2021-08-20 16:44:39

by Ben Greear

Subject: CAC question: DFS -> non-dfs -> DFS

Hello,

While poking at the MTK driver and trying to fix some CAC bugs in it,
I noticed the following:

Select ch 100, which enables DFS CAC logic. Wait for that to finish.
Then select CH 36 (disable DFS)
Then select ch 100 again, and the chandef->chan->dfs_state is set back to 0
which I think means we must do CAC again.

I was expecting in this case that the DFS state would be set to NL80211_DFS_AVAILABLE
instead, since CAC just passed a few minutes prior?

Thanks,
Ben

--
Ben Greear <[email protected]>
Candela Technologies Inc http://www.candelatech.com

2021-08-29 17:57:25

by Janusz Dziedzic

Subject: Re: CAC question: DFS -> non-dfs -> DFS

pt., 20 sie 2021 o 18:45 Ben Greear <[email protected]> napisał(a):
>
> Hello,
>
> While poking at the MTK driver and trying to fix some CAC bugs in it,
> I noticed the following:
>
> Select ch 100, which enables DFS CAC logic. Wait for that to finish.
> Then select CH 36 (disable DFS)
> Then select ch 100 again, and the chandef->chan->dfs_state is set back to 0
> which I think means we must do CAC again.
>
> I was expecting in this case that the DFS state would be set to NL80211_DFS_AVAILABLE
> instead, since CAC just passed a few minutes prior?
>

This depends on DFS region (country).
EU allow preCAC - once you pass CAC then you can switch to other
channel and - the old one will be DFS_AVAILABLE - no need to do CAC
again.
All other regions don't allow preCAC - so each channel switch will
clear DFS_AVAILABLE and require CAC again.

BR
Janusz