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

Avery Pennarun apenwarr at
Mon Aug 18 22:56:35 PDT 2014

On Tue, Aug 19, 2014 at 1:50 AM, Kalle Valo <kvalo at> wrote:
> Avery Pennarun <apenwarr at> writes:
>> In the ath9k and several other drivers, commands like the following
>> work while in AP mode:
>>   iw wlan0 scan -u ap-force passive
>> and
>>   iw wlan0 offchannel 2452  100
>> On ath10k (using a driver from v3.15-rc1 as of April 13th), these tell
>> me the operation is not supported.
> Yeah, mac80211 only supports this with sw_scan but ath10k uses hw_scan.
> From ieee80211_alloc_hw():
>         if (!ops->hw_scan)
>                 wiphy->features |= NL80211_FEATURE_LOW_PRIORITY_SCAN |
>                                    NL80211_FEATURE_AP_SCAN;
>> 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.



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