diff --git a/drivers/net/ethernet/broadcom/tg3.c b/drivers/net/ethernet/broadcom/tg3.c
index 77f3511..ca3aa12 100644
--- a/drivers/net/ethernet/broadcom/tg3.c
+++ b/drivers/net/ethernet/broadcom/tg3.c
@@ -6280,6 +6280,10 @@
 
 	switch (rq->type) {
 	case PTP_CLK_REQ_PEROUT:
+		/* Reject requests with unsupported flags */
+		if (rq->perout.flags)
+			return -EOPNOTSUPP;
+
 		if (rq->perout.index != 0)
 			return -EINVAL;
 
diff --git a/drivers/net/ethernet/intel/igb/igb_ptp.c b/drivers/net/ethernet/intel/igb/igb_ptp.c
index fd3071f..4997963 100644
--- a/drivers/net/ethernet/intel/igb/igb_ptp.c
+++ b/drivers/net/ethernet/intel/igb/igb_ptp.c
@@ -551,6 +551,10 @@
 		return 0;
 
 	case PTP_CLK_REQ_PEROUT:
+		/* Reject requests with unsupported flags */
+		if (rq->perout.flags)
+			return -EOPNOTSUPP;
+
 		if (on) {
 			pin = ptp_find_pin(igb->ptp_clock, PTP_PF_PEROUT,
 					   rq->perout.index);
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c b/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c
index 0059b29..cff6b60d 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c
@@ -290,6 +290,10 @@
 	if (!MLX5_PPS_CAP(mdev))
 		return -EOPNOTSUPP;
 
+	/* Reject requests with unsupported flags */
+	if (rq->perout.flags)
+		return -EOPNOTSUPP;
+
 	if (rq->perout.index >= clock->ptp_info.n_pins)
 		return -EINVAL;
 
diff --git a/drivers/net/ethernet/microchip/lan743x_ptp.c b/drivers/net/ethernet/microchip/lan743x_ptp.c
index 57b26c2..e8fe9a9 100644
--- a/drivers/net/ethernet/microchip/lan743x_ptp.c
+++ b/drivers/net/ethernet/microchip/lan743x_ptp.c
@@ -429,6 +429,10 @@
 	int pulse_width = 0;
 	int perout_bit = 0;
 
+	/* Reject requests with unsupported flags */
+	if (perout->flags)
+		return -EOPNOTSUPP;
+
 	if (!on) {
 		lan743x_ptp_perout_off(adapter);
 		return 0;
diff --git a/drivers/net/ethernet/renesas/ravb_ptp.c b/drivers/net/ethernet/renesas/ravb_ptp.c
index 9a42580..638f1fc 100644
--- a/drivers/net/ethernet/renesas/ravb_ptp.c
+++ b/drivers/net/ethernet/renesas/ravb_ptp.c
@@ -211,6 +211,10 @@
 	unsigned long flags;
 	int error = 0;
 
+	/* Reject requests with unsupported flags */
+	if (req->flags)
+		return -EOPNOTSUPP;
+
 	if (req->index)
 		return -EINVAL;
 
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c
index df638b1..0989e2b 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c
@@ -140,6 +140,10 @@
 
 	switch (rq->type) {
 	case PTP_CLK_REQ_PEROUT:
+		/* Reject requests with unsupported flags */
+		if (rq->perout.flags)
+			return -EOPNOTSUPP;
+
 		cfg = &priv->pps[rq->perout.index];
 
 		cfg->start.tv_sec = rq->perout.start.sec;
diff --git a/drivers/net/phy/dp83640.c b/drivers/net/phy/dp83640.c
index 6580094..04ad777 100644
--- a/drivers/net/phy/dp83640.c
+++ b/drivers/net/phy/dp83640.c
@@ -491,6 +491,9 @@
 		return 0;
 
 	case PTP_CLK_REQ_PEROUT:
+		/* Reject requests with unsupported flags */
+		if (rq->perout.flags)
+			return -EOPNOTSUPP;
 		if (rq->perout.index >= N_PER_OUT)
 			return -EINVAL;
 		return periodic_output(clock, rq, on, rq->perout.index);