net: add busy_poll device feature

Currently there is no way how to find out if a device supports busy
polling. So add a feature and make it dependent on ndo_busy_poll
existence.
Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netdev_features.h

@@ -63,6 +63,7 @@ enum {
 	NETIF_F_HW_VLAN_STAG_RX_BIT,	/* Receive VLAN STAG HW acceleration */
 	NETIF_F_HW_VLAN_STAG_FILTER_BIT,/* Receive filtering on VLAN STAGs */
 	NETIF_F_HW_L2FW_DOFFLOAD_BIT,	/* Allow L2 Forwarding in Hardware */
+	NETIF_F_BUSY_POLL_BIT,		/* Busy poll */
 
 	/*
 	 * Add your fresh new feature above and remember to update
@@ -118,6 +119,7 @@ enum {
 #define NETIF_F_HW_VLAN_STAG_RX	__NETIF_F(HW_VLAN_STAG_RX)
 #define NETIF_F_HW_VLAN_STAG_TX	__NETIF_F(HW_VLAN_STAG_TX)
 #define NETIF_F_HW_L2FW_DOFFLOAD	__NETIF_F(HW_L2FW_DOFFLOAD)
+#define NETIF_F_BUSY_POLL	__NETIF_F(BUSY_POLL)
 
 /* Features valid for ethtool to change */
 /* = all defined minus driver/device-class-related */

net/core/dev.c

@@ -5696,6 +5696,13 @@ static netdev_features_t netdev_fix_features(struct net_device *dev,
 		}
 	}
 
+#ifdef CONFIG_NET_RX_BUSY_POLL
+	if (dev->netdev_ops->ndo_busy_poll)
+		features |= NETIF_F_BUSY_POLL;
+	else
+#endif
+		features &= ~NETIF_F_BUSY_POLL;
+
 	return features;
 }
 

net/core/ethtool.c

@@ -97,6 +97,7 @@ static const char netdev_features_strings[NETDEV_FEATURE_COUNT][ETH_GSTRING_LEN]
 	[NETIF_F_RXFCS_BIT] =            "rx-fcs",
 	[NETIF_F_RXALL_BIT] =            "rx-all",
 	[NETIF_F_HW_L2FW_DOFFLOAD_BIT] = "l2-fwd-offload",
+	[NETIF_F_BUSY_POLL_BIT] =        "busy-poll",
 };
 
 static int ethtool_get_features(struct net_device *dev, void __user *useraddr)