net: dsa: mv88e6xxx: Create API to read a single stat counter

This change contains no functional change. We simply push the hardware
specific stats logic to a function reading a single counter, rather
than the whole set.

This is a preparatory change for the upcoming standard ethtool
statistics support (i.e. "eth-mac", "eth-ctrl" etc.).
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Signed-off-by: Tobias Waldekranz <tobias@waldekranz.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/mv88e6xxx/chip.h

@@ -318,6 +318,17 @@ struct mv88e6xxx_mst {
 	struct mv88e6xxx_stu_entry stu;
 };
 
+#define STATS_TYPE_PORT		BIT(0)
+#define STATS_TYPE_BANK0	BIT(1)
+#define STATS_TYPE_BANK1	BIT(2)
+
+struct mv88e6xxx_hw_stat {
+	char string[ETH_GSTRING_LEN];
+	size_t size;
+	int reg;
+	int type;
+};
+
 struct mv88e6xxx_chip {
 	const struct mv88e6xxx_info *info;
 
@@ -574,8 +585,9 @@ struct mv88e6xxx_ops {
 	/* Return the number of strings describing statistics */
 	int (*stats_get_sset_count)(struct mv88e6xxx_chip *chip);
 	int (*stats_get_strings)(struct mv88e6xxx_chip *chip,  uint8_t *data);
-	int (*stats_get_stats)(struct mv88e6xxx_chip *chip,  int port,
-			       uint64_t *data);
+	size_t (*stats_get_stat)(struct mv88e6xxx_chip *chip, int port,
+				 const struct mv88e6xxx_hw_stat *stat,
+				 uint64_t *data);
 	int (*set_cpu_port)(struct mv88e6xxx_chip *chip, int port);
 	int (*set_egress_port)(struct mv88e6xxx_chip *chip,
 			       enum mv88e6xxx_egress_direction direction,
@@ -727,17 +739,6 @@ struct mv88e6xxx_pcs_ops {
 
 };
 
-#define STATS_TYPE_PORT		BIT(0)
-#define STATS_TYPE_BANK0	BIT(1)
-#define STATS_TYPE_BANK1	BIT(2)
-
-struct mv88e6xxx_hw_stat {
-	char string[ETH_GSTRING_LEN];
-	size_t size;
-	int reg;
-	int type;
-};
-
 static inline bool mv88e6xxx_has_stu(struct mv88e6xxx_chip *chip)
 {
 	return chip->info->max_sid > 0 &&