tty: add throttle/unthrottle helpers

Something Arjan suggested which allows us to clean up the code nicely

Signed-off-by: Alan Cox <[e-mail]>
Cc: Arjan van de Ven <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/bluetooth/hci_ldisc.c

···
 	hu->hdev->stat.byte_rx += count;
 	spin_unlock(&hu->rx_lock);
 
-	if (test_and_clear_bit(TTY_THROTTLED, &tty->flags) &&
-					tty->ops->unthrottle)
-		tty->ops->unthrottle(tty);
+	tty_unthrottle(tty);
 }
 
 static int hci_uart_register_dev(struct hci_uart *hu)

drivers/char/n_tty.c

···
 
 static void check_unthrottle(struct tty_struct *tty)
 {
-	if (tty->count &&
-	    test_and_clear_bit(TTY_THROTTLED, &tty->flags) &&
-	    tty->ops->unthrottle)
-		tty->ops->unthrottle(tty);
+	if (tty->count)
+		tty_unthrottle(tty);
 }
 
 /**
···
 	 * mode.  We don't want to throttle the driver if we're in
 	 * canonical mode and don't have a newline yet!
 	 */
-	if (tty->receive_room < TTY_THRESHOLD_THROTTLE) {
-		/* check TTY_THROTTLED first so it indicates our state */
-		if (!test_and_set_bit(TTY_THROTTLED, &tty->flags) &&
-		    tty->ops->throttle)
-			tty->ops->throttle(tty);
-	}
+	if (tty->receive_room < TTY_THRESHOLD_THROTTLE)
+		tty_throttle(tty);
 }
 
 int is_ignored(int sig)

drivers/char/tty_ioctl.c

···
 
 EXPORT_SYMBOL(tty_driver_flush_buffer);
 
+void tty_throttle(struct tty_struct *tty)
+{
+	/* check TTY_THROTTLED first so it indicates our state */
+	if (!test_and_set_bit(TTY_THROTTLED, &tty->flags) &&
+	    tty->ops->throttle)
+		tty->ops->throttle(tty);
+}
+EXPORT_SYMBOL(tty_throttle);
+
+void tty_unthrottle(struct tty_struct *tty)
+{
+	if (test_and_clear_bit(TTY_THROTTLED, &tty->flags) &&
+	    tty->ops->unthrottle)
+		tty->ops->unthrottle(tty);
+}
+EXPORT_SYMBOL(tty_unthrottle);
 
 /**
  *	tty_wait_until_sent	-	wait for I/O to finish

drivers/net/hamradio/6pack.c

···
 	sixpack_decode(sp, buf, count1);
 
 	sp_put(sp);
-	if (test_and_clear_bit(TTY_THROTTLED, &tty->flags)
-	    && tty->ops->unthrottle)
-		tty->ops->unthrottle(tty);
+	tty_unthrottle(tty);
 }
 
 /*

drivers/net/hamradio/mkiss.c

···
 	}
 
 	mkiss_put(ax);
-	if (test_and_clear_bit(TTY_THROTTLED, &tty->flags)
-	    && tty->ops->unthrottle)
-		tty->ops->unthrottle(tty);
+	tty_unthrottle(tty);
 }
 
 /*

drivers/net/ppp_async.c

···
 	if (!skb_queue_empty(&ap->rqueue))
 		tasklet_schedule(&ap->tsk);
 	ap_put(ap);
-	if (test_and_clear_bit(TTY_THROTTLED, &tty->flags)
-	    && tty->ops->unthrottle)
-		tty->ops->unthrottle(tty);
+	tty_unthrottle(tty);
 }
 
 static void

drivers/net/ppp_synctty.c

···
 	if (!skb_queue_empty(&ap->rqueue))
 		tasklet_schedule(&ap->tsk);
 	sp_put(ap);
-	if (test_and_clear_bit(TTY_THROTTLED, &tty->flags)
-	    && tty->ops->unthrottle)
-		tty->ops->unthrottle(tty);
+	tty_unthrottle(tty);
 }
 
 static void

include/linux/tty.h

···
 extern int tty_chars_in_buffer(struct tty_struct *tty);
 extern int tty_write_room(struct tty_struct *tty);
 extern void tty_driver_flush_buffer(struct tty_struct *tty);
+extern void tty_throttle(struct tty_struct *tty);
+extern void tty_unthrottle(struct tty_struct *tty);
 
 extern int is_current_pgrp_orphaned(void);
 extern struct pid *tty_get_pgrp(struct tty_struct *tty);

include/linux/tty_driver.h

···
  * 	This routine notifies the tty driver that input buffers for
  * 	the line discipline are close to full, and it should somehow
  * 	signal that no more characters should be sent to the tty.
+ *
+ *	Optional: Always invoke via tty_throttle();
  * 
  * void (*unthrottle)(struct tty_struct * tty);
  *
···
  * 	that characters can now be sent to the tty without fear of
  * 	overrunning the input buffers of the line disciplines.
  * 
+ *	Optional: Always invoke via tty_unthrottle();
+ *
  * void (*stop)(struct tty_struct *tty);
  *
  * 	This routine notifies the tty driver that it should stop