results.
Right now the scan infrastructure assumes the channel is under net80211
control, and that when receiving beacon frames for scanning, the
current channel is indeed what ic_curchan is set to.
But firmware NICs with firmware scan support need more than this -
they can do background scans whilst hiding the off-channel behaviour
from net80211. Ie, net80211 still thinks everything is associated
and on the main channel, but it's getting scan results from all the
background traffic.
However sta_add() pays attention to ic_curchan and discards scan
results that aren't on the right channel. CCK beacon frames can be
decoded from adjacent channels so the receive path and sta_add
discard these as appropriate. This is fine for software scanning
like for ath(4), but not for firmware NICs. So with those, the
whole concept of background firmware scanning won't work without
major hacks (eg, overriding ic_curchan before calling the beacon
input / scan add.)
As part of my scan overhaul, modify sta_add() and the scan_add()
APIs to take an explicit current channel. The normal RX path
will set it to ic_curchan so it's a no-op. However, drivers may
decide to (eventually!) override the scan method to set the
"right" current channel based on what the firmware reports the
scan state is.
So for example, iwn, rsu and other NICs will eventually do this:
* driver issues scan start firmware command;
* firmware sends a "scan start on channel X" notify;
* firmware sends a bunch of beacon RX's as part of
the scan results;
* .. and the driver will replace scan_add() curchan with channel X,
so scan results are correct.
* firmware sends a "scan start on channel Y" notify;
* firmware sends more beacons...
* .. the driver replaces scan_add() curchan with channel Y.
Note:
* Eventually, net80211 should eventually grow the idea of a per-packet
current channel. It's possible in various modes (eg WAVE, P2P, etc)
that individual frames can come in from different channels and that
is under firmware control rather than driver/net80211 control, so
we should support that.
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