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, 4 deletions

diff --git a/arch/ia64/hp/sim/simserial.c b/arch/ia64/hp/sim/simserial.c
index eb0c32a85fd7..23cafc80d2a4 100644
--- a/arch/ia64/hp/sim/simserial.c
+++ b/arch/ia64/hp/sim/simserial.c
@@ -210,21 +210,23 @@ static void do_softint(struct work_struct *private_)
 	printk(KERN_ERR "simserial: do_softint called\n");
 }
 
-static void rs_put_char(struct tty_struct *tty, unsigned char ch)
+static int rs_put_char(struct tty_struct *tty, unsigned char ch)
 {
 	struct async_struct *info = (struct async_struct *)tty->driver_data;
 	unsigned long flags;
 
-	if (!tty || !info->xmit.buf) return;
+	if (!tty || !info->xmit.buf)
+		return 0;
 
 	local_irq_save(flags);
 	if (CIRC_SPACE(info->xmit.head, info->xmit.tail, SERIAL_XMIT_SIZE) == 0) {
 		local_irq_restore(flags);
-		return;
+		return 0;
 	}
 	info->xmit.buf[info->xmit.head] = ch;
 	info->xmit.head = (info->xmit.head + 1) & (SERIAL_XMIT_SIZE-1);
 	local_irq_restore(flags);
+	return 1;
 }
 
 static void transmit_chars(struct async_struct *info, int *intr_done)
@@ -621,7 +623,8 @@ static void rs_close(struct tty_struct *tty, struct file * filp)
 	 * the line discipline to only process XON/XOFF characters.
 	 */
 	shutdown(info);
-	if (tty->driver->flush_buffer) tty->driver->flush_buffer(tty);
+	if (tty->ops->flush_buffer)
+		tty->ops->flush_buffer(tty);
 	if (tty->ldisc.flush_buffer) tty->ldisc.flush_buffer(tty);
 	info->event = 0;
 	info->tty = NULL;