net: dsa: add dsa_is_unused_port helper

As the comment above the chunk states, the b53 driver attempts to
disable the unused ports. But using ds->enabled_port_mask is misleading,
because this mask reports in fact the user ports.

To avoid confusion and fix this, this patch introduces an explicit
dsa_is_unused_port helper which ensures the corresponding bit is not
masked in any of the switch port masks.
Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/b53/b53_common.c

@@ -873,7 +873,7 @@ static int b53_setup(struct dsa_switch *ds)
 	for (port = 0; port < dev->num_ports; port++) {
 		if (dsa_is_cpu_port(ds, port))
 			b53_enable_cpu_port(dev, port);
-		else if (!(BIT(port) & ds->enabled_port_mask))
+		else if (dsa_is_unused_port(ds, port))
 			b53_disable_port(ds, port, NULL);
 	}
 

include/net/dsa.h

@@ -254,6 +254,13 @@ struct dsa_switch {
 	struct dsa_port ports[];
 };
 
+static inline bool dsa_is_unused_port(struct dsa_switch *ds, int p)
+{
+	u32 m = ds->enabled_port_mask | ds->dsa_port_mask | ds->cpu_port_mask;
+
+	return !(m & BIT(p));
+}
+
 static inline bool dsa_is_cpu_port(struct dsa_switch *ds, int p)
 {
 	return !!(ds->cpu_port_mask & (1 << p));