any pending characters in the driver and discipline. */
-	
 	if (tty->ldisc.flush_buffer)
-		tty->ldisc.flush_buffer (tty);
+		tty->ldisc.flush_buffer(tty);
 
-	if (tty->driver->flush_buffer)
-		tty->driver->flush_buffer (tty);
+	tty_driver_flush_buffer(tty);
 		
 	if (debuglevel >= DEBUG_LEVEL_INFO)	
 		printk("%s(%d)n_hdlc_tty_open() success\n",__FILE__,__LINE__);
@@ -399,7 +397,7 @@ static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)
 			
 		/* Send the next block of data to device */
 		tty->flags |= (1 << TTY_DO_WRITE_WAKEUP);
-		actual = tty->driver->write(tty, tbuf->buf, tbuf->count);
+		actual = tty->ops->write(tty, tbuf->buf, tbuf->count);
 
 		/* rollback was possible and has been done */
 		if (actual == -ERESTARTSYS) {
@@ -752,8 +750,7 @@ static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
 
 	case TIOCOUTQ:
 		/* get the pending tx byte count in the driver */
-		count = tty->driver->chars_in_buffer ?
-				tty->driver->chars_in_buffer(tty) : 0;
+		count = tty_chars_in_buffer(tty);
 		/* add size of next output frame in queue */
 		spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock,flags);
 		if (n_hdlc->tx_buf_list.head)
diff --git a/drivers/char/n_r3964.c b/drivers/char/n_r3964.c
index 3f6486e..9021690 100644
--- a/drivers/char/n_r3964.c
+++ b/drivers/char/n_r3964.c
@@ -376,8 +376,9 @@ static void put_char(struct r3964_info *pInfo, unsigned char ch)
 	if (tty == NULL)
 		return;
 
-	if (tty->driver->put_char) {
-		tty->driver->put_char(tty, ch);
+	/* FIXME: put_char should not be called from an IRQ */
+	if (tty->ops->put_char) {
+		tty->ops->put_char(tty, ch);
 	}
 	pInfo->bcc ^= ch;
 }
@@ -386,12 +387,9 @@ static void flush(struct r3964_info *pInfo)
 {
 	struct tty_struct *tty = pInfo->tty;
 
-	if (tty == NULL)
+	if (tty == NULL || tty->ops->flush_chars == NULL)
 		return;
-
-	if (tty->driver->flush_chars) {
-		tty->driver->flush_chars(tty);
-	}
+	tty->ops->flush_chars(tty);
 }
 
 static void trigger_transmit(struct r3964_info *pInfo)
@@ -449,12 +447,11 @@ static void transmit_block(struct r3964_info *pInfo)
 	struct r3964_block_header *pBlock = pInfo->tx_first;
 	int room = 0;
 
-	if ((tty == NULL) || (pBlock == NULL)) {
+	if (tty == NULL || pBlock == NULL) {
 		return;
 	}
 
-	if (tty->driver->write_room)
-		room = tty->driver->write_room(tty);
+	room = tty_write_room(tty);
 
 	TRACE_PS("transmit_block %p, room %d, length %d",
 		 pBlock, room, pBlock->length);
diff --git a/drivers/char/n_tty.c b/drivers/char/n_tty.c
index e1518e1..abc93a9 100644
--- a/drivers/char/n_tty.c
+++ b/drivers/char/n_tty.c
@@ -149,8 +149,8 @@ static void check_unthrottle(struct tty_struct *tty)
 {
 	if (tty->count &&
 	    test_and_clear_bit(TTY_THROTTLED, &tty->flags) &&
-	    tty->driver->unthrottle)
-		tty->driver->unthrottle(tty);
+	    tty->ops->unthrottle)
+		tty->ops->unthrottle(tty);
 }
 
 /**
@@ -273,7 +273,7 @@ static int opost(unsigned char c, struct tty_struct *tty)
 {
 	int	space, spaces;
 
-	space = tty->driver->write_room(tty);
+	space = tty_write_room(tty);
 	if (!space)
 		return -1;
 
@@ -286,7 +286,7 @@ static int opost(unsigned char c, struct tty_struct *tty)
 			if (O_ONLCR(tty)) {
 				if (space < 2)
 					return -1;
-				tty->driver->put_char(tty, '\r');
+				tty_put_char(tty, '\r');
 				tty->column = 0;
 			}
 			tty->canon_column = tty->column;
@@ -308,7 +308,7 @@ static int opost(unsigned char c, struct tty_struct *tty)
 				if (space < spaces)
 					return -1;
 				tty->column += spaces;
-				tty->driver->write(tty, "        ", spaces);
+				tty->ops->write(tty, "        ", spaces);
 				return 0;
 			}
 			tty->column += spaces;
@@ -325,7 +325,7 @@ static int opost(unsigned char c, struct tty_struct *tty)
 			break;
 		}
 	}
-	tty->driver->put_char(tty, c);
+	tty_put_char(tty, c);
 	unlock_kernel();
 	return 0;
 }
@@ -352,7 +352,7 @@ static ssize_t opost_block(struct tty_struct *tty,
 	int 	i;
 	const unsigned char *cp;
 
-	space = tty->driver->write_room(tty);
+	space = tty_write_room(tty);
 	if (!space)
 		return 0;
 	if (nr > space)
@@ -390,28 +390,15 @@ static ssize_t opost_block(struct tty_struct *tty,
 		}
 	}
 break_out:
-	if (tty->driver->flush_chars)
-		tty->driver->flush_chars(tty);
-	i = tty->driver->write(tty, buf, i);
+	if (tty->ops->flush_chars)
+		tty->ops->flush_chars(tty);
+	i = tty->ops->write(tty, buf, i);
 	unlock_kernel();
 	return i;
 }
 
 
 /**
- *	put_char	-	write character to driver
- *	@c: character (or part of unicode symbol)
- *	@tty: terminal device
- *
- *	Queue a byte to the driver layer for output
- */
-
-static inline void put_char(unsigned char c, struct tty_struct *tty)
-{
-	tty->driver->put_char(tty, c);
-}
-
-/**
  *	echo_char	-	echo characters
  *	@c: unicode byte to echo
  *	@tty: terminal device
@@ -423,8 +410,8 @@ static inline void put_char(unsigned char c, struct tty_struct *tty)
 static void echo_char(unsigned char c, struct tty_struct *tty)
 {
 	if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t') {
-		put_char('^', tty);
-		put_char(c ^ 0100, tty);
+		tty_put_char(tty, '^');
+		tty_put_char(tty, c ^ 0100);
 		tty->column += 2;
 	} else
 		opost(c, tty);
@@ -433,7 +420,7 @@ static void echo_char(unsigned char c, struct tty_struct *tty)
 static inline void finish_erasing(struct tty_struct *tty)
 {
 	if (tty->erasing) {
-		put_char('/', tty);
+		tty_put_char(tty, '/');
 		tty->column++;
 		tty->erasing = 0;
 	}
@@ -517,7 +504,7 @@ static void eraser(unsigned char c, struct tty_struct *tty)
 		if (L_ECHO(tty)) {
 			if (L_ECHOPRT(tty)) {
 				if (!tty->erasing) {
-					put_char('\\', tty);
+					tty_put_char(tty, '\\');
 					tty->column++;
 					tty->erasing = 1;
 				}
@@ -525,7 +512,7 @@ static void eraser(unsigned char c, struct tty_struct *tty)
 				echo_char(c, tty);
 				while (--cnt > 0) {
 					head = (head+1) & (N_TTY_BUF_SIZE-1);
-					put_char(tty->read_buf[head], tty);
+					tty_put_char(tty, tty->read_buf[head]);
 				}
 			} else if (kill_type == ERASE && !L_ECHOE(tty)) {
 				echo_char(ERASE_CHAR(tty), tty);
@@ -553,22 +540,22 @@ static void eraser(unsigned char c, struct tty_struct *tty)
 				/* Now backup to that column. */
 				while (tty->column > col) {
 					/* Can't use opost here. */
-					put_char('\b', tty);
+					tty_put_char(tty, '\b');
 					if (tty->column > 0)
 						tty->column--;
 				}
 			} else {
 				if (iscntrl(c) && L_ECHOCTL(tty)) {
-					put_char('\b', tty);
-					put_char(' ', tty);
-					put_char('\b', tty);
+					tty_put_char(tty, '\b');
+					tty_put_char(tty, ' ');
+					tty_put_char(tty, '\b');
 					if (tty->column > 0)
 						tty->column--;
 				}
 				if (!iscntrl(c) || L_ECHOCTL(tty)) {
-					put_char('\b', tty);
-					put_char(' ', tty);
-					put_char('\b', tty);
+					tty_put_char(tty, '\b');
+					tty_put_char(tty, ' ');
+					tty_put_char(tty, '\b');
 					if (tty->column > 0)
 						tty->column--;
 				}
@@ -599,8 +586,7 @@ static inline void isig(int sig, struct tty_struct *tty, int flush)
 		kill_pgrp(tty->pgrp, sig, 1);
 	if (flush || !L_NOFLSH(tty)) {
 		n_tty_flush_buffer(tty);
-		if (tty->driver->flush_buffer)
-			tty->driver->flush_buffer(tty);
+		tty_driver_flush_buffer(tty);
 	}
 }
 
@@ -732,7 +718,7 @@ static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
 		tty->lnext = 0;
 		if (L_ECHO(tty)) {
 			if (tty->read_cnt >= N_TTY_BUF_SIZE-1) {
-				put_char('\a', tty); /* beep if no space */
+				tty_put_char(tty, '\a'); /* beep if no space */
 				return;
 			}
 			/* Record the column of first canon char. */
@@ -776,8 +762,7 @@ send_signal:
 			 */
 			if (!L_NOFLSH(tty)) {
 				n_tty_flush_buffer(tty);
-				if (tty->driver->flush_buffer)
-					tty->driver->flush_buffer(tty);
+				tty_driver_flush_buffer(tty);
 			}
 			if (L_ECHO(tty))
 				echo_char(c, tty);
@@ -806,8 +791,8 @@ send_signal:
 			if (L_ECHO(tty)) {
 				finish_erasing(tty);
 				if (L_ECHOCTL(tty)) {
-					put_char('^', tty);
-					put_char('\b', tty);
+					tty_put_char(tty, '^');
+					tty_put_char(tty, '\b');
 				}
 			}
 			return;
@@ -828,7 +813,7 @@ send_signal:
 		if (c == '\n') {
 			if (L_ECHO(tty) || L_ECHONL(tty)) {
 				if (tty->read_cnt >= N_TTY_BUF_SIZE-1)
-					put_char('\a', tty);
+					tty_put_char(tty, '\a');
 				opost('\n', tty);
 			}
 			goto handle_newline;
@@ -846,7 +831,7 @@ send_signal:
 			 */
 			if (L_ECHO(tty)) {
 				if (tty->read_cnt >= N_TTY_BUF_SIZE-1)
-					put_char('\a', tty);
+					tty_put_char(tty, '\a');
 				/* Record the column of first canon char. */
 				if (tty->canon_head == tty->read_head)
 					tty->canon_column = tty->column;
@@ -876,7 +861,7 @@ handle_newline:
 	finish_erasing(tty);
 	if (L_ECHO(tty)) {
 		if (tty->read_cnt >= N_TTY_BUF_SIZE-1) {
-			put_char('\a', tty); /* beep if no space */
+			tty_put_char(tty, '\a'); /* beep if no space */
 			return;
 		}
 		if (c == '\n')
@@ -980,8 +965,8 @@ static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
 				break;
 			}
 		}
-		if (tty->driver->flush_chars)
-			tty->driver->flush_chars(tty);
+		if (tty->ops->flush_chars)
+			tty->ops->flush_chars(tty);
 	}
 
 	n_tty_set_room(tty);
@@ -1000,8 +985,8 @@ static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
 	if (tty->receive_room < TTY_THRESHOLD_THROTTLE) {
 		/* check TTY_THROTTLED first so it indicates our state */
 		if (!test_and_set_bit(TTY_THROTTLED, &tty->flags) &&
-		    tty->driver->throttle)
-			tty->driver->throttle(tty);
+		    tty->ops->throttle)
+			tty->ops->throttle(tty);
 	}
 }
 
@@ -1086,6 +1071,9 @@ static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
 			tty->real_raw = 0;
 	}
 	n_tty_set_room(tty);
+	/* The termios change make the tty ready for I/O */
+	wake_up_interruptible(&tty->write_wait);
+	wake_up_interruptible(&tty->read_wait);
 }
 
 /**
@@ -1513,11 +1501,11 @@ static ssize_t write_chan(struct tty_struct *tty, struct file *file,
 					break;
 				b++; nr--;
 			}
-			if (tty->driver->flush_chars)
-				tty->driver->flush_chars(tty);
+			if (tty->ops->flush_chars)
+				tty->ops->flush_chars(tty);
 		} else {
 			while (nr > 0) {
-				c = tty->driver->write(tty, b, nr);
+				c = tty->ops->write(tty, b, nr);
 				if (c < 0) {
 					retval = c;
 					goto break_out;
@@ -1554,11 +1542,6 @@ break_out:
  *
  *	This code must be sure never to sleep through a hangup.
  *	Called without the kernel lock held - fine
- *
- *	FIXME: if someone changes the VMIN or discipline settings for the
- *	terminal while another process is in poll() the poll does not
- *	recompute the new limits. Possibly set_termios should issue
- *	a read wakeup to fix this bug.
  */
 
 static unsigned int normal_poll(struct tty_struct *tty, struct file *file,
@@ -1582,9 +1565,9 @@ static unsigned int normal_poll(struct tty_struct *tty, struct file *file,
 		else
 			tty->minimum_to_wake = 1;
 	}
-	if (!tty_is_writelocked(tty) &&
-			tty->driver->chars_in_buffer(tty) < WAKEUP_CHARS &&
-			tty->driver->write_room(tty) > 0)
+	if (tty->ops->write && !tty_is_writelocked(tty) &&
+			tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
+			tty_write_room(tty) > 0)
 		mask |= POLLOUT | POLLWRNORM;
 	return mask;
 }
diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index b1692af..f69fb8d 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -1108,8 +1108,8 @@ restart:
 	   a reference to the old ldisc. If we ended up flipping back
 	   to the existing ldisc we have two references to it */
 
-	if (tty->ldisc.num != o_ldisc.num && tty->driver->set_ldisc)
-		tty->driver->set_ldisc(tty);
+	if (tty->ldisc.num != o_ldisc.num && tty->ops->set_ldisc)
+		tty->ops->set_ldisc(tty);
 
 	tty_ldisc_put(o_ldisc.num);
 
@@ -1181,9 +1181,8 @@ struct tty_driver *tty_find_polling_driver(char *name, int *line)
 		if (*str == '\0')
 			str = NULL;
 
-		if (tty_line >= 0 && tty_line <= p->num && p->poll_init &&
-				!p->poll_init(p, tty_line, str)) {
-
+		if (tty_line >= 0 && tty_line <= p->num && p->ops &&
+		    p->ops->poll_init && !p->ops->poll_init(p, tty_line, str)) {
 			res = p;
 			*line = tty_line;
 			break;
@@ -1452,8 +1451,7 @@ static void do_tty_hangup(struct work_struct *work)
 		/* We may have no line discipline at this point */
 		if (ld->flush_buffer)
 			ld->flush_buffer(tty);
-		if (tty->driver->flush_buffer)
-			tty->driver->flush_buffer(tty);
+		tty_driver_flush_buffer(tty);
 		if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) &&
 		    ld->write_wakeup)
 			ld->write_wakeup(tty);
@@ -1516,11 +1514,11 @@ static void do_tty_hangup(struct work_struct *work)
 	 * So we just call close() the right number of times.
 	 */
 	if (cons_filp) {
-		if (tty->driver->close)
+		if (tty->ops->close)
 			for (n = 0; n < closecount; n++)
-				tty->driver->close(tty, cons_filp);
-	} else if (tty->driver->hangup)
-		(tty->driver->hangup)(tty);
+				tty->ops->close(tty, cons_filp);
+	} else if (tty->ops->hangup)
+		(tty->ops->hangup)(tty);
 	/*
 	 * We don't want to have driver/ldisc interactions beyond
 	 * the ones we did here. The driver layer expects no
@@ -1752,8 +1750,8 @@ void stop_tty(struct tty_struct *tty)
 		wake_up_interruptible(&tty->link->read_wait);
 	}
 	spin_unlock_irqrestore(&tty->ctrl_lock, flags);
-	if (tty->driver->stop)
-		(tty->driver->stop)(tty);
+	if (tty->ops->stop)
+		(tty->ops->stop)(tty);
 }
 
 EXPORT_SYMBOL(stop_tty);
@@ -1786,8 +1784,8 @@ void start_tty(struct tty_struct *tty)
 		wake_up_interruptible(&tty->link->read_wait);
 	}
 	spin_unlock_irqrestore(&tty->ctrl_lock, flags);
-	if (tty->driver->start)
-		(tty->driver->start)(tty);
+	if (tty->ops->start)
+		(tty->ops->start)(tty);
 	/* If we have a running line discipline it may need kicking */
 	tty_wakeup(tty);
 }
@@ -1972,10 +1970,13 @@ static ssize_t tty_write(struct file *file, const char __user *buf,
 	tty = (struct tty_struct *)file->private_data;
 	if (tty_paranoia_check(tty, inode, "tty_write"))
 		return -EIO;
-	if (!tty || !tty->driver->write ||
+	if (!tty || !tty->ops->write ||
 		(test_bit(TTY_IO_ERROR, &tty->flags)))
 			return -EIO;
-
+	/* Short term debug to catch buggy drivers */
+	if (tty->ops->write_room == NULL)
+		printk(KERN_ERR "tty driver %s lacks a write_room method.\n",
+			tty->driver->name);
 	ld = tty_ldisc_ref_wait(tty);
 	if (!ld->write)
 		ret = -EIO;
@@ -2122,6 +2123,7 @@ static int init_dev(struct tty_driver *driver, int idx,
 		goto fail_no_mem;
 	initialize_tty_struct(tty);
 	tty->driver = driver;
+	tty->ops = driver->ops;
 	tty->index = idx;
 	tty_line_name(driver, idx, tty->name);
 
@@ -2152,6 +2154,7 @@ static int init_dev(struct tty_driver *driver, int idx,
 			goto free_mem_out;
 		initialize_tty_struct(o_tty);
 		o_tty->driver = driver->other;
+		o_tty->ops = driver->ops;
 		o_tty->index = idx;
 		tty_line_name(driver->other, idx, o_tty->name);
 
@@ -2456,8 +2459,8 @@ static void release_dev(struct file *filp)
 		}
 	}
 #endif
-	if (tty->driver->close)
-		tty->driver->close(tty, filp);
+	if (tty->ops->close)
+		tty->ops->close(tty, filp);
 
 	/*
 	 * Sanity check: if tty->count is going to zero, there shouldn't be
@@ -2740,8 +2743,8 @@ got_driver:
 	printk(KERN_DEBUG "opening %s...", tty->name);
 #endif
 	if (!retval) {
-		if (tty->driver->open)
-			retval = tty->driver->open(tty, filp);
+		if (tty->ops->open)
+			retval = tty->ops->open(tty, filp);
 		else
 			retval = -ENODEV;
 	}
@@ -2840,7 +2843,7 @@ static int ptmx_open(struct inode *inode, struct file *filp)
 		goto out1;
 
 	check_tty_count(tty, "tty_open");
-	retval = ptm_driver->open(tty, filp);
+	retval = ptm_driver->ops->open(tty, filp);
 	if (!retval)
 		return 0;
 out1:
@@ -3336,25 +3339,20 @@ static int tiocsetd(struct tty_struct *tty, int __user *p)
 
 static int send_break(struct tty_struct *tty, unsigned int duration)
 {
-	int retval = -EINTR;
-
-	lock_kernel();
 	if (tty_write_lock(tty, 0) < 0)
-		goto out;
-	tty->driver->break_ctl(tty, -1);
+		return -EINTR;
+	tty->ops->break_ctl(tty, -1);
 	if (!signal_pending(current))
 		msleep_interruptible(duration);
-	tty->driver->break_ctl(tty, 0);
+	tty->ops->break_ctl(tty, 0);
 	tty_write_unlock(tty);
 	if (!signal_pending(current))
-		retval = 0;
-out:
-	unlock_kernel();
-	return retval;
+		return -EINTR;
+	return 0;
 }
 
 /**
- *	tiocmget		-	get modem status
+ *	tty_tiocmget		-	get modem status
  *	@tty: tty device
  *	@file: user file pointer
  *	@p: pointer to result
@@ -3369,10 +3367,8 @@ static int tty_tiocmget(struct tty_struct *tty, struct file *file, int __user *p
 {
 	int retval = -EINVAL;
 
-	if (tty->driver->tiocmget) {
-		lock_kernel();
-		retval = tty->driver->tiocmget(tty, file);
-		unlock_kernel();
+	if (tty->ops->tiocmget) {
+		retval = tty->ops->tiocmget(tty, file);
 
 		if (retval >= 0)
 			retval = put_user(retval, p);
@@ -3381,7 +3377,7 @@ static int tty_tiocmget(struct tty_struct *tty, struct file *file, int __user *p
 }
 
 /**
- *	tiocmset		-	set modem status
+ *	tty_tiocmset		-	set modem status
  *	@tty: tty device
  *	@file: user file pointer
  *	@cmd: command - clear bits, set bits or set all
@@ -3398,7 +3394,7 @@ static int tty_tiocmset(struct tty_struct *tty, struct file *file, unsigned int
 {
 	int retval = -EINVAL;
 
-	if (tty->driver->tiocmset) {
+	if (tty->ops->tiocmset) {
 		unsigned int set, clear, val;
 
 		retval = get_user(val, p);
@@ -3422,9 +3418,7 @@ static int tty_tiocmset(struct tty_struct *tty, struct file *file, unsigned int
 		set &= TIOCM_DTR|TIOCM_RTS|TIOCM_OUT1|TIOCM_OUT2|TIOCM_LOOP;
 		clear &= TIOCM_DTR|TIOCM_RTS|TIOCM_OUT1|TIOCM_OUT2|TIOCM_LOOP;
 
-		lock_kernel();
-		retval = tty->driver->tiocmset(tty, file, set, clear);
-		unlock_kernel();
+		retval = tty->ops->tiocmset(tty, file, set, clear);
 	}
 	return retval;
 }
@@ -3455,23 +3449,25 @@ long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 
 	retval = -EINVAL;
 
-	if (!tty->driver->break_ctl) {
+	if (!tty->ops->break_ctl) {
 		switch (cmd) {
 		case TIOCSBRK:
 		case TIOCCBRK:
-			if (tty->driver->ioctl)
-				retval = tty->driver->ioctl(tty, file, cmd, arg);
+			if (tty->ops->ioctl)
+				retval = tty->ops->ioctl(tty, file, cmd, arg);
+			if (retval != -EINVAL && retval != -ENOIOCTLCMD)
+				printk(KERN_WARNING "tty: driver %s needs updating to use break_ctl\n", tty->driver->name);
 			return retval;
 
 		/* These two ioctl's always return success; even if */
 		/* the driver doesn't support them. */
 		case TCSBRK:
 		case TCSBRKP:
-			if (!tty->driver->ioctl)
+			if (!tty->ops->ioctl)
 				return 0;
-			lock_kernel();
-			retval = tty->driver->ioctl(tty, file, cmd, arg);
-			unlock_kernel();
+			retval = tty->ops->ioctl(tty, file, cmd, arg);
+			if (retval != -EINVAL && retval != -ENOIOCTLCMD)
+				printk(KERN_WARNING "tty: driver %s needs updating to use break_ctl\n", tty->driver->name);
 			if (retval == -ENOIOCTLCMD)
 				retval = 0;
 			return retval;
@@ -3491,9 +3487,7 @@ long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 		if (retval)
 			return retval;
 		if (cmd != TIOCCBRK) {
-			lock_kernel();
 			tty_wait_until_sent(tty, 0);
-			unlock_kernel();
 			if (signal_pending(current))
 				return -EINTR;
 		}
@@ -3531,7 +3525,6 @@ long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 	case TIOCGSID:
 		return tiocgsid(tty, real_tty, p);
 	case TIOCGETD:
-		/* FIXME: check this is ok */
 		return put_user(tty->ldisc.num, (int __user *)p);
 	case TIOCSETD:
 		return tiocsetd(tty, p);
@@ -3543,15 +3536,13 @@ long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 	 * Break handling
 	 */
 	case TIOCSBRK:	/* Turn break on, unconditionally */
-		lock_kernel();
-		tty->driver->break_ctl(tty, -1);
-		unlock_kernel();
+		if (tty->ops->break_ctl)
+			tty->ops->break_ctl(tty, -1);
 		return 0;
 
 	case TIOCCBRK:	/* Turn break off, unconditionally */
-		lock_kernel();
-		tty->driver->break_ctl(tty, 0);
-		unlock_kernel();
+		if (tty->ops->break_ctl)
+			tty->ops->break_ctl(tty, 0);
 		return 0;
 	case TCSBRK:   /* SVID version: non-zero arg --> no break */
 		/* non-zero arg means wait for all output data
@@ -3580,8 +3571,8 @@ long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 		}
 		break;
 	}
-	if (tty->driver->ioctl) {
-		retval = (tty->driver->ioctl)(tty, file, cmd, arg);
+	if (tty->ops->ioctl) {
+		retval = (tty->ops->ioctl)(tty, file, cmd, arg);
 		if (retval != -ENOIOCTLCMD)
 			return retval;
 	}
@@ -3608,8 +3599,8 @@ static long tty_compat_ioctl(struct file *file, unsigned int cmd,
 	if (tty_paranoia_check(tty, inode, "tty_ioctl"))
 		return -EINVAL;
 
-	if (tty->driver->compat_ioctl) {
-		retval = (tty->driver->compat_ioctl)(tty, file, cmd, arg);
+	if (tty->ops->compat_ioctl) {
+		retval = (tty->ops->compat_ioctl)(tty, file, cmd, arg);
 		if (retval != -ENOIOCTLCMD)
 			return retval;
 	}
@@ -3659,8 +3650,7 @@ void __do_SAK(struct tty_struct *tty)
 
 	tty_ldisc_flush(tty);
 
-	if (tty->driver->flush_buffer)
-		tty->driver->flush_buffer(tty);
+	tty_driver_flush_buffer(tty);
 
 	read_lock(&tasklist_lock);
 	/* Kill the entire session */
@@ -3871,15 +3861,27 @@ static void initialize_tty_struct(struct tty_struct *tty)
 	INIT_WORK(&tty->SAK_work, do_SAK_work);
 }
 
-/*
- * The default put_char routine if the driver did not define one.
+/**
+ *	tty_put_char	-	write one character to a tty
+ *	@tty: tty
+ *	@ch: character
+ *
+ *	Write one byte to the tty using the provided put_char method
+ *	if present. Returns the number of characters successfully output.
+ *
+ *	Note: the specific put_char operation in the driver layer may go
+ *	away soon. Don't call it directly, use this method
  */
 
-static void tty_default_put_char(struct tty_struct *tty, unsigned char ch)
+int tty_put_char(struct tty_struct *tty, unsigned char ch)
 {
-	tty->driver->write(tty, &ch, 1);
+	if (tty->ops->put_char)
+		return tty->ops->put_char(tty, ch);
+	return tty->ops->write(tty, &ch, 1);
 }
 
+EXPORT_SYMBOL_GPL(tty_put_char);
+
 static struct class *tty_class;
 
 /**
@@ -3962,37 +3964,8 @@ void put_tty_driver(struct tty_driver *driver)
 void tty_set_operations(struct tty_driver *driver,
 			const struct tty_operations *op)
 {
-	driver->open = op->open;
-	driver->close = op->close;
-	driver->write = op->write;
-	driver->put_char = op->put_char;
-	driver->flush_chars = op->flush_chars;
-	driver->write_room = op->write_room;
-	driver->chars_in_buffer = op->chars_in_buffer;
-	driver->ioctl = op->ioctl;
-	driver->compat_ioctl = op->compat_ioctl;
-	driver->set_termios = op->set_termios;
-	driver->throttle = op->throttle;
-	driver->unthrottle = op->unthrottle;
-	driver->stop = op->stop;
-	driver->start = op->start;
-	driver->hangup = op->hangup;
-	driver->break_ctl = op->break_ctl;
-	driver->flush_buffer = op->flush_buffer;
-	driver->set_ldisc = op->set_ldisc;
-	driver->wait_until_sent = op->wait_until_sent;
-	driver->send_xchar = op->send_xchar;
-	driver->read_proc = op->read_proc;
-	driver->write_proc = op->write_proc;
-	driver->tiocmget = op->tiocmget;
-	driver->tiocmset = op->tiocmset;
-#ifdef CONFIG_CONSOLE_POLL
-	driver->poll_init = op->poll_init;
-	driver->poll_get_char = op->poll_get_char;
-	driver->poll_put_char = op->poll_put_char;
-#endif
-}
-
+	driver->ops = op;
+};
 
 EXPORT_SYMBOL(alloc_tty_driver);
 EXPORT_SYMBOL(put_tty_driver);
@@ -4055,9 +4028,6 @@ int tty_register_driver(struct tty_driver *driver)
 		return error;
 	}
 
-	if (!driver->put_char)
-		driver->put_char = tty_default_put_char;
-
 	mutex_lock(&tty_mutex);
 	list_add(&driver->tty_drivers, &tty_drivers);
 	mutex_unlock(&tty_mutex);
diff --git a/drivers/char/tty_ioctl.c b/drivers/char/tty_ioctl.c
index 8c4bf3e..c10d40c 100644
--- a/drivers/char/tty_ioctl.c
+++ b/drivers/char/tty_ioctl.c
@@ -40,6 +40,34 @@
 #define TERMIOS_OLD	8
 
 
+int tty_chars_in_buffer(struct tty_struct *tty)
+{
+	if (tty->ops->chars_in_buffer)
+		return tty->ops->chars_in_buffer(tty);
+	else
+		return 0;
+}
+
+EXPORT_SYMBOL(tty_chars_in_buffer);
+
+int tty_write_room(struct tty_struct *tty)
+{
+	if (tty->ops->write_room)
+		return tty->ops->write_room(tty);
+	return 2048;
+}
+
+EXPORT_SYMBOL(tty_write_room);
+
+void tty_driver_flush_buffer(struct tty_struct *tty)
+{
+	if (tty->ops->flush_buffer)
+		tty->ops->flush_buffer(tty);
+}
+
+EXPORT_SYMBOL(tty_driver_flush_buffer);
+
+
 /**
  *	tty_wait_until_sent	-	wait for I/O to finish
  *	@tty: tty we are waiting for
@@ -58,17 +86,13 @@ void tty_wait_until_sent(struct tty_struct *tty, long timeout)
 
 	printk(KERN_DEBUG "%s wait until sent...\n", tty_name(tty, buf));
 #endif
-	if (!tty->driver->chars_in_buffer)
-		return;
 	if (!timeout)
 		timeout = MAX_SCHEDULE_TIMEOUT;
-	lock_kernel();
 	if (wait_event_interruptible_timeout(tty->write_wait,
-			!tty->driver->chars_in_buffer(tty), timeout) >= 0) {
-		if (tty->driver->wait_until_sent)
-			tty->driver->wait_until_sent(tty, timeout);
+			!tty_chars_in_buffer(tty), timeout) >= 0) {
+		if (tty->ops->wait_until_sent)
+			tty->ops->wait_until_sent(tty, timeout);
 	}
-	unlock_kernel();
 }
 EXPORT_SYMBOL(tty_wait_until_sent);
 
@@ -444,8 +468,8 @@ static void change_termios(struct tty_struct *tty, struct ktermios *new_termios)
 		}
 	}
 
-	if (tty->driver->set_termios)
-		(*tty->driver->set_termios)(tty, &old_termios);
+	if (tty->ops->set_termios)
+		(*tty->ops->set_termios)(tty, &old_termios);
 	else
 		tty_termios_copy_hw(tty->termios, &old_termios);
 
@@ -748,8 +772,8 @@ static int send_prio_char(struct tty_struct *tty, char ch)
 {
 	int	was_stopped = tty->stopped;
 
-	if (tty->driver->send_xchar) {
-		tty->driver->send_xchar(tty, ch);
+	if (tty->ops->send_xchar) {
+		tty->ops->send_xchar(tty, ch);
 		return 0;
 	}
 
@@ -758,7 +782,7 @@ static int send_prio_char(struct tty_struct *tty, char ch)
 
 	if (was_stopped)
 		start_tty(tty);
-	tty->driver->write(tty, &ch, 1);
+	tty->ops->write(tty, &ch, 1);
 	if (was_stopped)
 		stop_tty(tty);
 	tty_write_unlock(tty);
@@ -778,13 +802,14 @@ static int tty_change_softcar(struct tty_struct *tty, int arg)
 {
 	int ret = 0;
 	int bit = arg ? CLOCAL : 0;
-	struct ktermios old = *tty->termios;
+	struct ktermios old;
 
 	mutex_lock(&tty->termios_mutex);
+	old = *tty->termios;
 	tty->termios->c_cflag &= ~CLOCAL;
 	tty->termios->c_cflag |= bit;
-	if (tty->driver->set_termios)
-		tty->driver->set_termios(tty, &old);
+	if (tty->ops->set_termios)
+		tty->ops->set_termios(tty, &old);
 	if ((tty->termios->c_cflag & CLOCAL) != bit)
 		ret = -EINVAL;
 	mutex_unlock(&tty->termios_mutex);
@@ -926,8 +951,7 @@ int tty_perform_flush(struct tty_struct *tty, unsigned long arg)
 			ld->flush_buffer(tty);
 		/* fall through */
 	case TCOFLUSH:
-		if (tty->driver->flush_buffer)
-			tty->driver->flush_buffer(tty);
+		tty_driver_flush_buffer(tty);
 		break;
 	default:
 		tty_ldisc_deref(ld);
@@ -984,9 +1008,7 @@ int n_tty_ioctl(struct tty_struct *tty, struct file *file,
 	case TCFLSH:
 		return tty_perform_flush(tty, arg);
 	case TIOCOUTQ:
-		return put_user(tty->driver->chars_in_buffer ?
-				tty->driver->chars_in_buffer(tty) : 0,
-				(int __user *) arg);
+		return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
 	case TIOCINQ:
 		retval = tty->read_cnt;
 		if (L_ICANON(tty))