[PATCH RFC net-next 07/19] net: dsa: tag_gswip: switch to bitfield helpers

[Alexander Lobakin <alobakin@dlink.ru>]

Make code look cleaner and more readable by using bitfield macros instead
of open-coding masks and shifts.
Misc: remove redundant variable in gswip_tag_xmit(), make dsa_port const.

Signed-off-by: Alexander Lobakin <alobakin@dlink.ru>
---
 net/dsa/tag_gswip.c | 24 +++++++++---------------
 1 file changed, 9 insertions(+), 15 deletions(-)

diff --git a/net/dsa/tag_gswip.c b/net/dsa/tag_gswip.c
index 408d4af390a0..de920f6aac5b 100644
--- a/net/dsa/tag_gswip.c
+++ b/net/dsa/tag_gswip.c
@@ -5,6 +5,7 @@
  * Copyright (C) 2017 - 2018 Hauke Mehrtens <hauke@hauke-m.de>
  */
 
+#include <linux/bitfield.h>
 #include <linux/bitops.h>
 #include <linux/etherdevice.h>
 #include <linux/skbuff.h>
@@ -45,26 +46,22 @@
 #define GSWIP_TX_CLASS_MASK		GENMASK(3, 0)
 
 /* Byte 3 */
+#define GSWIP_TX_PORT_MAP(port)		FIELD_PREP(GENMASK(6, 1), BIT(port))
 #define GSWIP_TX_DPID_EN		BIT(0)
-#define GSWIP_TX_PORT_MAP_SHIFT		1
-#define GSWIP_TX_PORT_MAP_MASK		GENMASK(6, 1)
 
-#define GSWIP_RX_HEADER_LEN	8
+#define GSWIP_RX_HEADER_LEN		8
 
 /* special tag in RX path header */
 /* Byte 7 */
-#define GSWIP_RX_SPPID_SHIFT		4
-#define GSWIP_RX_SPPID_MASK		GENMASK(6, 4)
+#define GSWIP_RX_SPPID(byte_7)		FIELD_GET(GENMASK(6, 4), byte_7)
 
 static struct sk_buff *gswip_tag_xmit(struct sk_buff *skb,
 				      struct net_device *dev)
 {
-	struct dsa_port *dp = dsa_slave_to_port(dev);
-	int err;
+	const struct dsa_port *dp = dsa_slave_to_port(dev);
 	u8 *gswip_tag;
 
-	err = skb_cow_head(skb, GSWIP_TX_HEADER_LEN);
-	if (err)
+	if (skb_cow_head(skb, GSWIP_TX_HEADER_LEN))
 		return NULL;
 
 	skb_push(skb, GSWIP_TX_HEADER_LEN);
@@ -73,8 +70,7 @@ static struct sk_buff *gswip_tag_xmit(struct sk_buff *skb,
 	gswip_tag[0] = GSWIP_TX_SLPID_CPU;
 	gswip_tag[1] = GSWIP_TX_DPID_ELAN;
 	gswip_tag[2] = GSWIP_TX_PORT_MAP_EN | GSWIP_TX_PORT_MAP_SEL;
-	gswip_tag[3] = BIT(dp->index + GSWIP_TX_PORT_MAP_SHIFT) & GSWIP_TX_PORT_MAP_MASK;
-	gswip_tag[3] |= GSWIP_TX_DPID_EN;
+	gswip_tag[3] = GSWIP_TX_PORT_MAP(dp->index) | GSWIP_TX_DPID_EN;
 
 	return skb;
 }
@@ -84,15 +80,13 @@ static struct sk_buff *gswip_tag_rcv(struct sk_buff *skb,
 				     struct packet_type *pt)
 {
 	int port;
-	u8 *gswip_tag;
 
 	if (unlikely(!pskb_may_pull(skb, GSWIP_RX_HEADER_LEN)))
 		return NULL;
 
-	gswip_tag = skb->data - ETH_HLEN;
-
 	/* Get source port information */
-	port = (gswip_tag[7] & GSWIP_RX_SPPID_MASK) >> GSWIP_RX_SPPID_SHIFT;
+	port = GSWIP_RX_SPPID(*(skb->data - ETH_HLEN + 7));
+
 	skb->dev = dsa_master_find_slave(dev, 0, port);
 	if (!skb->dev)
 		return NULL;
-- 
2.24.1