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, 5 deletions

diff --git a/drivers/net/slip.c b/drivers/net/slip.c
index 5a55ede352f4..84af68fdb6c2 100644
--- a/drivers/net/slip.c
+++ b/drivers/net/slip.c
@@ -396,14 +396,14 @@ static void sl_encaps(struct slip *sl, unsigned char *icp, int len)
 
         /* Order of next two lines is *very* important.
          * When we are sending a little amount of data,
-         * the transfer may be completed inside driver.write()
+         * the transfer may be completed inside the ops->write()
          * routine, because it's running with interrupts enabled.
          * In this case we *never* got WRITE_WAKEUP event,
          * if we did not request it before write operation.
          *       14 Oct 1994  Dmitry Gorodchanin.
          */
         sl->tty->flags |= (1 << TTY_DO_WRITE_WAKEUP);
-        actual = sl->tty->driver->write(sl->tty, sl->xbuff, count);
+        actual = sl->tty->ops->write(sl->tty, sl->xbuff, count);
 #ifdef SL_CHECK_TRANSMIT
         sl->dev->trans_start = jiffies;
 #endif
@@ -437,7 +437,7 @@ static void slip_write_wakeup(struct tty_struct *tty)
                 return;
         }
 
-        actual = tty->driver->write(tty, sl->xhead, sl->xleft);
+        actual = tty->ops->write(tty, sl->xhead, sl->xleft);
         sl->xleft -= actual;
         sl->xhead += actual;
 }
@@ -462,7 +462,7 @@ static void sl_tx_timeout(struct net_device *dev)
                 }
                 printk(KERN_WARNING "%s: transmit timed out, %s?\n",
                         dev->name,
-                        (sl->tty->driver->chars_in_buffer(sl->tty) || sl->xleft) ?
+                        (tty_chars_in_buffer(sl->tty) || sl->xleft) ?
                                 "bad line quality" : "driver error");
                 sl->xleft = 0;
                 sl->tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
@@ -830,6 +830,9 @@ static int slip_open(struct tty_struct *tty)
         if (!capable(CAP_NET_ADMIN))
                 return -EPERM;
 
+        if (tty->ops->write == NULL)
+                return -EOPNOTSUPP;
+
         /* RTnetlink lock is misused here to serialize concurrent
            opens of slip channels. There are better ways, but it is
            the simplest one.
@@ -1432,7 +1435,7 @@ static void sl_outfill(unsigned long sls)
                         /* put END into tty queue. Is it right ??? */
                         if (!netif_queue_stopped(sl->dev)) {
                                 /* if device busy no outfill */
-                                sl->tty->driver->write(sl->tty, &s, 1);
+                                sl->tty->ops->write(sl->tty, &s, 1);
                         }
                 } else
                         set_bit(SLF_OUTWAIT, &sl->flags);