can: dev: let can_get_echo_skb() return dlc of CAN frame

can_get_echo_skb() is usually called in the TX complete handler.
The stats->tx_packets and stats->tx_bytes should be updated there, too.
This patch simplifies to figure out the size of the sent CAN frame.
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/dev.c

@@ -327,16 +327,24 @@ EXPORT_SYMBOL_GPL(can_put_echo_skb);
  * is handled in the device driver. The driver must protect
  * access to priv->echo_skb, if necessary.
  */
-void can_get_echo_skb(struct net_device *dev, unsigned int idx)
+unsigned int can_get_echo_skb(struct net_device *dev, unsigned int idx)
 {
 	struct can_priv *priv = netdev_priv(dev);
 
 	BUG_ON(idx >= priv->echo_skb_max);
 
 	if (priv->echo_skb[idx]) {
+		struct sk_buff *skb = priv->echo_skb[idx];
+		struct can_frame *cf = (struct can_frame *)skb->data;
+		u8 dlc = cf->can_dlc;
+
 		netif_rx(priv->echo_skb[idx]);
 		priv->echo_skb[idx] = NULL;
+
+		return dlc;
 	}
+
+	return 0;
 }
 EXPORT_SYMBOL_GPL(can_get_echo_skb);
 

include/linux/can/dev.h

@@ -92,7 +92,7 @@ void can_bus_off(struct net_device *dev);
 
 void can_put_echo_skb(struct sk_buff *skb, struct net_device *dev,
 		      unsigned int idx);
-void can_get_echo_skb(struct net_device *dev, unsigned int idx);
+unsigned int can_get_echo_skb(struct net_device *dev, unsigned int idx);
 void can_free_echo_skb(struct net_device *dev, unsigned int idx);
 
 struct sk_buff *alloc_can_skb(struct net_device *dev, struct can_frame **cf);