On 4/11/21 3:14 AM, Peer, Ilan wrote:
Hi Ben,
-----Original Message-----
From: Ben Greear <greearb@xxxxxxxxxxxxxxx>
Sent: Wednesday, March 31, 2021 15:04
To: Luca Coelho <luca@xxxxxxxxx>; kvalo@xxxxxxxxxxxxxx
Cc: linux-wireless@xxxxxxxxxxxxxxx
Subject: Re: [PATCH 06/12] iwlwifi: mvm: Add support for 6GHz passive scan
On 3/31/21 2:14 AM, Luca Coelho wrote:
From: Ilan Peer <ilan.peer@xxxxxxxxx>
When doing scan while 6GHz channels are not enabled, the 6GHz band is
not scanned. Thus, if there are no APs on the 2GHz and 5GHz bands
(that will allow discovery of geographic location etc. that would
allow enabling the 6GHz channels) but there are non collocated APs on
6GHz PSC channels these would never be discovered.
To overcome this, FW added support for performing passive UHB scan in
case no APs were discovered during scan on the 2GHz and 5GHz channels.
Add support for enabling such scan when the following conditions are
met:
- 6GHz channels are supported but not enabled by regulatory.
- Station interface is not associated or less than a defined time
interval passed from the last resume or HW reset flows.
- At least 4 channels are included in the scan request
- The scan request includes the widlcard SSID.
- At least 50 minutes passed from the last 6GHz passive scan.
Why are you trying so hard to not do passive scans? This seems like it is set
up for all sorts of frustration.
This logic enables a special 'passive' scan which is not directly intended for discovery of APs for connection etc. but
for discovery of APs with country information in the beacons/probe responses, so the fw could use this information
as an input that might allow it to enable 6GHz channels (which are supported but are disabled). This special scan
is intended for cases that the device does not have any other regulatory information that allows it to enable the 6GHz channels.
Once these channels are enabled, we use passive scan as needed.
We generally try to avoid passive scan on all the 6GHz channels as this is a long flow that takes at least 6 seconds (as there are
such 64 channels) and with the discovery mechanisms defined for the 6GHz is not really needed.
If the station comes up and does a 6E passive scan and does not find any AP, perhaps because 6Ghz AP was turned on 1 minute after the station
tried to initially scan, this means that it will take 50 minutes before it can have a chance to scan
the AP and connect to the Internet? If station cannot connect after a relatively short time,
then I think it should scan as widely as it can in order find some possible way to connect.
And why care about 'at least 4 channels'. If we know the AP channel, and can scan exactly there, then your
concern about taking a long time is resolved.
How else can we tell the radio that 6E is allowed? I previously tried all sorts of things
to enable 6E channels so that I could more easily set the radio to sniff one of those channels
in monitor mode, and I had no luck.
If all of the 6E channels are marked as passive, what harm is it to enable the channels
in the regdom from the beginning?
Thanks,
Ben
Hope this clarifies things.
Regards,
Ilan.
--
Ben Greear <greearb@xxxxxxxxxxxxxxx>
Candela Technologies Inc http://www.candelatech.com
