net: introduce NETDEV_POST_INIT notifier

For various purposes including a wireless extensions
bugfix, we need to hook into the netdev creation before
before netdev_register_kobject(). This will also ease
doing the dev type assignment that Marcel was working
on for cfg80211 drivers w/o touching them all.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/notifier.h

@@ -201,6 +201,7 @@ static inline int notifier_to_errno(int ret)
 #define NETDEV_PRE_UP		0x000D
 #define NETDEV_BONDING_OLDTYPE  0x000E
 #define NETDEV_BONDING_NEWTYPE  0x000F
+#define NETDEV_POST_INIT	0x0010
 
 #define SYS_DOWN	0x0001	/* Notify of system down */
 #define SYS_RESTART	SYS_DOWN

net/core/dev.c

@@ -4836,6 +4836,12 @@ int register_netdevice(struct net_device *dev)
 		dev->features |= NETIF_F_GSO;
 
 	netdev_initialize_kobject(dev);
+
+	ret = call_netdevice_notifiers(NETDEV_POST_INIT, dev);
+	ret = notifier_to_errno(ret);
+	if (ret)
+		goto err_uninit;
+
 	ret = netdev_register_kobject(dev);
 	if (ret)
 		goto err_uninit;