Can anyone point me in the direction of the code that controls the supported rates advertised in beacons coming from an openWrt AccessPoint?

I'm running OpenWRT 8.09 (mac80211). When I capture the beacons coming from my Access Point I can see the list of supported rates.  But when I try to change them using the basic_rate option to 'wifi-device', there is no change.  The beacons come out with the same list of supported rates.

I was hoping I could do this by simply changing the configuration but I'm starting to give up on that so now I'm looking to the source code.  (of course there must be a way; it's unthinkable -isn't it- that it would be impossible to change advertised rates in openWRT ...right?)