net: mscc: improve the frame header parsing readability

This cosmetic patch improves the frame header parsing readability by
introducing a new macro to access and mask its fields.

Signed-off-by: Antoine Tenart <antoine.tenart@bootlin.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mscc/ocelot_board.c

@@ -16,24 +16,26 @@
 
 #include "ocelot.h"
 
-static int ocelot_parse_ifh(u32 *ifh, struct frame_info *info)
+#define IFH_EXTRACT_BITFIELD64(x, o, w) (((x) >> (o)) & GENMASK_ULL((w) - 1, 0))
+
+static int ocelot_parse_ifh(u32 *_ifh, struct frame_info *info)
 {
-	int i;
 	u8 llen, wlen;
+	u64 ifh[2];
+
+	ifh[0] = be64_to_cpu(((__force __be64 *)_ifh)[0]);
+	ifh[1] = be64_to_cpu(((__force __be64 *)_ifh)[1]);
 
-	/* The IFH is in network order, switch to CPU order */
-	for (i = 0; i < IFH_LEN; i++)
-		ifh[i] = ntohl((__force __be32)ifh[i]);
+	wlen = IFH_EXTRACT_BITFIELD64(ifh[0], 7,  8);
+	llen = IFH_EXTRACT_BITFIELD64(ifh[0], 15,  6);
 
-	wlen = (ifh[1] >> 7) & 0xff;
-	llen = (ifh[1] >> 15) & 0x3f;
 	info->len = OCELOT_BUFFER_CELL_SZ * wlen + llen - 80;
 
-	info->port = (ifh[2] & GENMASK(14, 11)) >> 11;
+	info->port = IFH_EXTRACT_BITFIELD64(ifh[1], 43, 4);
 
-	info->cpuq = (ifh[3] & GENMASK(27, 20)) >> 20;
-	info->tag_type = (ifh[3] & BIT(16)) >> 16;
-	info->vid = ifh[3] & GENMASK(11, 0);
+	info->cpuq = IFH_EXTRACT_BITFIELD64(ifh[1], 20, 8);
+	info->tag_type = IFH_EXTRACT_BITFIELD64(ifh[1], 16,  1);
+	info->vid = IFH_EXTRACT_BITFIELD64(ifh[1], 0,  12);
 
 	return 0;
 }