[iwn] Don't originate NULL data frames in net80211

[adrian]

Summary

Don't originate null data frames in net80211; leave that up to the
iwn firmware.

This should fix a bunch of cases where we're seeing out of sequence
802.11n aggregation data packets because net80211 power management
stuff was triggering NULL data frames when we don't need them and
messing up the firmware / ring buffer sequence number space.

[bz]

Based on your description it sounds more like you want to disable PS in net80211 and leave it to iwn?

[adrian]

In D52299#1194452, @bz wrote:

Based on your description it sounds more like you want to disable PS in net80211 and leave it to iwn?

(I thought I replied to this?)

It needs power saving configuration and queuing isn't a problem, but the firmware will implement the final gatekeeping as needed. net80211 can implement the buffering to the NIC if harsher PS is required.

In any case, the main source of the null frames is association/reassociating stuff and some scan start/stop stuff.

(And yeah, iwn should also be converted to full offloaded scan, now that I know how it works..)