ath10k FAQ

Kalle Valo kvalo at
Wed Apr 9 07:24:02 EDT 2014

Avery Pennarun <apenwarr at> writes:

> On Tue, Apr 8, 2014 at 3:41 AM, Kalle Valo <kvalo at> wrote:
>> I created a small FAQ to the wiki and added the four questions which
>> seem to be popular:
>> Comments welcome. And feel free to update it with new questions.
> This seems helpful.

Especially for me as now I can just answer with an URL ;)

> For the first question ("can't set channel") I think the provided
> answer is not the only cause of the problem, and was not the one that
> confused me at first. For me, the main confusion was that it's pretty
> non-intuitive how to set the 80 MHz center frequency in hostapd.conf
> ("the center frequency of the channel 6 higher than the lowest channel
> number in the 4-channel group"). It might help if you could include an
> example for that. I guess it varies by country so it might be a little
> tricky.

Good point. I tried to improve the answer a bit now:

Why I cannot start an AP in an 80 MHz channel / in 11ac mode?

If you get "nl80211: Failed to set channel" error from hostapd, most
likely that means that regulatory database doesn't support 80 MHz
channels (which were introduced in 11ac). You can check that with iw:

$ iw reg get
country FI: DFS-ETSI
        (2402 - 2482 @ 40), (N/A, 20)
        (5170 - 5250 @ 80), (N/A, 20)
        (5250 - 5330 @ 80), (N/A, 20), DFS
        (5490 - 5710 @ 80), (N/A, 27), DFS
        (57240 - 65880 @ 2160), (N/A, 40), NO-OUTDOOR

If you do not see "@ 80" within the frequency range you are using, it
means that the regulatory database doesn't support 80 MHz channels.

Other problem is that configuring VHT (= 802.11ac) in hostapd is not
very intuitive, pay extra attention how you configure it. Especially
vht_oper_centr_freq_seg0_idx is challenging. See example configuration
and hostapd configuration file documentation.

I'm trying to maintain all configuration related documentation in
respective pages and that's why I just have pointers in the FAQ.

Kalle Valo

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