[PATCH v5 07/12] can: slcan: set bitrate by CAN device driver API

[Dario Binacchi <dario.binacchi@amarulasolutions.com>]

It allows to set the bitrate via ip tool, as it happens for the other
CAN device drivers. It still remains possible to set the bitrate via
slcand or slcan_attach utilities. In case the ip tool is used, the
driver will send the serial command to the adapter.

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

---

(no changes since v4)

Changes in v4:
- Use CAN_BITRATE_UNSET (0) and CAN_BITRATE_UNKNOWN (-1U) macros.
- Don't reset the bitrate in ndo_stop() if it has been configured.

Changes in v3:
- Remove the slc_do_set_bittiming().
- Set the bitrate in the ndo_open().
- Replace -1UL with -1U in setting a fake value for the bitrate.

Changes in v2:
- Use the CAN framework support for setting fixed bit rates.

 drivers/net/can/slcan.c | 41 ++++++++++++++++++++++++++++++++++++++---
 1 file changed, 38 insertions(+), 3 deletions(-)

diff --git a/drivers/net/can/slcan.c b/drivers/net/can/slcan.c
index dfccf8d6c9a5..74033e2d7097 100644
--- a/drivers/net/can/slcan.c
+++ b/drivers/net/can/slcan.c
@@ -104,6 +104,11 @@ struct slcan {
 
 static struct net_device **slcan_devs;
 
+static const u32 slcan_bitrate_const[] = {
+	10000, 20000, 50000, 100000, 125000,
+	250000, 500000, 800000, 1000000
+};
+
  /************************************************************************
   *			SLCAN ENCAPSULATION FORMAT			 *
   ************************************************************************/
@@ -439,6 +444,9 @@ static int slc_close(struct net_device *dev)
 	netif_stop_queue(dev);
 	close_candev(dev);
 	sl->can.state = CAN_STATE_STOPPED;
+	if (sl->can.bittiming.bitrate == CAN_BITRATE_UNKNOWN)
+		sl->can.bittiming.bitrate = CAN_BITRATE_UNSET;
+
 	sl->rcount   = 0;
 	sl->xleft    = 0;
 	spin_unlock_bh(&sl->lock);
@@ -450,7 +458,8 @@ static int slc_close(struct net_device *dev)
 static int slc_open(struct net_device *dev)
 {
 	struct slcan *sl = netdev_priv(dev);
-	int err;
+	unsigned char cmd[SLC_MTU];
+	int err, s;
 
 	if (sl->tty == NULL)
 		return -ENODEV;
@@ -460,15 +469,39 @@ static int slc_open(struct net_device *dev)
 	 * can.bittiming.bitrate is CAN_BITRATE_UNSET (0), causing
 	 * open_candev() to fail. So let's set to a fake value.
 	 */
-	sl->can.bittiming.bitrate = CAN_BITRATE_UNKNOWN;
+	if (sl->can.bittiming.bitrate == CAN_BITRATE_UNSET)
+		sl->can.bittiming.bitrate = CAN_BITRATE_UNKNOWN;
+
 	err = open_candev(dev);
 	if (err) {
 		netdev_err(dev, "failed to open can device\n");
 		return err;
 	}
 
-	sl->can.state = CAN_STATE_ERROR_ACTIVE;
 	sl->flags &= BIT(SLF_INUSE);
+
+	if (sl->can.bittiming.bitrate != CAN_BITRATE_UNKNOWN) {
+		for (s = 0; s < ARRAY_SIZE(slcan_bitrate_const); s++) {
+			if (sl->can.bittiming.bitrate == slcan_bitrate_const[s])
+				break;
+		}
+
+		/* The CAN framework has already validate the bitrate value,
+		 * so we can avoid to check if `s' has been properly set.
+		 */
+
+		snprintf(cmd, sizeof(cmd), "C\rS%d\r", s);
+		err = slcan_transmit_cmd(sl, cmd);
+		if (err) {
+			netdev_err(dev,
+				   "failed to send bitrate command 'C\\rS%d\\r'\n",
+				   s);
+			close_candev(dev);
+			return err;
+		}
+	}
+
+	sl->can.state = CAN_STATE_ERROR_ACTIVE;
 	netif_start_queue(dev);
 	return 0;
 }
@@ -581,6 +614,8 @@ static struct slcan *slc_alloc(void)
 	/* Initialize channel control data */
 	sl->magic = SLCAN_MAGIC;
 	sl->dev	= dev;
+	sl->can.bitrate_const = slcan_bitrate_const;
+	sl->can.bitrate_const_cnt = ARRAY_SIZE(slcan_bitrate_const);
 	spin_lock_init(&sl->lock);
 	INIT_WORK(&sl->tx_work, slcan_transmit);
 	init_waitqueue_head(&sl->xcmd_wait);
-- 
2.32.0