vht_capab reading 0x0 but `iw list` says otherwise

[Krishna Chaitanya]

On Wed, Oct 14, 2015 at 11:04 PM, James Sumners <james.sumners at gmail.com> wrote:
>
> When I launch hostapd I see a line in the log that reads "hw vht capab:
> 0x0, conf vht capab: 0x0". That is accurate because I currently have no
> `vht_capab` line defined in my configuration. However, if I do an `iw
> list` on my device then I see the following list of capabilities:
>
> ```
> VHT Capabilities (0x038071a0):
>   Max MPDU length: 3895
>   Supported Channel Width: neither 160 nor 80+80
>   short GI (80 MHz)
>   TX STBC
>   SU Beamformee
> VHT RX MCS set:
>   1 streams: MCS 0-9
>   2 streams: MCS 0-9
>   4 streams: not supported
>   ...
>   8 streams: not supported
> VHT RX highest supported: 0 Mbps
> VHT TX MCS set:
>   1 streams: MCS 0-9
>   2 streams: MCS 0-9
>   4 streams: not supported
>   ...
>   8 streams: not supported
> VHT TX highest supported: 0 Mbps
> ```
>
> When I set my hostapd config to have the line
> `vht_capab=[SHORT-GI-80][TX-STBC-2BY1][SU-BEAMFORMEE]` then I get
> an error that "SHORT-GI-80" is not supported. I can remove each
> capability from the configuration directive and get the same sort of
> result.
>
> When I set `vht_oper_chwidth=1`, without setting `vht_capab`, then I
> get an error:
>
> ```
> Mode: IEEE 802.11g Channel: 4 Frequency: 2427 MHz
> DFS chan_idx seems wrong; num-ch: 13 ch-no: 36 conf-ch-no: 4 11n: 1
> sec-ch: 0 vht-oper-width: 1
> // list of channels available - [1, 13]
> ```
>
> If I set `vht_oper_chwidth=0`, still without `vht_capab` set, then I
> get an error:
>
> ```
> Mode: IEEE 802.11g Channel: 4 Frequency: 2427 MHz
> DFS 0 channels required radar detection
> Could not set channel for kernel driver
> ```
>
> If I set `ieee80211ac=0` then hostapd starts up correctly (no other
> changes to the configuration).
>
> My card is an Intel 7260 that supports both AP and "AP/VLAN" modes with
> one BSSID. I am using the nl80211 driver (i.e. `driver=nl80211` in
> hostapd.conf).
>
> Do you have any suggestions as to what could be wrong with my setup?
>
It looks like you are trying to use VHT in 2.4GHz.
Can you past the full config? is your hw_mode set to a to use VHT?