[NET]: Dynamically allocate the loopback device, part 2.

Doing this makes loopback.c a better example of how to do a
simple network device, and it removes the special case
single static allocation of a struct net_device, hopefully
making maintenance easier.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Daniel Lezcano <dlezcano@fr.ibm.com>
Acked-By: Kirill Korotaev <dev@sw.ru>
Acked-by: Benjamin Thery <benjamin.thery@bull.net>

drivers/net/loopback.c

@@ -202,44 +202,60 @@ static const struct ethtool_ops loopback_ethtool_ops = {
  * The loopback device is special. There is only one instance and
  * it is statically allocated. Don't do this for other devices.
  */
-struct net_device __loopback_dev = {
-	.name	 		= "lo",
-	.get_stats		= &get_stats,
-	.mtu			= (16 * 1024) + 20 + 20 + 12,
-	.hard_start_xmit	= loopback_xmit,
-	.hard_header		= eth_header,
-	.hard_header_cache	= eth_header_cache,
-	.header_cache_update	= eth_header_cache_update,
-	.hard_header_len	= ETH_HLEN,	/* 14	*/
-	.addr_len		= ETH_ALEN,	/* 6	*/
-	.tx_queue_len		= 0,
-	.type			= ARPHRD_LOOPBACK,	/* 0x0001*/
-	.rebuild_header		= eth_rebuild_header,
-	.flags			= IFF_LOOPBACK,
-	.features 		= NETIF_F_SG | NETIF_F_FRAGLIST
+static void loopback_setup(struct net_device *dev)
+{
+	dev->get_stats		= &get_stats;
+	dev->mtu		= (16 * 1024) + 20 + 20 + 12;
+	dev->hard_start_xmit	= loopback_xmit;
+	dev->hard_header	= eth_header;
+	dev->hard_header_cache	= eth_header_cache;
+	dev->header_cache_update = eth_header_cache_update;
+	dev->hard_header_len	= ETH_HLEN;	/* 14	*/
+	dev->addr_len		= ETH_ALEN;	/* 6	*/
+	dev->tx_queue_len	= 0;
+	dev->type		= ARPHRD_LOOPBACK;	/* 0x0001*/
+	dev->rebuild_header	= eth_rebuild_header;
+	dev->flags		= IFF_LOOPBACK;
+	dev->features 		= NETIF_F_SG | NETIF_F_FRAGLIST
 #ifdef LOOPBACK_TSO
-				  | NETIF_F_TSO
+		| NETIF_F_TSO
 #endif
-				  | NETIF_F_NO_CSUM | NETIF_F_HIGHDMA
-				  | NETIF_F_LLTX
-				  | NETIF_F_NETNS_LOCAL,
-	.ethtool_ops		= &loopback_ethtool_ops,
-	.nd_net                 = &init_net,
-};
-
-struct net_device *loopback_dev = &__loopback_dev;
+		| NETIF_F_NO_CSUM
+		| NETIF_F_HIGHDMA
+		| NETIF_F_LLTX
+		| NETIF_F_NETNS_LOCAL,
+	dev->ethtool_ops	= &loopback_ethtool_ops;
+}
 
 /* Setup and register the loopback device. */
 static int __init loopback_init(void)
 {
-	int err = register_netdev(loopback_dev);
+	struct net_device *dev;
+	int err;
+
+	err = -ENOMEM;
+	dev = alloc_netdev(0, "lo", loopback_setup);
+	if (!dev)
+		goto out;
 
+	err = register_netdev(dev);
 	if (err)
-		panic("loopback: Failed to register netdevice: %d\n", err);
+		goto out_free_netdev;
 
+	err = 0;
+	loopback_dev = dev;
+
+out:
+	if (err)
+		panic("loopback: Failed to register netdevice: %d\n", err);
 	return err;
-};
 
-module_init(loopback_init);
+out_free_netdev:
+	free_netdev(dev);
+	goto out;
+}
+
+fs_initcall(loopback_init);
 
+struct net_device *loopback_dev;
 EXPORT_SYMBOL(loopback_dev);