net: dsa: b53: Deny enslaving port 7 for 7278 into a bridge

On 7278, port 7 connects to the ASP which should only receive frames
through the use of CFP rules, it is not desirable to have it be part of
a bridge at all since that would make it pick up unwanted traffic that
it may not even be able to filter or sustain.
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/b53/b53_common.c

@@ -1728,6 +1728,12 @@ int b53_br_join(struct dsa_switch *ds, int port, struct net_device *br)
 	u16 pvlan, reg;
 	unsigned int i;
 
+	/* On 7278, port 7 which connects to the ASP should only receive
+	 * traffic from matching CFP rules.
+	 */
+	if (dev->chip_id == BCM7278_DEVICE_ID && port == 7)
+		return -EINVAL;
+
 	/* Make this port leave the all VLANs join since we will have proper
 	 * VLAN entries from now on
 	 */