from package/madwifi/Makefile:

MADWIFI_AUTOLOAD:= \
        wlan \
        wlan_scan_ap \
        wlan_scan_sta \
        ath_hal \
        ath_rate_$(RATE_CONTROL) \
        wlan_acl \
        wlan_ccmp \
        wlan_tkip \
        wlan_wep \
        wlan_xauth

ifeq ($(findstring AHB,$(BUS)),AHB)
        MADWIFI_AUTOLOAD += "ath_ahb countrycode=276"
endif
ifeq ($(findstring PCI,$(BUS)),PCI)
        MADWIFI_AUTOLOAD += ath_pci
endif