hostapd and 11h support

[Arend van Spriel]

Hi Jouni,

I am looking at 11h support in hostapd. The supplicant uses 
.start_dfs_cac() driver callback (resulting in NL08211_CMD_RADAR_DETECT) 
and basically the CAC logic is done in the supplicant. Now for our 
devices the entire radar detection and CAC state machine is built in 
firmware. So hostapd would just need to enable 11h in the driver/firmware.

I am considering a new offload feature flag, but not sure whether we 
would need to introduce a new nl80211 command. I am thinking we could 
just reuse .start_dfc_cac(). Because of the feature flag it would have a 
different meaning in the driver. Wanted to know your opinion on this 
approach before starting the work.

Regards,
Arend