linux-kernel - [PATCH v4 07/12] can: slcan: set bitrate by CAN device driver API

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Message-Id: <20220614122821.3646071-8-dario.binacchi@amarulasolutions.com>
Date:   Tue, 14 Jun 2022 14:28:16 +0200
From:   Dario Binacchi <dario.binacchi@...rulasolutions.com>
To:     linux-kernel@...r.kernel.org
Cc:     Amarula patchwork <linux-amarula@...rulasolutions.com>,
        Oliver Hartkopp <socketcan@...tkopp.net>,
        michael@...rulasolutions.com,
        Dario Binacchi <dario.binacchi@...rulasolutions.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        Paolo Abeni <pabeni@...hat.com>,
        Wolfgang Grandegger <wg@...ndegger.com>,
        linux-can@...r.kernel.org, netdev@...r.kernel.org
Subject: [PATCH v4 07/12] can: slcan: set bitrate by CAN device driver API

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@...rulasolutions.com>

---

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 2afddaf62586..bd3cf53246c7 100644
--- a/drivers/net/can/slcan.c
+++ b/drivers/net/can/slcan.c
@@ -105,6 +105,11 @@ struct slcan {
 static struct net_device **slcan_devs;
 static DEFINE_SPINLOCK(slcan_lock);
 
+static const u32 slcan_bitrate_const[] = {
+	10000, 20000, 50000, 100000, 125000,
+	250000, 500000, 800000, 1000000
+};
+
  /************************************************************************
   *			SLCAN ENCAPSULATION FORMAT			 *
   ************************************************************************/
@@ -440,6 +445,9 @@ 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);
@@ -451,7 +459,8 @@ 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;
@@ -461,15 +470,39 @@ 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;
 }
@@ -582,6 +615,8 @@ 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