qlcnic: set mtu lower limit

Setting mtu < 68 is not supported.
Signed-off-by: Sritej Velaga <sritej.velaga@qlogic.com>
Signed-off-by: Amit Kumar Salecha <amit.salecha@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/qlcnic/qlcnic.h

@@ -95,6 +95,7 @@
 #define FIRST_PAGE_GROUP_END	0x100000
 
 #define P3_MAX_MTU                     (9600)
+#define P3_MIN_MTU                     (68)
 #define QLCNIC_MAX_ETHERHDR                32 /* This contains some padding */
 
 #define QLCNIC_P3_RX_BUF_MAX_LEN         (QLCNIC_MAX_ETHERHDR + ETH_DATA_LEN)

drivers/net/qlcnic/qlcnic_hw.c

@@ -758,9 +758,9 @@ int qlcnic_change_mtu(struct net_device *netdev, int mtu)
 	struct qlcnic_adapter *adapter = netdev_priv(netdev);
 	int rc = 0;
 
-	if (mtu > P3_MAX_MTU) {
-		dev_err(&adapter->netdev->dev, "mtu > %d bytes unsupported\n",
-						P3_MAX_MTU);
+	if (mtu < P3_MIN_MTU || mtu > P3_MAX_MTU) {
+		dev_err(&adapter->netdev->dev, "%d bytes < mtu < %d bytes"
+			" not supported\n", P3_MAX_MTU, P3_MIN_MTU);
 		return -EINVAL;
 	}