[netdevice] Make all net_driver methods optional

Most network upper-layer drivers do not implement all three methods
(probe, notify, and remove).  Save code by making all methods
optional.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/arch/i386/core/cachedhcp.c

 	return 0;
 }
 
-/**
- * Handle network device link state change
- *
- * @v netdev		Network device
- */
-static void cachedhcp_notify ( struct net_device *netdev __unused ) {
-
-	/* Nothing to do */
-}
-
-/**
- * Handle network device removal
- *
- * @v netdev		Network device
- */
-static void cachedhcp_remove ( struct net_device *netdev __unused ) {
-
-	/* Nothing to do */
-}
-
 /** Cached DHCP packet network device driver */
 struct net_driver cachedhcp_driver __net_driver = {
 	.name = "cachedhcp",
 	.probe = cachedhcp_probe,
-	.notify = cachedhcp_notify,
-	.remove = cachedhcp_remove,
 };

src/arch/i386/interface/vmware/guestinfo.c

 	return rc;
 }
 
-/**
- * Handle network device or link state change
- *
- * @v netdev		Network device
- */
-static void guestinfo_net_notify ( struct net_device *netdev __unused ) {
-	/* Nothing to do */
-}
-
 /**
  * Remove per-netdevice GuestInfo settings
  *
 struct net_driver guestinfo_net_driver __net_driver = {
 	.name = "GuestInfo",
 	.probe = guestinfo_net_probe,
-	.notify = guestinfo_net_notify,
 	.remove = guestinfo_net_remove,
 };

src/net/ipv6.c

 	return 0;
 }
 
-/**
- * Handle IPv6 network device or link state change
- *
- * @v netdev		Network device
- */
-static void ipv6_notify ( struct net_device *netdev __unused ) {
-
-	/* Nothing to do */
-}
-
 /**
  * Destroy IPv6 network device
  *
 struct net_driver ipv6_driver __net_driver = {
 	.name = "IPv6",
 	.probe = ipv6_probe,
-	.notify = ipv6_notify,
 	.remove = ipv6_remove,
 };
 

src/net/neighbour.c

 	return 0;
 }
 
-/**
- * Update neighbour cache on network device creation
- *
- * @v netdev		Network device
- */
-static int neighbour_probe ( struct net_device *netdev __unused ) {
-	/* Nothing to do */
-	return 0;
-}
-
 /**
  * Update neighbour cache on network device state change or removal
  *
 /** Neighbour driver (for net device notifications) */
 struct net_driver neighbour_net_driver __net_driver = {
 	.name = "Neighbour",
-	.probe = neighbour_probe,
 	.notify = neighbour_flush,
 	.remove = neighbour_flush,
 };

src/net/netdevice.c

 static void netdev_notify ( struct net_device *netdev ) {
 	struct net_driver *driver;
 
-	for_each_table_entry ( driver, NET_DRIVERS )
-		driver->notify ( netdev );
+	for_each_table_entry ( driver, NET_DRIVERS ) {
+		if ( driver->notify )
+			driver->notify ( netdev );
+	}
 }
 
 /**
 
 	/* Probe device */
 	for_each_table_entry ( driver, NET_DRIVERS ) {
-		if ( ( rc = driver->probe ( netdev ) ) != 0 ) {
+		if ( driver->probe && ( rc = driver->probe ( netdev ) ) != 0 ) {
 			DBGC ( netdev, "NETDEV %s could not add %s device: "
 			       "%s\n", netdev->name, driver->name,
 			       strerror ( rc ) );
 	return 0;
 
  err_probe:
-	for_each_table_entry_continue_reverse ( driver, NET_DRIVERS )
-		driver->remove ( netdev );
+	for_each_table_entry_continue_reverse ( driver, NET_DRIVERS ) {
+		if ( driver->remove )
+			driver->remove ( netdev );
+	}
 	clear_settings ( netdev_settings ( netdev ) );
 	unregister_settings ( netdev_settings ( netdev ) );
  err_register_settings:
 	netdev_close ( netdev );
 
 	/* Remove device */
-	for_each_table_entry_reverse ( driver, NET_DRIVERS )
-		driver->remove ( netdev );
+	for_each_table_entry_reverse ( driver, NET_DRIVERS ) {
+		if ( driver->remove )
+			driver->remove ( netdev );
+	}
 
 	/* Unregister per-netdev configuration settings */
 	clear_settings ( netdev_settings ( netdev ) );

src/net/vlan.c

 	return 0;
 }
 
-/**
- * Do nothing
- *
- * @v trunk		Trunk network device
- * @ret rc		Return status code
- */
-static int vlan_probe ( struct net_device *trunk __unused ) {
-	return 0;
-}
-
 /**
  * Handle trunk network device link state change
  *
 /** VLAN driver */
 struct net_driver vlan_driver __net_driver = {
 	.name = "VLAN",
-	.probe = vlan_probe,
 	.notify = vlan_notify,
 	.remove = vlan_remove,
 };