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, 7 insertions, 10 deletions

diff --git a/drivers/char/n_r3964.c b/drivers/char/n_r3964.c
index 3f6486e9f1ec..902169062332 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);