net: dsa: Allow the DSA driver to indicate the tag protocol

DSA drivers may drive different families of switches which need
different tag protocol. Rather than hard code the tag protocol in the
driver structure, have a callback for the DSA core to call.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/dsa.h

@@ -239,14 +239,15 @@ struct switchdev_obj_port_vlan;
 struct dsa_switch_driver {
 	struct list_head	list;
 
-	enum dsa_tag_protocol	tag_protocol;
-
 	/*
 	 * Probing and setup.
 	 */
 	const char	*(*probe)(struct device *dsa_dev,
 				  struct device *host_dev, int sw_addr,
 				  void **priv);
+
+	enum dsa_tag_protocol (*get_tag_protocol)(struct dsa_switch *ds);
+
 	int	(*setup)(struct dsa_switch *ds);
 	int	(*set_addr)(struct dsa_switch *ds, u8 *addr);
 	u32	(*get_phy_flags)(struct dsa_switch *ds, int port);