Seeing bonding debug log data along the lines of "event: 5" is a bit spartan,
and often requires a lookup table if you don't remember what every event is.
Make use of netdev_cmd_to_name for an improved debugging experience, so for
the prior example, you'll see: "bond_netdev_event received NETDEV_REGISTER"
instead (both are prefixed with the device for which the event pertains).
There are also quite a few places that the netdev_dbg output could stand to
mention exactly which slave the message pertains to (gets messy if you have
multiple slaves all spewing at once to know which one they pertain to).