Hmm. Apart from some misleading documentation, that doesn't mention "GCD" at all, the logic seems odd.
In order to validate a new beacon interval, you're first looking up the min GCD value of all the combinations that allow the *current* scenario, but doing that matching without the right # of channels or radar detect parameters? And then you're trying to match that to the new beacon interval? It seems to me that the logic should be something like: If the driver specified diff_beacon_int_gcd_min, then don't do anything in cfg80211_validate_beacon_int(), other than perhaps a minimal range check against the minimum of all diff_beacon_int_gcd_min values for all combinations. Then, add a new argument to cfg80211_check_combinations() (and cfg80211_iter_combinations()) to have the beacon intervals for each beaconing interface, and use that in order to match if a combination fits, inside cfg80211_iter_combinations(). That new argument could be made the GCD of all existing beaconing interfaces (or 0 if no such exists), since that's sufficient for checking against a new min_gcd. johannes
