can: slcan: use the alloc_can_skb() helper

It is used successfully by most (if not all) CAN device drivers. It
allows to remove replicated code.

Link: https://lore.kernel.org/all/20220628163137.413025-4-dario.binacchi@amarulasolutions.com
Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Tested-by: Jeroen Hofstee <jhofstee@victronenergy.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/slcan.c

@@ -54,6 +54,7 @@
 #include <linux/kernel.h>
 #include <linux/workqueue.h>
 #include <linux/can.h>
+#include <linux/can/dev.h>
 #include <linux/can/skb.h>
 #include <linux/can/can-ml.h>
 
@@ -143,85 +144,80 @@ static struct net_device **slcan_devs;
 static void slc_bump(struct slcan *sl)
 {
 	struct sk_buff *skb;
-	struct can_frame cf;
+	struct can_frame *cf;
 	int i, tmp;
 	u32 tmpid;
 	char *cmd = sl->rbuff;
 
-	memset(&cf, 0, sizeof(cf));
+	skb = alloc_can_skb(sl->dev, &cf);
+	if (unlikely(!skb)) {
+		sl->dev->stats.rx_dropped++;
+		return;
+	}
 
 	switch (*cmd) {
 	case 'r':
-		cf.can_id = CAN_RTR_FLAG;
+		cf->can_id = CAN_RTR_FLAG;
 		fallthrough;
 	case 't':
 		/* store dlc ASCII value and terminate SFF CAN ID string */
-		cf.len = sl->rbuff[SLC_CMD_LEN + SLC_SFF_ID_LEN];
+		cf->len = sl->rbuff[SLC_CMD_LEN + SLC_SFF_ID_LEN];
 		sl->rbuff[SLC_CMD_LEN + SLC_SFF_ID_LEN] = 0;
 		/* point to payload data behind the dlc */
 		cmd += SLC_CMD_LEN + SLC_SFF_ID_LEN + 1;
 		break;
 	case 'R':
-		cf.can_id = CAN_RTR_FLAG;
+		cf->can_id = CAN_RTR_FLAG;
 		fallthrough;
 	case 'T':
-		cf.can_id |= CAN_EFF_FLAG;
+		cf->can_id |= CAN_EFF_FLAG;
 		/* store dlc ASCII value and terminate EFF CAN ID string */
-		cf.len = sl->rbuff[SLC_CMD_LEN + SLC_EFF_ID_LEN];
+		cf->len = sl->rbuff[SLC_CMD_LEN + SLC_EFF_ID_LEN];
 		sl->rbuff[SLC_CMD_LEN + SLC_EFF_ID_LEN] = 0;
 		/* point to payload data behind the dlc */
 		cmd += SLC_CMD_LEN + SLC_EFF_ID_LEN + 1;
 		break;
 	default:
-		return;
+		goto decode_failed;
 	}
 
 	if (kstrtou32(sl->rbuff + SLC_CMD_LEN, 16, &tmpid))
-		return;
+		goto decode_failed;
 
-	cf.can_id |= tmpid;
+	cf->can_id |= tmpid;
 
 	/* get len from sanitized ASCII value */
-	if (cf.len >= '0' && cf.len < '9')
-		cf.len -= '0';
+	if (cf->len >= '0' && cf->len < '9')
+		cf->len -= '0';
 	else
-		return;
+		goto decode_failed;
 
 	/* RTR frames may have a dlc > 0 but they never have any data bytes */
-	if (!(cf.can_id & CAN_RTR_FLAG)) {
-		for (i = 0; i < cf.len; i++) {
+	if (!(cf->can_id & CAN_RTR_FLAG)) {
+		for (i = 0; i < cf->len; i++) {
 			tmp = hex_to_bin(*cmd++);
 			if (tmp < 0)
-				return;
-			cf.data[i] = (tmp << 4);
+				goto decode_failed;
+
+			cf->data[i] = (tmp << 4);
 			tmp = hex_to_bin(*cmd++);
 			if (tmp < 0)
-				return;
-			cf.data[i] |= tmp;
+				goto decode_failed;
+
+			cf->data[i] |= tmp;
 		}
 	}
 
-	skb = dev_alloc_skb(sizeof(struct can_frame) +
-			    sizeof(struct can_skb_priv));
-	if (!skb)
-		return;
-
-	skb->dev = sl->dev;
-	skb->protocol = htons(ETH_P_CAN);
-	skb->pkt_type = PACKET_BROADCAST;
-	skb->ip_summed = CHECKSUM_UNNECESSARY;
-
-	can_skb_reserve(skb);
-	can_skb_prv(skb)->ifindex = sl->dev->ifindex;
-	can_skb_prv(skb)->skbcnt = 0;
-
-	skb_put_data(skb, &cf, sizeof(struct can_frame));
-
 	sl->dev->stats.rx_packets++;
-	if (!(cf.can_id & CAN_RTR_FLAG))
-		sl->dev->stats.rx_bytes += cf.len;
+	if (!(cf->can_id & CAN_RTR_FLAG))
+		sl->dev->stats.rx_bytes += cf->len;
 
 	netif_rx(skb);
+	return;
+
+decode_failed:
+	sl->dev->stats.rx_errors++;
+	dev_kfree_skb(skb);
 }
 
 /* parse tty input stream */