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, 2 insertions, 2 deletions

diff --git a/kernel/printk.c b/kernel/printk.c
index d3f9c0f788bf..0d232589a923 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -1272,8 +1272,8 @@ late_initcall(disable_boot_consoles);
  */
 void tty_write_message(struct tty_struct *tty, char *msg)
 {
-        if (tty && tty->driver->write)
-                tty->driver->write(tty, msg, strlen(msg));
+        if (tty && tty->ops->write)
+                tty->ops->write(tty, msg, strlen(msg));
         return;
 }