mv88e6xxx: Reject requests to enable time stamping on both edges.

This driver enables rising edge or falling edge, but not both, and so
this patch validates that the request contains only one of the two
edges.
Signed-off-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/mv88e6xxx/ptp.c

@@ -280,6 +280,12 @@ static int mv88e6352_ptp_enable_extts(struct mv88e6xxx_chip *chip,
 				PTP_STRICT_FLAGS))
 		return -EOPNOTSUPP;
 
+	/* Reject requests to enable time stamping on both edges. */
+	if ((rq->extts.flags & PTP_STRICT_FLAGS) &&
+	    (rq->extts.flags & PTP_ENABLE_FEATURE) &&
+	    (rq->extts.flags & PTP_EXTTS_EDGES) == PTP_EXTTS_EDGES)
+		return -EOPNOTSUPP;
+
 	pin = ptp_find_pin(chip->ptp_clock, PTP_PF_EXTTS, rq->extts.index);
 
 	if (pin < 0)