net: dsa: Support prepended Broadcom tag

Add a new type: DSA_TAG_PROTO_PREPEND which allows us to support for the
4-bytes Broadcom tag that we already support, but in a format where it
is pre-pended to the packet instead of located between the MAC SA and
the Ethertyper (DSA_TAG_PROTO_BRCM).

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/dsa.h

@@ -29,6 +29,7 @@ struct fixed_phy_status;
 enum dsa_tag_protocol {
 	DSA_TAG_PROTO_NONE = 0,
 	DSA_TAG_PROTO_BRCM,
+	DSA_TAG_PROTO_BRCM_PREPEND,
 	DSA_TAG_PROTO_DSA,
 	DSA_TAG_PROTO_EDSA,
 	DSA_TAG_PROTO_KSZ,

net/dsa/Kconfig

@@ -19,6 +19,9 @@ if NET_DSA
 config NET_DSA_TAG_BRCM
 	bool
 
+config NET_DSA_TAG_BRCM_PREPEND
+	bool
+
 config NET_DSA_TAG_DSA
 	bool
 

net/dsa/Makefile

@@ -5,6 +5,7 @@ dsa_core-y += dsa.o dsa2.o legacy.o master.o port.o slave.o switch.o
 
 # tagging formats
 dsa_core-$(CONFIG_NET_DSA_TAG_BRCM) += tag_brcm.o
+dsa_core-$(CONFIG_NET_DSA_TAG_BRCM_PREPEND) += tag_brcm.o
 dsa_core-$(CONFIG_NET_DSA_TAG_DSA) += tag_dsa.o
 dsa_core-$(CONFIG_NET_DSA_TAG_EDSA) += tag_edsa.o
 dsa_core-$(CONFIG_NET_DSA_TAG_KSZ) += tag_ksz.o

net/dsa/dsa.c

@@ -44,6 +44,9 @@ const struct dsa_device_ops *dsa_device_ops[DSA_TAG_LAST] = {
 #ifdef CONFIG_NET_DSA_TAG_BRCM
 	[DSA_TAG_PROTO_BRCM] = &brcm_netdev_ops,
 #endif
+#ifdef CONFIG_NET_DSA_TAG_BRCM_PREPEND
+	[DSA_TAG_PROTO_BRCM_PREPEND] = &brcm_prepend_netdev_ops,
+#endif
 #ifdef CONFIG_NET_DSA_TAG_DSA
 	[DSA_TAG_PROTO_DSA] = &dsa_netdev_ops,
 #endif

net/dsa/dsa_priv.h

@@ -191,6 +191,7 @@ void dsa_switch_unregister_notifier(struct dsa_switch *ds);
 
 /* tag_brcm.c */
 extern const struct dsa_device_ops brcm_netdev_ops;
+extern const struct dsa_device_ops brcm_prepend_netdev_ops;
 
 /* tag_dsa.c */
 extern const struct dsa_device_ops dsa_netdev_ops;

net/dsa/tag_brcm.c

@@ -96,13 +96,6 @@ static struct sk_buff *brcm_tag_xmit_ll(struct sk_buff *skb,
 	return skb;
 }
 
-static struct sk_buff *brcm_tag_xmit(struct sk_buff *skb,
-				     struct net_device *dev)
-{
-	/* Build the tag after the MAC Source Address */
-	return brcm_tag_xmit_ll(skb, dev, 2 * ETH_ALEN);
-}
-
 static struct sk_buff *brcm_tag_rcv_ll(struct sk_buff *skb,
 				       struct net_device *dev,
 				       struct packet_type *pt,
@@ -139,6 +132,15 @@ static struct sk_buff *brcm_tag_rcv_ll(struct sk_buff *skb,
 	return skb;
 }
 
+#ifdef CONFIG_NET_DSA_TAG_BRCM
+static struct sk_buff *brcm_tag_xmit(struct sk_buff *skb,
+				     struct net_device *dev)
+{
+	/* Build the tag after the MAC Source Address */
+	return brcm_tag_xmit_ll(skb, dev, 2 * ETH_ALEN);
+}
+
+
 static struct sk_buff *brcm_tag_rcv(struct sk_buff *skb, struct net_device *dev,
 				    struct packet_type *pt)
 {
@@ -161,3 +163,26 @@ const struct dsa_device_ops brcm_netdev_ops = {
 	.xmit	= brcm_tag_xmit,
 	.rcv	= brcm_tag_rcv,
 };
+#endif
+
+#ifdef CONFIG_NET_DSA_TAG_BRCM_PREPEND
+static struct sk_buff *brcm_tag_xmit_prepend(struct sk_buff *skb,
+					     struct net_device *dev)
+{
+	/* tag is prepended to the packet */
+	return brcm_tag_xmit_ll(skb, dev, 0);
+}
+
+static struct sk_buff *brcm_tag_rcv_prepend(struct sk_buff *skb,
+					    struct net_device *dev,
+					    struct packet_type *pt)
+{
+	/* tag is prepended to the packet */
+	return brcm_tag_rcv_ll(skb, dev, pt, ETH_HLEN);
+}
+
+const struct dsa_device_ops brcm_prepend_netdev_ops = {
+	.xmit	= brcm_tag_xmit_prepend,
+	.rcv	= brcm_tag_rcv_prepend,
+};
+#endif