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>

2 files changed, 27 insertions, 24 deletions

diff --git a/drivers/net/hamradio/6pack.c b/drivers/net/hamradio/6pack.c
index 1da55dd2a5a0..82a36266dfc9 100644
--- a/drivers/net/hamradio/6pack.c
+++ b/drivers/net/hamradio/6pack.c
@@ -148,13 +148,13 @@ static void sp_xmit_on_air(unsigned long channel)
 
 	if (((sp->status1 & SIXP_DCD_MASK) == 0) && (random < sp->persistence)) {
 		sp->led_state = 0x70;
-		sp->tty->driver->write(sp->tty, &sp->led_state, 1);
+		sp->tty->ops->write(sp->tty, &sp->led_state, 1);
 		sp->tx_enable = 1;
-		actual = sp->tty->driver->write(sp->tty, sp->xbuff, sp->status2);
+		actual = sp->tty->ops->write(sp->tty, sp->xbuff, sp->status2);
 		sp->xleft -= actual;
 		sp->xhead += actual;
 		sp->led_state = 0x60;
-		sp->tty->driver->write(sp->tty, &sp->led_state, 1);
+		sp->tty->ops->write(sp->tty, &sp->led_state, 1);
 		sp->status2 = 0;
 	} else
 		mod_timer(&sp->tx_t, jiffies + ((when + 1) * HZ) / 100);
@@ -220,13 +220,13 @@ static void sp_encaps(struct sixpack *sp, unsigned char *icp, int len)
 	 */
 	if (sp->duplex == 1) {
 		sp->led_state = 0x70;
-		sp->tty->driver->write(sp->tty, &sp->led_state, 1);
+		sp->tty->ops->write(sp->tty, &sp->led_state, 1);
 		sp->tx_enable = 1;
-		actual = sp->tty->driver->write(sp->tty, sp->xbuff, count);
+		actual = sp->tty->ops->write(sp->tty, sp->xbuff, count);
 		sp->xleft = count - actual;
 		sp->xhead = sp->xbuff + actual;
 		sp->led_state = 0x60;
-		sp->tty->driver->write(sp->tty, &sp->led_state, 1);
+		sp->tty->ops->write(sp->tty, &sp->led_state, 1);
 	} else {
 		sp->xleft = count;
 		sp->xhead = sp->xbuff;
@@ -444,7 +444,7 @@ static void sixpack_write_wakeup(struct tty_struct *tty)
 	}
 
 	if (sp->tx_enable) {
-		actual = tty->driver->write(tty, sp->xhead, sp->xleft);
+		actual = tty->ops->write(tty, sp->xhead, sp->xleft);
 		sp->xleft -= actual;
 		sp->xhead += actual;
 	}
@@ -492,8 +492,8 @@ static void sixpack_receive_buf(struct tty_struct *tty,
 
 	sp_put(sp);
 	if (test_and_clear_bit(TTY_THROTTLED, &tty->flags)
-	    && tty->driver->unthrottle)
-		tty->driver->unthrottle(tty);
+	    && tty->ops->unthrottle)
+		tty->ops->unthrottle(tty);
 }
 
 /*
@@ -554,8 +554,8 @@ static void resync_tnc(unsigned long channel)
 	/* resync the TNC */
 
 	sp->led_state = 0x60;
-	sp->tty->driver->write(sp->tty, &sp->led_state, 1);
-	sp->tty->driver->write(sp->tty, &resync_cmd, 1);
+	sp->tty->ops->write(sp->tty, &sp->led_state, 1);
+	sp->tty->ops->write(sp->tty, &resync_cmd, 1);
 
 
 	/* Start resync timer again -- the TNC might be still absent */
@@ -573,7 +573,7 @@ static inline int tnc_init(struct sixpack *sp)
 
 	tnc_set_sync_state(sp, TNC_UNSYNC_STARTUP);
 
-	sp->tty->driver->write(sp->tty, &inbyte, 1);
+	sp->tty->ops->write(sp->tty, &inbyte, 1);
 
 	del_timer(&sp->resync_t);
 	sp->resync_t.data = (unsigned long) sp;
@@ -601,6 +601,8 @@ static int sixpack_open(struct tty_struct *tty)
 
 	if (!capable(CAP_NET_ADMIN))
 		return -EPERM;
+	if (tty->ops->write == NULL)
+		return -EOPNOTSUPP;
 
 	dev = alloc_netdev(sizeof(struct sixpack), "sp%d", sp_setup);
 	if (!dev) {
@@ -914,9 +916,9 @@ static void decode_prio_command(struct sixpack *sp, unsigned char cmd)
 	} else { /* output watchdog char if idle */
 		if ((sp->status2 != 0) && (sp->duplex == 1)) {
 			sp->led_state = 0x70;
-			sp->tty->driver->write(sp->tty, &sp->led_state, 1);
+			sp->tty->ops->write(sp->tty, &sp->led_state, 1);
 			sp->tx_enable = 1;
-			actual = sp->tty->driver->write(sp->tty, sp->xbuff, sp->status2);
+			actual = sp->tty->ops->write(sp->tty, sp->xbuff, sp->status2);
 			sp->xleft -= actual;
 			sp->xhead += actual;
 			sp->led_state = 0x60;
@@ -926,7 +928,7 @@ static void decode_prio_command(struct sixpack *sp, unsigned char cmd)
 	}
 
 	/* needed to trigger the TNC watchdog */
-	sp->tty->driver->write(sp->tty, &sp->led_state, 1);
+	sp->tty->ops->write(sp->tty, &sp->led_state, 1);
 
         /* if the state byte has been received, the TNC is present,
            so the resync timer can be reset. */
@@ -956,12 +958,12 @@ static void decode_std_command(struct sixpack *sp, unsigned char cmd)
 			if ((sp->status & SIXP_RX_DCD_MASK) ==
 				SIXP_RX_DCD_MASK) {
 				sp->led_state = 0x68;
-				sp->tty->driver->write(sp->tty, &sp->led_state, 1);
+				sp->tty->ops->write(sp->tty, &sp->led_state, 1);
 			}
 		} else {
 			sp->led_state = 0x60;
 			/* fill trailing bytes with zeroes */
-			sp->tty->driver->write(sp->tty, &sp->led_state, 1);
+			sp->tty->ops->write(sp->tty, &sp->led_state, 1);
 			rest = sp->rx_count;
 			if (rest != 0)
 				 for (i = rest; i <= 3; i++)
diff --git a/drivers/net/hamradio/mkiss.c b/drivers/net/hamradio/mkiss.c
index 30c9b3b0d131..ebcc5adee7cc 100644
--- a/drivers/net/hamradio/mkiss.c
+++ b/drivers/net/hamradio/mkiss.c
@@ -516,7 +516,7 @@ static void ax_encaps(struct net_device *dev, unsigned char *icp, int len)
 	spin_unlock_bh(&ax->buflock);
 
 	set_bit(TTY_DO_WRITE_WAKEUP, &ax->tty->flags);
-	actual = ax->tty->driver->write(ax->tty, ax->xbuff, count);
+	actual = ax->tty->ops->write(ax->tty, ax->xbuff, count);
 	ax->stats.tx_packets++;
 	ax->stats.tx_bytes += actual;
 
@@ -546,7 +546,7 @@ static int ax_xmit(struct sk_buff *skb, struct net_device *dev)
 		}
 
 		printk(KERN_ERR "mkiss: %s: transmit timed out, %s?\n", dev->name,
-		       (ax->tty->driver->chars_in_buffer(ax->tty) || ax->xleft) ?
+		       (ax->tty->ops->chars_in_buffer(ax->tty) || ax->xleft) ?
 		       "bad line quality" : "driver error");
 
 		ax->xleft = 0;
@@ -736,6 +736,8 @@ static int mkiss_open(struct tty_struct *tty)
 
 	if (!capable(CAP_NET_ADMIN))
 		return -EPERM;
+	if (tty->ops->write == NULL)
+		return -EOPNOTSUPP;
 
 	dev = alloc_netdev(sizeof(struct mkiss), "ax%d", ax_setup);
 	if (!dev) {
@@ -754,8 +756,7 @@ static int mkiss_open(struct tty_struct *tty)
 	tty->disc_data = ax;
 	tty->receive_room = 65535;
 
-	if (tty->driver->flush_buffer)
-		tty->driver->flush_buffer(tty);
+	tty_driver_flush_buffer(tty);
 
 	/* Restore default settings */
 	dev->type = ARPHRD_AX25;
@@ -936,8 +937,8 @@ static void mkiss_receive_buf(struct tty_struct *tty, const unsigned char *cp,
 
 	mkiss_put(ax);
 	if (test_and_clear_bit(TTY_THROTTLED, &tty->flags)
-	    && tty->driver->unthrottle)
-		tty->driver->unthrottle(tty);
+	    && tty->ops->unthrottle)
+		tty->ops->unthrottle(tty);
 }
 
 /*
@@ -962,7 +963,7 @@ static void mkiss_write_wakeup(struct tty_struct *tty)
 		goto out;
 	}
 
-	actual = tty->driver->write(tty, ax->xhead, ax->xleft);
+	actual = tty->ops->write(tty, ax->xhead, ax->xleft);
 	ax->xleft -= actual;
 	ax->xhead += actual;