net: dsa: Add helper function to retrieve VLAN awareness setting

Since different types of hardware may or may not support this setting
per-port, DSA keeps it either in dsa_switch or in dsa_port.

While drivers may know the characteristics of their hardware and
retrieve it from the correct place without the need of helpers, it is
cumbersone to find out an unambigous answer from generic DSA code.

Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/dsa.h

@@ -305,6 +305,16 @@ static inline unsigned int dsa_upstream_port(struct dsa_switch *ds, int port)
 	return dsa_towards_port(ds, cpu_dp->ds->index, cpu_dp->index);
 }
 
+static inline bool dsa_port_is_vlan_filtering(const struct dsa_port *dp)
+{
+	const struct dsa_switch *ds = dp->ds;
+
+	if (ds->vlan_filtering_is_global)
+		return ds->vlan_filtering;
+	else
+		return dp->vlan_filtering;
+}
+
 typedef int dsa_fdb_dump_cb_t(const unsigned char *addr, u16 vid,
 			      bool is_static, void *data);
 struct dsa_switch_ops {