net: dsa: reduce number of protocol hooks

DSA is currently registering one packet_type function per EtherType it
needs to intercept in the receive path of a DSA-enabled Ethernet device.
Right now we have three of them: trailer, DSA and eDSA, and there might
be more in the future, this will not scale to the addition of new
protocols.

This patch proceeds with adding a new layer of abstraction and two new
functions:

dsa_switch_rcv() which will dispatch into the tag-protocol specific
receive function implemented by net/dsa/tag_*.c

dsa_slave_xmit() which will dispatch into the tag-protocol specific
transmit function implemented by net/dsa/tag_*.c

When we do create the per-port slave network devices, we iterate over
the switch protocol to assign the DSA-specific receive and transmit
operations.

A new fake ethertype value is used: ETH_P_XDSA to illustrate the fact
that this is no longer going to look like ETH_P_DSA or ETH_P_TRAILER
like it used to be.

This allows us to greatly simplify the check in eth_type_trans() and
always override the skb->protocol with ETH_P_XDSA for Ethernet switches
tagged protocol, while also reducing the number repetitive slave
netdevice_ops assignments.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 12 insertions, 16 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 039b23786c22..1875dc71422a 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1781,24 +1781,13 @@ void dev_net_set(struct net_device *dev, struct net *net)
 #endif
 }
 
-static inline bool netdev_uses_dsa_tags(struct net_device *dev)
+static inline bool netdev_uses_dsa(struct net_device *dev)
 {
-#ifdef CONFIG_NET_DSA_TAG_DSA
-	if (dev->dsa_ptr != NULL)
-		return dsa_uses_dsa_tags(dev->dsa_ptr);
-#endif
-
-	return 0;
-}
-
-static inline bool netdev_uses_trailer_tags(struct net_device *dev)
-{
-#ifdef CONFIG_NET_DSA_TAG_TRAILER
-	if (dev->dsa_ptr != NULL)
-		return dsa_uses_trailer_tags(dev->dsa_ptr);
+#ifdef CONFIG_NET_DSA
+	return dev->dsa_ptr != NULL;
+#else
+	return false;
 #endif
-
-	return 0;
 }
 
 /**
@@ -1933,6 +1922,13 @@ struct udp_offload {
 	struct offload_callbacks callbacks;
 };
 
+struct dsa_device_ops {
+	netdev_tx_t (*xmit)(struct sk_buff *skb, struct net_device *dev);
+	int (*rcv)(struct sk_buff *skb, struct net_device *dev,
+		   struct packet_type *pt, struct net_device *orig_dev);
+};
+
+
 /* often modified stats are per cpu, other are shared (netdev->stats) */
 struct pcpu_sw_netstats {
 	u64     rx_packets;