Support for scan while in AP mode, and offchannel while in AP mode

Kalle Valo kvalo at
Mon Aug 18 23:30:42 PDT 2014

Michal Kazior <michal.kazior at> writes:

> On 19 August 2014 08:07, Kalle Valo <kvalo at> wrote:
>> Avery Pennarun <apenwarr at> writes:
>>>>> Are there any plans to implement this feature?  It's important in
>>>>> order to implement automatic channel change in case of changes in the
>>>>> interference environment.
>>>> No plans at the moment. Does anyone know how much work would it be to
>>>> change mac80211 to support this with hw_scan?
>>> Is there any particular reason it can't just resort to a sw_scan for
>>> this use case?  What's the benefit of hw_scan?  I'm surprised there
>>> would be any particular CPU time taken for such a thing.
>> For mobile devices hw_scan is important because the ability to allow the
>> host CPU to sleep while scanning. For others I'm not that sure, maybe
>> firmware can do timing better (less intrusive) than host based sw
>> scanning?
> sw_scan requires a driver to be able to "just change the channel".
> Some device firmwares have no direct control over programmed hw
> channel. Instead they have start/join/connect commands that implicitly
> setup hw channel. ath10k is actually like that, isn't it (vdev start)?

Yes, my understanding as well is that the ath10k firmware is like that.
But I'm no firmware expert :)

I assume that the 10.x firmware does support hw_scan when in AP mode and
we would need to "just" change mac80211 to support that. But no idea how
big task that actually is.

Kalle Valo

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