net: dsa: mv88e6xxx: Fix mv88e6352_serdes_get_stats error path

mv88e6xxx_get_stats, which collects stats from various sources,
expects all callees to return the number of stats read. If an error
occurs, 0 should be returned.

Prevent future mishaps of this kind by updating the return type to
reflect this contract.

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

@@ -613,8 +613,8 @@ struct mv88e6xxx_ops {
 	int (*serdes_get_sset_count)(struct mv88e6xxx_chip *chip, int port);
 	int (*serdes_get_strings)(struct mv88e6xxx_chip *chip,  int port,
 				  uint8_t *data);
-	int (*serdes_get_stats)(struct mv88e6xxx_chip *chip,  int port,
-				uint64_t *data);
+	size_t (*serdes_get_stats)(struct mv88e6xxx_chip *chip, int port,
+				   uint64_t *data);
 
 	/* SERDES registers for ethtool */
 	int (*serdes_get_regs_len)(struct mv88e6xxx_chip *chip,  int port);

drivers/net/dsa/mv88e6xxx/serdes.c

@@ -177,8 +177,8 @@ static uint64_t mv88e6352_serdes_get_stat(struct mv88e6xxx_chip *chip,
 	return val;
 }
 
-int mv88e6352_serdes_get_stats(struct mv88e6xxx_chip *chip, int port,
-			       uint64_t *data)
+size_t mv88e6352_serdes_get_stats(struct mv88e6xxx_chip *chip, int port,
+				  uint64_t *data)
 {
 	struct mv88e6xxx_port *mv88e6xxx_port = &chip->ports[port];
 	struct mv88e6352_serdes_hw_stat *stat;
@@ -187,7 +187,7 @@ int mv88e6352_serdes_get_stats(struct mv88e6xxx_chip *chip, int port,
 
 	err = mv88e6352_g2_scratch_port_has_serdes(chip, port);
 	if (err <= 0)
-		return err;
+		return 0;
 
 	BUILD_BUG_ON(ARRAY_SIZE(mv88e6352_serdes_hw_stats) >
 		     ARRAY_SIZE(mv88e6xxx_port->serdes_stats));
@@ -429,8 +429,8 @@ static uint64_t mv88e6390_serdes_get_stat(struct mv88e6xxx_chip *chip, int lane,
 	return reg[0] | ((u64)reg[1] << 16) | ((u64)reg[2] << 32);
 }
 
-int mv88e6390_serdes_get_stats(struct mv88e6xxx_chip *chip, int port,
-			       uint64_t *data)
+size_t mv88e6390_serdes_get_stats(struct mv88e6xxx_chip *chip, int port,
+				  uint64_t *data)
 {
 	struct mv88e6390_serdes_hw_stat *stat;
 	int lane;

drivers/net/dsa/mv88e6xxx/serdes.h

@@ -127,13 +127,13 @@ unsigned int mv88e6390_serdes_irq_mapping(struct mv88e6xxx_chip *chip,
 int mv88e6352_serdes_get_sset_count(struct mv88e6xxx_chip *chip, int port);
 int mv88e6352_serdes_get_strings(struct mv88e6xxx_chip *chip,
 				 int port, uint8_t *data);
-int mv88e6352_serdes_get_stats(struct mv88e6xxx_chip *chip, int port,
-			       uint64_t *data);
+size_t mv88e6352_serdes_get_stats(struct mv88e6xxx_chip *chip, int port,
+				  uint64_t *data);
 int mv88e6390_serdes_get_sset_count(struct mv88e6xxx_chip *chip, int port);
 int mv88e6390_serdes_get_strings(struct mv88e6xxx_chip *chip,
 				 int port, uint8_t *data);
-int mv88e6390_serdes_get_stats(struct mv88e6xxx_chip *chip, int port,
-			       uint64_t *data);
+size_t mv88e6390_serdes_get_stats(struct mv88e6xxx_chip *chip, int port,
+				  uint64_t *data);
 
 int mv88e6352_serdes_get_regs_len(struct mv88e6xxx_chip *chip, int port);
 void mv88e6352_serdes_get_regs(struct mv88e6xxx_chip *chip, int port, void *_p);