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>

fs/proc/proc_tty.c

@@ -192,16 +192,14 @@ void proc_tty_register_driver(struct tty_driver *driver)
 {
 	struct proc_dir_entry *ent;
 		
-	if ((!driver->read_proc && !driver->write_proc) ||
-	    !driver->driver_name ||
+	if (!driver->ops->read_proc || !driver->driver_name ||
 	    driver->proc_entry)
 		return;
 
 	ent = create_proc_entry(driver->driver_name, 0, proc_tty_driver);
 	if (!ent)
 		return;
-	ent->read_proc = driver->read_proc;
-	ent->write_proc = driver->write_proc;
+	ent->read_proc = driver->ops->read_proc;
 	ent->owner = driver->owner;
 	ent->data = driver;