can: slcan: extend the protocol with error info

It extends the protocol to receive the adapter CAN communication errors
and forward them to the netdev upper levels.

Link: https://lore.kernel.org/all/20220628163137.413025-12-dario.binacchi@amarulasolutions.com
Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/slcan/slcan-core.c

@@ -175,7 +175,7 @@ int slcan_enable_err_rst_on_open(struct net_device *ndev, bool on)
   ************************************************************************/
 
 /* Send one completely decapsulated can_frame to the network layer */
-static void slc_bump(struct slcan *sl)
+static void slc_bump_frame(struct slcan *sl)
 {
 	struct sk_buff *skb;
 	struct can_frame *cf;
@@ -254,6 +254,144 @@ decode_failed:
 	dev_kfree_skb(skb);
 }
 
+/* An error frame can contain more than one type of error.
+ *
+ * Examples:
+ *
+ * e1a : len 1, errors: ACK error
+ * e3bcO: len 3, errors: Bit0 error, CRC error, Tx overrun error
+ */
+static void slc_bump_err(struct slcan *sl)
+{
+	struct net_device *dev = sl->dev;
+	struct sk_buff *skb;
+	struct can_frame *cf;
+	char *cmd = sl->rbuff;
+	bool rx_errors = false, tx_errors = false, rx_over_errors = false;
+	int i, len;
+
+	/* get len from sanitized ASCII value */
+	len = cmd[1];
+	if (len >= '0' && len < '9')
+		len -= '0';
+	else
+		return;
+
+	if ((len + SLC_CMD_LEN + 1) > sl->rcount)
+		return;
+
+	skb = alloc_can_err_skb(dev, &cf);
+
+	if (skb)
+		cf->can_id |= CAN_ERR_PROT | CAN_ERR_BUSERROR;
+
+	cmd += SLC_CMD_LEN + 1;
+	for (i = 0; i < len; i++, cmd++) {
+		switch (*cmd) {
+		case 'a':
+			netdev_dbg(dev, "ACK error\n");
+			tx_errors = true;
+			if (skb) {
+				cf->can_id |= CAN_ERR_ACK;
+				cf->data[3] = CAN_ERR_PROT_LOC_ACK;
+			}
+
+			break;
+		case 'b':
+			netdev_dbg(dev, "Bit0 error\n");
+			tx_errors = true;
+			if (skb)
+				cf->data[2] |= CAN_ERR_PROT_BIT0;
+
+			break;
+		case 'B':
+			netdev_dbg(dev, "Bit1 error\n");
+			tx_errors = true;
+			if (skb)
+				cf->data[2] |= CAN_ERR_PROT_BIT1;
+
+			break;
+		case 'c':
+			netdev_dbg(dev, "CRC error\n");
+			rx_errors = true;
+			if (skb) {
+				cf->data[2] |= CAN_ERR_PROT_BIT;
+				cf->data[3] = CAN_ERR_PROT_LOC_CRC_SEQ;
+			}
+
+			break;
+		case 'f':
+			netdev_dbg(dev, "Form Error\n");
+			rx_errors = true;
+			if (skb)
+				cf->data[2] |= CAN_ERR_PROT_FORM;
+
+			break;
+		case 'o':
+			netdev_dbg(dev, "Rx overrun error\n");
+			rx_over_errors = true;
+			rx_errors = true;
+			if (skb) {
+				cf->can_id |= CAN_ERR_CRTL;
+				cf->data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
+			}
+
+			break;
+		case 'O':
+			netdev_dbg(dev, "Tx overrun error\n");
+			tx_errors = true;
+			if (skb) {
+				cf->can_id |= CAN_ERR_CRTL;
+				cf->data[1] = CAN_ERR_CRTL_TX_OVERFLOW;
+			}
+
+			break;
+		case 's':
+			netdev_dbg(dev, "Stuff error\n");
+			rx_errors = true;
+			if (skb)
+				cf->data[2] |= CAN_ERR_PROT_STUFF;
+
+			break;
+		default:
+			if (skb)
+				dev_kfree_skb(skb);
+
+			return;
+		}
+	}
+
+	if (rx_errors)
+		dev->stats.rx_errors++;
+
+	if (rx_over_errors)
+		dev->stats.rx_over_errors++;
+
+	if (tx_errors)
+		dev->stats.tx_errors++;
+
+	if (skb)
+		netif_rx(skb);
+}
+
+static void slc_bump(struct slcan *sl)
+{
+	switch (sl->rbuff[0]) {
+	case 'r':
+		fallthrough;
+	case 't':
+		fallthrough;
+	case 'R':
+		fallthrough;
+	case 'T':
+		return slc_bump_frame(sl);
+	case 'e':
+		return slc_bump_err(sl);
+	default:
+		return;
+	}
+}
+
 /* parse tty input stream */
 static void slcan_unesc(struct slcan *sl, unsigned char s)
 {