can: slcan: send the open/close commands to the adapter

In case the bitrate has been set via ip tool, this patch changes the
driver to send the open ("O\r") and close ("C\r) commands to the
adapter.

Link: https://lore.kernel.org/all/20220628163137.413025-9-dario.binacchi@amarulasolutions.comSigned-off-by: NDario Binacchi <dario.binacchi@amarulasolutions.com>
Tested-by: NJeroen Hofstee <jhofstee@victronenergy.com>
Signed-off-by: NMarc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/slcan.c

@@ -435,9 +435,20 @@ static int slcan_transmit_cmd(struct slcan *sl, const unsigned char *cmd)
 static int slc_close(struct net_device *dev)
 {
 	struct slcan *sl = netdev_priv(dev);
+	int err;
 
 	spin_lock_bh(&sl->lock);
 	if (sl->tty) {
+		if (sl->can.bittiming.bitrate &&
+		    sl->can.bittiming.bitrate != CAN_BITRATE_UNKNOWN) {
+			spin_unlock_bh(&sl->lock);
+			err = slcan_transmit_cmd(sl, "C\r");
+			spin_lock_bh(&sl->lock);
+			if (err)
+				netdev_warn(dev,
+					    "failed to send close command 'C\\r'\n");
+		}
+
 		/* TTY discipline is running. */
 		clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
 	}
@@ -496,14 +507,23 @@ static int slc_open(struct net_device *dev)
 			netdev_err(dev,
 				   "failed to send bitrate command 'C\\rS%d\\r'\n",
 				   s);
-			close_candev(dev);
-			return err;
+			goto cmd_transmit_failed;
+		}
+
+		err = slcan_transmit_cmd(sl, "O\r");
+		if (err) {
+			netdev_err(dev, "failed to send open command 'O\\r'\n");
+			goto cmd_transmit_failed;
 		}
 	}
 
 	sl->can.state = CAN_STATE_ERROR_ACTIVE;
 	netif_start_queue(dev);
 	return 0;
+
+cmd_transmit_failed:
+	close_candev(dev);
+	return err;
 }
 
 static void slc_dealloc(struct slcan *sl)