WAN: HDLC: Call notifiers before and after changing device type

An HDLC device can change type when the protocol driver is changed.
Calling the notifier change allows potential users of the interface
know about this planned change, and even block it. After the change
has occurred, send a second notification to users can evaluate the new
device type etc.

Signed-off-by: Andrew Lunn <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/wan/hdlc.c

···
 int attach_hdlc_protocol(struct net_device *dev, struct hdlc_proto *proto,
 			 size_t size)
 {
-	detach_hdlc_protocol(dev);
+	int err;
+
+	err = detach_hdlc_protocol(dev);
+	if (err)
+		return err;
 
 	if (!try_module_get(proto->module))
 		return -ENOSYS;
···
 		}
 	}
 	dev_to_hdlc(dev)->proto = proto;
+
 	return 0;
 }
 
 
-void detach_hdlc_protocol(struct net_device *dev)
+int detach_hdlc_protocol(struct net_device *dev)
 {
 	hdlc_device *hdlc = dev_to_hdlc(dev);
+	int err;
 
 	if (hdlc->proto) {
+		err = call_netdevice_notifiers(NETDEV_PRE_TYPE_CHANGE, dev);
+		err = notifier_to_errno(err);
+		if (err) {
+			netdev_err(dev, "Refused to change device type\n");
+			return err;
+		}
+
 		if (hdlc->proto->detach)
 			hdlc->proto->detach(dev);
 		module_put(hdlc->proto->module);
···
 	kfree(hdlc->state);
 	hdlc->state = NULL;
 	hdlc_setup_dev(dev);
+
+	return 0;
 }
 
 

drivers/net/wan/hdlc_cisco.c

···
 		spin_lock_init(&state(hdlc)->lock);
 		dev->header_ops = &cisco_header_ops;
 		dev->type = ARPHRD_CISCO;
+		call_netdevice_notifiers(NETDEV_POST_TYPE_CHANGE, dev);
 		netif_dormant_on(dev);
 		return 0;
 	}

drivers/net/wan/hdlc_fr.c

···
 		}
 		memcpy(&state(hdlc)->settings, &new_settings, size);
 		dev->type = ARPHRD_FRAD;
+		call_netdevice_notifiers(NETDEV_POST_TYPE_CHANGE, dev);
 		return 0;
 
 	case IF_PROTO_FR_ADD_PVC:

drivers/net/wan/hdlc_ppp.c

···
 		dev->hard_header_len = sizeof(struct hdlc_header);
 		dev->header_ops = &ppp_header_ops;
 		dev->type = ARPHRD_PPP;
+		call_netdevice_notifiers(NETDEV_POST_TYPE_CHANGE, dev);
 		netif_dormant_on(dev);
 		return 0;
 	}

drivers/net/wan/hdlc_raw.c

···
 			return result;
 		memcpy(hdlc->state, &new_settings, size);
 		dev->type = ARPHRD_RAWHDLC;
+		call_netdevice_notifiers(NETDEV_POST_TYPE_CHANGE, dev);
 		netif_dormant_off(dev);
 		return 0;
 	}

drivers/net/wan/hdlc_raw_eth.c

···
 		ether_setup(dev);
 		dev->tx_queue_len = old_qlen;
 		eth_hw_addr_random(dev);
+		call_netdevice_notifiers(NETDEV_POST_TYPE_CHANGE, dev);
 		netif_dormant_off(dev);
 		return 0;
 	}

drivers/net/wan/hdlc_x25.c

···
 		if ((result = attach_hdlc_protocol(dev, &proto, 0)))
 			return result;
 		dev->type = ARPHRD_X25;
+		call_netdevice_notifiers(NETDEV_POST_TYPE_CHANGE, dev);
 		netif_dormant_off(dev);
 		return 0;
 	}

include/linux/hdlc.h

···
 int attach_hdlc_protocol(struct net_device *dev, struct hdlc_proto *proto,
 			 size_t size);
 /* May be used by hardware driver to gain control over HDLC device */
-void detach_hdlc_protocol(struct net_device *dev);
+int detach_hdlc_protocol(struct net_device *dev);
 
 static __inline__ __be16 hdlc_type_trans(struct sk_buff *skb,
 					 struct net_device *dev)