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>

1 files changed, 8 insertions, 7 deletions

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;