[PATCH RFC net-next 14/19] net: dsa: tag_mtk: split out common tag accessors

@@ -10,12 +10,27 @@
 
 #include "dsa_priv.h"
 
-#define MTK_HDR_LEN		4
+#define MTK_HDR_LEN			4
 #define MTK_HDR_XMIT_UNTAGGED		0
 #define MTK_HDR_XMIT_TAGGED_TPID_8100	1
 #define MTK_HDR_RECV_SOURCE_PORT_MASK	GENMASK(2, 0)
 #define MTK_HDR_XMIT_DP_BIT_MASK	GENMASK(5, 0)
 
+static inline int mtk_tag_source_port(const u8 *data)
+{
+	/* The MTK header is added by the switch between src addr
+	 * and ethertype at this point, skb->data points to 2 bytes
+	 * after src addr so header should be 2 bytes right before.
+	 * The source port field is in the second byte of the tag.
+	 */
+	return *(data - 1) & MTK_HDR_RECV_SOURCE_PORT_MASK;
+}
+
+static inline __be16 mtk_tag_encap_proto(const u8 *data)
+{
+	return *(__be16 *)(data + 2);
+}
+
 static struct sk_buff *mtk_tag_xmit(struct sk_buff *skb,
 				    struct net_device *dev)
 {

@@ -60,17 +75,15 @@ static struct sk_buff *mtk_tag_rcv(struct sk_buff *skb, struct net_device *dev,
 				   struct packet_type *pt)
 {
 	int port;
-	__be16 *phdr, hdr;
 
 	if (unlikely(!pskb_may_pull(skb, MTK_HDR_LEN)))
 		return NULL;
 
-	/* The MTK header is added by the switch between src addr
-	 * and ethertype at this point, skb->data points to 2 bytes
-	 * after src addr so header should be 2 bytes right before.
-	 */
-	phdr = (__be16 *)(skb->data - 2);
-	hdr = ntohs(*phdr);
+	port = mtk_tag_source_port(skb->data);
+
+	skb->dev = dsa_master_find_slave(dev, 0, port);
+	if (!skb->dev)
+		return NULL;
 
 	/* Remove MTK tag and recalculate checksum. */
 	skb_pull_rcsum(skb, MTK_HDR_LEN);

@@ -79,21 +92,14 @@ static struct sk_buff *mtk_tag_rcv(struct sk_buff *skb, struct net_device *dev,
 		skb->data - ETH_HLEN - MTK_HDR_LEN,
 		2 * ETH_ALEN);
 
-	/* Get source port information */
-	port = (hdr & MTK_HDR_RECV_SOURCE_PORT_MASK);
-
-	skb->dev = dsa_master_find_slave(dev, 0, port);
-	if (!skb->dev)
-		return NULL;
-
 	return skb;
 }
 
 static void mtk_tag_flow_dissect(const struct sk_buff *skb, __be16 *proto,
 				 int *offset)
 {
-	*offset = 4;
-	*proto = ((__be16 *)skb->data)[1];
+	*offset = MTK_HDR_LEN;
+	*proto = mtk_tag_encap_proto(skb->data);
 }
 
 static const struct dsa_device_ops mtk_netdev_ops = {