Johannes Berg <johannes@xxxxxxxxxxxxxxxx> writes: > On Fri, 2019-10-18 at 15:31 +0200, Toke Høiland-Jørgensen wrote: > >> Well, let's try to do the actual math... A full-size (1538 bytes) packet >> takes ~2050 microseconds to transmit at 6 Mbps. Adding in overhead, it's >> certainly still less that 4096 us, so 12 bits is plenty. > > What about A-MSDUs? But I guess maximum continous transmissions are at > most 4ms anyway, so a single packet should never be longer. Ah yeah, those could be a bit bigger, but yeah, 4ms should at least be enough. >> That leaves >> four bits for the ACK status ID if we just split the u16; if we only >> ever have "a handful", that should be enough, no? > > It's how many are in flight at a time, 16 doesn't seem likely to happen, > but I don't really know what applications are doing with it now. > Probably only wpa_s for the EAPOL TX status. Right. Well in that case, let's try it. As long as we fail in a reasonable way, we can just see if we run into anything that breaks? I guess in this case that means rejecting requests from userspace if we run out of IDs rather than silently wrapping and returning wrong data :) >> We could also split 5/11. That would support up to 32 ACK IDs, and we >> can just truncate the airtime at 2048 us, which is not a big deal I'd >> say. > > We can also play with the units of the airtime, e.g. making that a > multiple of 2 or 4 us? Seems unlikely to matter much? Sure, that's a good point! Increments of 4us means we can fit 4ms is 10 bits, leaving plenty of space for ACK IDs (hopefully). I'll rework the series to use that instead :) -Toke
