If you want to use WDS on your WRT54g router, or other OpenWRT Kamikaze router, you MUST use the 2.4 broadcom version. If you do not see the WDS mode as an option in your wireless radio settings, double check that you are not running the 2.6 version of OpenWRT. The 2.6 version of OpenWRT Kamikaze is not yet compatible with WDS.

This thread is how I found out: http://forum.openwrt.org/viewtopic.php?id=19037