A if `netdev_driver_t::confirm_send()` is provided, it provides the
new netdev API. However, detecting the API at runtime and handling
both API styles comes at a cost. This can be optimized in case only
new or only old style netdevs are in use.
To do so, this adds the pseudo modules `netdev_legacy_api` and
`netdev_new_api`. As right now no netdev actually implements the new
API, all netdevs pull in `netdev_legacy_api`. If `netdev_legacy_api` is
in used but `netdev_new_api` is not, we can safely assume at compile
time that only legacy netdevs are in use. Similar, if only
`netdev_new_api` is used, only support for the new API is needed. Only
when both are in use, run time checks are needed.
This provides two helper function to check for a netif if the
corresponding netdev implements the old or the new API. (With one
being the inverse of the other.) They are suitable for constant folding
when only new or only legacy devices are in use. Consequently, dead
branches should be eliminated by the optimizer.
The NETOPT_ADDRESS option of the nrf24l01p_ng driver modified the address of pipe 0 but the main listening
address was designed to be the address of pipe 1.
The driver uses the netdev interface. Due to the limited
capabilities of the transceiver (32 byte FIFO and no source address in the layer2 frame),
it relies on 6LowPAN compression and adds the source address to the frame for that.
