net: dsa: add port_fdb_dump function

Not all switch chips support a Get Next operation to iterate on its FDB.
So add a more simple port_fdb_dump function for them.
Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/dsa.h

@@ -198,6 +198,7 @@ static inline u8 dsa_upstream_port(struct dsa_switch *ds)
 }
 
 struct switchdev_trans;
+struct switchdev_obj;
 struct switchdev_obj_port_fdb;
 
 struct dsa_switch_driver {
@@ -330,6 +331,9 @@ struct dsa_switch_driver {
 	int	(*port_fdb_getnext)(struct dsa_switch *ds, int port,
 				    unsigned char *addr, u16 *vid,
 				    bool *is_static);
+	int	(*port_fdb_dump)(struct dsa_switch *ds, int port,
+				 struct switchdev_obj_port_fdb *fdb,
+				 int (*cb)(struct switchdev_obj *obj));
 };
 
 void register_switch_driver(struct dsa_switch_driver *type);

net/dsa/slave.c

@@ -382,6 +382,9 @@ static int dsa_slave_port_fdb_dump(struct net_device *dev,
 	u16 vid = 0;
 	int ret;
 
+	if (ds->drv->port_fdb_dump)
+		return ds->drv->port_fdb_dump(ds, p->port, fdb, cb);
+
 	if (!ds->drv->port_fdb_getnext)
 		return -EOPNOTSUPP;