net: split eth_mac_addr for better error handling

When we set mac address, software mac address in system and hardware mac
address all need to be updated. Current eth_mac_addr() doesn't allow
callers to implement error handling nicely.

This patch split eth_mac_addr() to prepare part and real commit part,
then we can prepare first, and try to change hardware address, then do
the real commit if hardware address is set successfully.

Signed-off-by: Stefan Hajnoczi <stefanha@gmail.com>
Signed-off-by: Amos Kong <akong@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/etherdevice.h b/include/linux/etherdevice.h
index 1a43e1b..c623861 100644
--- a/include/linux/etherdevice.h
+++ b/include/linux/etherdevice.h
@@ -40,6 +40,8 @@
 extern void eth_header_cache_update(struct hh_cache *hh,
 				    const struct net_device *dev,
 				    const unsigned char *haddr);
+extern int eth_prepare_mac_addr_change(struct net_device *dev, void *p);
+extern void eth_commit_mac_addr_change(struct net_device *dev, void *p);
 extern int eth_mac_addr(struct net_device *dev, void *p);
 extern int eth_change_mtu(struct net_device *dev, int new_mtu);
 extern int eth_validate_addr(struct net_device *dev);