tty: usb-serial krefs

Use kref in the USB serial drivers so that we don't free tty structures
from under the URB receive handlers as has historically been the case if
you were unlucky. This also gives us a framework for general tty drivers to
use tty_port objects and refcount.

Contains two err->dev_err changes merged together to fix clashes in the
-next tree.

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/drivers/usb/serial/mct_u232.c b/drivers/usb/serial/mct_u232.c
index 0ded8bd6ec8..9b2cef81cde 100644
--- a/drivers/usb/serial/mct_u232.c
+++ b/drivers/usb/serial/mct_u232.c
@@ -563,10 +563,11 @@ static void mct_u232_read_int_callback(struct urb *urb)
 	 * Work-a-round: handle the 'usual' bulk-in pipe here
 	 */
 	if (urb->transfer_buffer_length > 2) {
-		tty = port->port.tty;
+		tty = tty_port_tty_get(&port->port);
 		if (urb->actual_length) {
 			tty_insert_flip_string(tty, data, urb->actual_length);
 			tty_flip_buffer_push(tty);
+			tty_kref_put(tty);
 		}
 		goto exit;
 	}
@@ -591,7 +592,7 @@ static void mct_u232_read_int_callback(struct urb *urb)
 	 * to look in to this before committing any code.
 	 */
 	if (priv->last_lsr & MCT_U232_LSR_ERR) {
-		tty = port->port.tty;
+		tty = tty_port_tty_get(&port->port);
 		/* Overrun Error */
 		if (priv->last_lsr & MCT_U232_LSR_OE) {
 		}
@@ -604,6 +605,7 @@ static void mct_u232_read_int_callback(struct urb *urb)
 		/* Break Indicator */
 		if (priv->last_lsr & MCT_U232_LSR_BI) {
 		}
+		tty_kref_put(tty);
 	}
 #endif
 	spin_unlock_irqrestore(&priv->lock, flags);