netdev - [PATCH v2 07/13] can: slcan: set bitrate by CAN device driver API

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Message-Id: <20220608165116.1575390-8-dario.binacchi@amarulasolutions.com>
Date:   Wed,  8 Jun 2022 18:51:10 +0200
From:   Dario Binacchi <dario.binacchi@...rulasolutions.com>
To:     linux-kernel@...r.kernel.org
Cc:     Amarula patchwork <linux-amarula@...rulasolutions.com>,
        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 v2 07/13] 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 v2:
- Use the CAN framework support for setting fixed bit rates.

 drivers/net/can/slcan.c | 39 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 38 insertions(+), 1 deletion(-)

diff --git a/drivers/net/can/slcan.c b/drivers/net/can/slcan.c
index cab0a2a8c84c..8561bcee81ba 100644
--- a/drivers/net/can/slcan.c
+++ b/drivers/net/can/slcan.c
@@ -439,6 +439,7 @@ static int slc_close(struct net_device *dev)
 	netif_stop_queue(dev);
 	close_candev(dev);
 	sl->can.state = CAN_STATE_STOPPED;
+	sl->can.bittiming.bitrate = 0;
 	sl->rcount   = 0;
 	sl->xleft    = 0;
 	spin_unlock_bh(&sl->lock);
@@ -460,7 +461,9 @@ static int slc_open(struct net_device *dev)
 	 * can.bittiming.bitrate is 0, causing open_candev() to fail.
 	 * So let's set to a fake value.
 	 */
-	sl->can.bittiming.bitrate = -1;
+	if (sl->can.bittiming.bitrate == 0)
+		sl->can.bittiming.bitrate = -1UL;
+
 	err = open_candev(dev);
 	if (err) {
 		netdev_err(dev, "failed to open can device\n");
@@ -558,6 +561,37 @@ static void slc_sync(void)
 	}
 }
 
+static const u32 slcan_bitrate_const[] = {
+	10000, 20000, 50000, 100000, 125000,
+	250000, 500000, 800000, 1000000
+};
+
+static int slc_do_set_bittiming(struct net_device *dev)
+{
+	struct slcan *sl = netdev_priv(dev);
+	unsigned char cmd[SLC_MTU];
+	int s, err;
+
+	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) {
+		sl->can.bittiming.bitrate = 0;
+		netdev_err(sl->dev,
+			   "failed to send bitrate command 'C\\rS%d\\r'\n", s);
+	}
+
+	return err;
+}
+
 /* Find a free SLCAN channel, and link in this `tty' line. */
 static struct slcan *slc_alloc(void)
 {
@@ -587,6 +621,9 @@ 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);
+	sl->can.do_set_bittiming = slc_do_set_bittiming;
 	spin_lock_init(&sl->lock);
 	INIT_WORK(&sl->tx_work, slcan_transmit);
 	init_waitqueue_head(&sl->xcmd_wait);
-- 
2.32.0