drivers/dose: implement netdev API async

[maribu]

Contribution description

This changes the behavior of the netdev implementation to match what async drivers do. The current implementation is synchronous, but that can be fixed once an async UART API is available.

In any case, we rather should not complicate testing of the network stack by having network devices come in different flavors.

Testing procedure

No regressions in DOSE

Issues/PRs references

None

[maribu]

@elenaf9 FYI

[benpicco]

Will this really simplify things? We still need the

    if (gnrc_netif_netdev_legacy_api(netif) || (res != 0)) {
        _tx_done(netif, pkt, tx_sync, res, push_back);
    }

check regardless - even if we get rid of gnrc_netif_netdev_legacy_api() we would still have

    int res = netif->ops->send(netif, pkt);
    if (res != 0) {
        _tx_done(netif, pkt, tx_sync, res, push_back);
    }

so we get the behavior that blocking netdevs can return the number of sent bytes directly for free.

[maribu]

I really would like to get rid of any driver details leaking into the network stack. Right now we have to test every network stack change with at least three drivers (legacy, new async, new sync) to be sure we don't introduce any regressions. I really would like to get back where a CI test on native would catch any network stack breakage.

But maybe the better approach here would be to just add an async UART API and turn DOSE/SLIP/ETHOS to a truly async driver, not one that fakes being async.

A transmission of a large frame via UART can take ages. E.g. sending 256 B with 10 bits per byte (1 start bit, 8 data bits, 0 parity bits, 1 stop bit) would mean blocking the thread for 22 ms at 115,200 Baud or 267 ms at 9,600 Baud. If we do not want to be force to spawn one thread for each and every netdev, those latency are pretty prohibitive.

[benpicco]

Isn't netdev_legacy_api essentially the same as the new API in blocking mode? So it would be easier getting rid of that than to clutter the code of the synchronous netdevs (which I assume will always exist).