can: dev: can_put_echo_skb(): propagate error in case of errors

The function can_put_echo_skb() can fail for several reasons. It may
fail due to OOM, but when it fails it's usually due to locking problems
in the driver.

In order to help developing and debugging of new drivers propagate error
value in case of errors.

Link: https://lore.kernel.org/r/20200915223527.1417033-12-mkl@pengutronix.deSigned-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/dev.c

@@ -434,7 +434,7 @@ static void can_flush_echo_skb(struct net_device *dev)
  * of the device driver. The driver must protect access to
  * priv->echo_skb, if necessary.
  */
-void can_put_echo_skb(struct sk_buff *skb, struct net_device *dev,
+int can_put_echo_skb(struct sk_buff *skb, struct net_device *dev,
 		     unsigned int idx)
 {
 	struct can_priv *priv = netdev_priv(dev);
@@ -446,13 +446,13 @@ void can_put_echo_skb(struct sk_buff *skb, struct net_device *dev,
 	    (skb->protocol != htons(ETH_P_CAN) &&
 	     skb->protocol != htons(ETH_P_CANFD))) {
 		kfree_skb(skb);
-		return;
+		return 0;
 	}
 
 	if (!priv->echo_skb[idx]) {
 		skb = can_create_echo_skb(skb);
 		if (!skb)
-			return;
+			return -ENOMEM;
 
 		/* make settings for echo to reduce code in irq context */
 		skb->pkt_type = PACKET_BROADCAST;
@@ -465,7 +465,10 @@ void can_put_echo_skb(struct sk_buff *skb, struct net_device *dev,
 		/* locking problem with netif_stop_queue() ?? */
 		netdev_err(dev, "%s: BUG! echo_skb %d is occupied!\n", __func__, idx);
 		kfree_skb(skb);
+		return -EBUSY;
 	}
+
+	return 0;
 }
 EXPORT_SYMBOL_GPL(can_put_echo_skb);
 

include/linux/can/dev.h

@@ -201,7 +201,7 @@ void can_bus_off(struct net_device *dev);
 void can_change_state(struct net_device *dev, struct can_frame *cf,
 		      enum can_state tx_state, enum can_state rx_state);
 
-void can_put_echo_skb(struct sk_buff *skb, struct net_device *dev,
+int can_put_echo_skb(struct sk_buff *skb, struct net_device *dev,
 		     unsigned int idx);
 struct sk_buff *__can_get_echo_skb(struct net_device *dev, unsigned int idx,
 				   u8 *len_ptr);