[PATCH RFC net-next 04/19] net: dsa: tag_ar9331: split out common tag accessors

[Alexander Lobakin]

They will be reused in upcoming GRO callbacks.
(Almost) no functional changes except less informative error string.

Signed-off-by: Alexander Lobakin <alobakin@xxxxxxxx>
---
 net/dsa/tag_ar9331.c | 46 +++++++++++++++++++++++++++-----------------
 1 file changed, 28 insertions(+), 18 deletions(-)

diff --git a/net/dsa/tag_ar9331.c b/net/dsa/tag_ar9331.c
index 399ca21ec03b..c22c1b515e02 100644
--- a/net/dsa/tag_ar9331.c
+++ b/net/dsa/tag_ar9331.c
@@ -24,6 +24,25 @@
 #define AR9331_HDR_RESERVED_MASK	GENMASK(5, 4)
 #define AR9331_HDR_PORT_NUM_MASK	GENMASK(3, 0)
 
+static inline bool ar9331_tag_sanity_check(const u8 *data)
+{
+	u16 hdr = le16_to_cpup((__le16 *)(data - ETH_HLEN));
+
+	return FIELD_GET(AR9331_HDR_VERSION_MASK, hdr) == AR9331_HDR_VERSION &&
+	       !(hdr & AR9331_HDR_FROM_CPU);
+}
+
+static inline int ar9331_tag_source_port(const u8 *data)
+{
+	/* hdr comes in LE byte order, so srcport field is in the first byte */
+	return FIELD_GET(AR9331_HDR_PORT_NUM_MASK, *(data - ETH_HLEN));
+}
+
+static inline __be16 ar9331_tag_encap_proto(const u8 *data)
+{
+	return *(__be16 *)data;
+}
+
 static struct sk_buff *ar9331_tag_xmit(struct sk_buff *skb,
 				       struct net_device *dev)
 {
@@ -50,36 +69,27 @@ static struct sk_buff *ar9331_tag_rcv(struct sk_buff *skb,
 				      struct net_device *ndev,
 				      struct packet_type *pt)
 {
-	u8 ver, port;
-	u16 hdr;
+	int port;
 
 	if (unlikely(!pskb_may_pull(skb, AR9331_HDR_LEN)))
 		return NULL;
 
-	hdr = le16_to_cpu(*(__le16 *)skb_mac_header(skb));
-
-	ver = FIELD_GET(AR9331_HDR_VERSION_MASK, hdr);
-	if (unlikely(ver != AR9331_HDR_VERSION)) {
-		netdev_warn_once(ndev, "%s:%i wrong header version 0x%2x\n",
-				 __func__, __LINE__, hdr);
-		return NULL;
-	}
-
-	if (unlikely(hdr & AR9331_HDR_FROM_CPU)) {
-		netdev_warn_once(ndev, "%s:%i packet should not be from cpu 0x%2x\n",
-				 __func__, __LINE__, hdr);
+	if (unlikely(!ar9331_tag_sanity_check(skb->data))) {
+		netdev_warn_once(ndev,
+				 "%s:%i wrong header version or source port\n",
+				 __func__, __LINE__);
 		return NULL;
 	}
 
-	skb_pull_rcsum(skb, AR9331_HDR_LEN);
-
 	/* Get source port information */
-	port = FIELD_GET(AR9331_HDR_PORT_NUM_MASK, hdr);
+	port = ar9331_tag_source_port(skb->data);
 
 	skb->dev = dsa_master_find_slave(ndev, 0, port);
 	if (!skb->dev)
 		return NULL;
 
+	skb_pull_rcsum(skb, AR9331_HDR_LEN);
+
 	return skb;
 }
 
@@ -87,7 +97,7 @@ static void ar9331_tag_flow_dissect(const struct sk_buff *skb, __be16 *proto,
 				    int *offset)
 {
 	*offset = AR9331_HDR_LEN;
-	*proto = *(__be16 *)skb->data;
+	*proto = ar9331_tag_encap_proto(skb->data);
 }
 
 static const struct dsa_device_ops ar9331_netdev_ops = {
-- 
2.24.1