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, 7 deletions

diff --git a/drivers/char/isicom.c b/drivers/char/isicom.c
index 57b115272aaa..9c6be8da220c 100644
--- a/drivers/char/isicom.c
+++ b/drivers/char/isicom.c
@@ -1140,28 +1140,29 @@ static int isicom_write(struct tty_struct *tty,	const unsigned char *buf,
 }
 
 /* put_char et all */
-static void isicom_put_char(struct tty_struct *tty, unsigned char ch)
+static int isicom_put_char(struct tty_struct *tty, unsigned char ch)
 {
         struct isi_port *port = tty->driver_data;
         struct isi_board *card = port->card;
         unsigned long flags;
 
         if (isicom_paranoia_check(port, tty->name, "isicom_put_char"))
-                return;
+                return 0;
 
         if (!port->xmit_buf)
-                return;
+                return 0;
 
         spin_lock_irqsave(&card->card_lock, flags);
-        if (port->xmit_cnt >= SERIAL_XMIT_SIZE - 1)
-                goto out;
+        if (port->xmit_cnt >= SERIAL_XMIT_SIZE - 1) {
+                spin_unlock_irqrestore(&card->card_lock, flags);
+                return 0;
+        }
 
         port->xmit_buf[port->xmit_head++] = ch;
         port->xmit_head &= (SERIAL_XMIT_SIZE - 1);
         port->xmit_cnt++;
         spin_unlock_irqrestore(&card->card_lock, flags);
-out:
-        return;
+        return 1;
 }
 
 /* flush_chars et all */