On Fri, Oct 27, 2017 at 04:47:20PM +0200, Mark Kettenis wrote: > I don't know, but with the ioctl removed, there is nothing that sets > the IEEE80211_F_QOS flag anymore. That seems weird.
This flag is just unused for now. It is a left-over from unfinished 11n support code by damien. But I expect that it will be useful. A-MPDU frames (sent with Tx aggregation) are QoS frames. So we're not sending QoS frames yet, we are just receiving them. The receiving code path can detect QoS by checking for QoS headers in received frames, which works without a flag. But the flag is already wired up in some of the Tx logic, and I expect the F_QOS flag will eventually be used as part of a Tx agg implementation. It could be set by drivers in order to enable QoS and thus advertise A-MPDU Tx support to net80211 (there is no good reason for using QoS without 11n). The stack then knows that it needs to supply QoS frame headers, and can provide a Tx subframe re-ordering buffer for drivers for cases where firmware doesn't provide one.
