As we've introduced virtual inheritance to support EMACInterface, we can
no longer use C-style casts or static_cast to downcast from
NetworkInterface to more specific types. RTTI is disabled in the
toolchains, so dynamic_cast is unavailables.
Add virtual downcast methods to permit conversions to the 6 derived
classes. Probably only needed for EMACInterface, WiFiInterface and
EthInterface, but handles the set.
Rather than let "EthernetInterface" be the base EMAC NetworkInterface,
insert an "EMACInterface" class.
EthernetInterface then derives from EMACInterface and EthInterface.
A Wi-Fi driver can derive from EMACInterface and WiFiInterface - this
will be more logical than deriving from EthernetInterface and
WiFiInterface.
This does mean adding a couple of virtual inheritances to avoid
duplicate NetworkInterfaces:
NetworkInterface
/ \
virtual / \ virtual
/ \
EMACInterface WiFiInterface
\ /
\ /
\ /
MyCustomWiFiInterface
Kevin Bracey