Re: 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 <redacted>
Signed-off-by: Kurt Van Dijck <kurt.van.dijck-/BeEPy95v10@public.gmane.org>
---
 drivers/net/can/at91_can.c        |    2 +-
 drivers/net/can/dev.c             |   32 ++++++++++++++++++++++++++------
 drivers/net/can/sja1000/sja1000.c |    3 ++-
 drivers/net/can/sja1000/sja1000.h |    2 ++
 drivers/net/can/ti_hecc.c         |    6 +-----
 drivers/net/can/usb/ems_usb.c     |    4 ++--
 include/linux/can/dev.h           |   16 ++++++++--------
 7 files changed, 42 insertions(+), 23 deletions(-)

Index: net-next-2.6/drivers/net/can/dev.c
===================================================================

--- net-next-2.6.orig/drivers/net/can/dev.c
+++ net-next-2.6/drivers/net/can/dev.c

@@ -245,7 +245,7 @@ static void can_flush_echo_skb(struct ne
 	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 ne
  * 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 
 /*
  * 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);

Index: net-next-2.6/include/linux/can/dev.h
===================================================================

--- net-next-2.6.orig/include/linux/can/dev.h
+++ net-next-2.6/include/linux/can/dev.h

@@ -29,8 +29,6 @@ enum can_mode {
 /*
  * CAN common private data
  */
-#define CAN_ECHO_SKB_MAX  4
-
 struct can_priv {
 	struct can_device_stats can_stats;
 

@@ -44,15 +42,16 @@ struct can_priv {
 	int restart_ms;
 	struct timer_list restart_timer;
 
-	struct sk_buff *echo_skb[CAN_ECHO_SKB_MAX];
-
 	int (*do_set_bittiming)(struct net_device *dev);
 	int (*do_set_mode)(struct net_device *dev, enum can_mode mode);
 	int (*do_get_state)(const struct net_device *dev,
 			    enum can_state *state);
+
+	unsigned int echo_skb_max;
+	struct sk_buff **echo_skb;
 };
 
-struct net_device *alloc_candev(int sizeof_priv);
+struct net_device *alloc_candev(int sizeof_priv, unsigned int echo_skb_max);
 void free_candev(struct net_device *dev);
 
 int open_candev(struct net_device *dev);

@@ -64,8 +63,9 @@ void unregister_candev(struct net_device
 int can_restart_now(struct net_device *dev);
 void can_bus_off(struct net_device *dev);
 
-void can_put_echo_skb(struct sk_buff *skb, struct net_device *dev, int idx);
-void can_get_echo_skb(struct net_device *dev, int idx);
-void can_free_echo_skb(struct net_device *dev, int idx);
+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);
+void can_free_echo_skb(struct net_device *dev, unsigned int idx);
 
 #endif /* CAN_DEV_H */

Index: net-next-2.6/drivers/net/can/at91_can.c
===================================================================

--- net-next-2.6.orig/drivers/net/can/at91_can.c
+++ net-next-2.6/drivers/net/can/at91_can.c

@@ -1087,7 +1087,7 @@ static int __init at91_can_probe(struct 
 		goto exit_release;
 	}
 
-	dev = alloc_candev(sizeof(struct at91_priv));
+	dev = alloc_candev(sizeof(struct at91_priv), AT91_MB_TX_NUM);
 	if (!dev) {
 		err = -ENOMEM;
 		goto exit_iounmap;