For non-legacy, i.e. ip based configuration, add support for listen-only
mode. If listen-only is requested send a listen-only ("L\r") command
instead of an open ("O\r") command to the adapter.

Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>

---

Changes in v2:
- Remove comment on listen-only command.
- Update the commit subject and description.

 drivers/net/can/slcan/slcan-core.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/drivers/net/can/slcan/slcan-core.c b/drivers/net/can/slcan/slcan-core.c
index 919311890d2c..76f20dc1aa90 100644
--- a/drivers/net/can/slcan/slcan-core.c
+++ b/drivers/net/can/slcan/slcan-core.c
@@ -724,10 +724,20 @@ static int slcan_netdev_open(struct net_device *dev)
 			}
 		}
 
-		err = slcan_transmit_cmd(sl, "O\r");
-		if (err) {
-			netdev_err(dev, "failed to send open command 'O\\r'\n");
-			goto cmd_transmit_failed;
+		if (sl->can.ctrlmode & CAN_CTRLMODE_LISTENONLY) {
+			err = slcan_transmit_cmd(sl, "L\r");
+			if (err) {
+				netdev_err(dev,
+					   "failed to send listen-only command 'L\\r'\n");
+				goto cmd_transmit_failed;
+			}
+		} else {
+			err = slcan_transmit_cmd(sl, "O\r");
+			if (err) {
+				netdev_err(dev,
+					   "failed to send open command 'O\\r'\n");
+				goto cmd_transmit_failed;
+			}
 		}
 	}
 
@@ -814,6 +824,7 @@ static int slcan_open(struct tty_struct *tty)
 	/* Configure CAN metadata */
 	sl->can.bitrate_const = slcan_bitrate_const;
 	sl->can.bitrate_const_cnt = ARRAY_SIZE(slcan_bitrate_const);
+	sl->can.ctrlmode_supported = CAN_CTRLMODE_LISTENONLY;
 
 	/* Configure netdev interface */
 	sl->dev	= dev;
-- 
2.32.0