Merge branch 'mctp-serial-minor-fixes'

Jeremy Kerr says:

====================
mctp serial minor fixes

We had a few minor fixes queued for a v4 of the original series, so
they're sent here as separate changes.

v2:
 - fix ordering of cancel_work vs. unregister_netdev.
====================

Link: https://lore.kernel.org/r/20211125060739.3023442-1-jk@codeconstruct.com.au
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/mctp/mctp-serial.c

@@ -410,7 +410,14 @@ static const struct net_device_ops mctp_serial_netdev_ops = {
 static void mctp_serial_setup(struct net_device *ndev)
 {
 	ndev->type = ARPHRD_MCTP;
+
+	/* we limit at the fixed MTU, which is also the MCTP-standard
+	 * baseline MTU, so is also our minimum
+	 */
 	ndev->mtu = MCTP_SERIAL_MTU;
+	ndev->max_mtu = MCTP_SERIAL_MTU;
+	ndev->min_mtu = MCTP_SERIAL_MTU;
+
 	ndev->hard_header_len = 0;
 	ndev->addr_len = 0;
 	ndev->tx_queue_len = DEFAULT_TX_QUEUE_LEN;
@@ -432,9 +439,6 @@ static int mctp_serial_open(struct tty_struct *tty)
 	if (!tty->ops->write)
 		return -EOPNOTSUPP;
 
-	if (tty->disc_data)
-		return -EEXIST;
-
 	idx = ida_alloc(&mctp_serial_ida, GFP_KERNEL);
 	if (idx < 0)
 		return idx;
@@ -479,6 +483,7 @@ static void mctp_serial_close(struct tty_struct *tty)
 	int idx = dev->idx;
 
 	unregister_netdev(dev->netdev);
+	cancel_work_sync(&dev->tx_work);
 	ida_free(&mctp_serial_ida, idx);
 }