can: make the number of echo skb's configurable

This patch allows the CAN controller driver to define the number of echo
skb's used for the local loopback (echo), as suggested by Kurt Van
Dijck, with the function:

  struct net_device *alloc_candev(int sizeof_priv,
                                  unsigned int echo_skb_max);

The CAN drivers have been adapted accordingly. For the ems_usb driver,
as suggested by Sebastian Haas, the number of echo skb's has been
increased to 10, which improves the transmission performance a lot.

Signed-off-by: Wolfgang Grandegger <wg@grandegger.com>
Signed-off-by: Kurt Van Dijck <kurt.van.dijck@eia.be>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 26 insertions, 6 deletions

diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c
index f0b9a1e1db46..39b99f57c265 100644
--- a/drivers/net/can/dev.c
+++ b/drivers/net/can/dev.c
@@ -245,7 +245,7 @@ static void can_flush_echo_skb(struct net_device *dev)
 	struct net_device_stats *stats = &dev->stats;
 	int i;
 
-	for (i = 0; i < CAN_ECHO_SKB_MAX; i++) {
+	for (i = 0; i < priv->echo_skb_max; i++) {
 		if (priv->echo_skb[i]) {
 			kfree_skb(priv->echo_skb[i]);
 			priv->echo_skb[i] = NULL;
@@ -262,10 +262,13 @@ 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 idx)
+void can_put_echo_skb(struct sk_buff *skb, struct net_device *dev,
+		      unsigned int idx)
 {
 	struct can_priv *priv = netdev_priv(dev);
 
+	BUG_ON(idx >= priv->echo_skb_max);
+
 	/* check flag whether this packet has to be looped back */
 	if (!(dev->flags & IFF_ECHO) || skb->pkt_type != PACKET_LOOPBACK) {
 		kfree_skb(skb);
@@ -311,10 +314,12 @@ 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, int idx)
+void 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]) {
 		netif_rx(priv->echo_skb[idx]);
 		priv->echo_skb[idx] = NULL;
@@ -327,10 +332,12 @@ EXPORT_SYMBOL_GPL(can_get_echo_skb);
   *
   * The function is typically called when TX failed.
   */
-void can_free_echo_skb(struct net_device *dev, int idx)
+void can_free_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]) {
 		kfree_skb(priv->echo_skb[idx]);
 		priv->echo_skb[idx] = NULL;
@@ -445,17 +452,30 @@ static void can_setup(struct net_device *dev)
 /*
  * Allocate and setup space for the CAN network device
  */
-struct net_device *alloc_candev(int sizeof_priv)
+struct net_device *alloc_candev(int sizeof_priv, unsigned int echo_skb_max)
 {
 	struct net_device *dev;
 	struct can_priv *priv;
+	int size;
 
-	dev = alloc_netdev(sizeof_priv, "can%d", can_setup);
+	if (echo_skb_max)
+		size = ALIGN(sizeof_priv, sizeof(struct sk_buff *)) +
+			echo_skb_max * sizeof(struct sk_buff *);
+	else
+		size = sizeof_priv;
+
+	dev = alloc_netdev(size, "can%d", can_setup);
 	if (!dev)
 		return NULL;
 
 	priv = netdev_priv(dev);
 
+	if (echo_skb_max) {
+		priv->echo_skb_max = echo_skb_max;
+		priv->echo_skb = (void *)priv +
+			ALIGN(sizeof_priv, sizeof(struct sk_buff *));
+	}
+
 	priv->state = CAN_STATE_STOPPED;
 
 	init_timer(&priv->restart_timer);