dev_open — prepare an interface for use.
| int fsfuncdev_open ( | struct net_device * dev ); | 
   Takes a device from down to up state. The device's private open
   function is invoked and then the multicast lists are loaded. Finally
   the device is moved into the up state and a NETDEV_UP message is
   sent to the netdev notifier chain.
   
Calling this function on an active interface is a nop. On a failure a negative errno code is returned.