VUB300 (USB wrapper for SDIO) how to?

I'm trying to use vub300 USB-to-SDIO. I have their evaluation board. The driver is already in the system, detects the plugged in chip right away:
$ dmesg | tail
. . . . .
ugen0.28: <Elan Digital Systems VUB300-1.20> at usbus0
However, nothing happens when I insert an SD card in its slot.
Also tried:
# kldload mmc
kldload: can't load mmc: module already loaded or in kernel
# kldload mmcsd
kldload: can't load mmcsd: module already loaded or in kernel
In Debian Linux it detects the SD card and creates an MMC device.

Thanks for ideas and directions!

[EDIT] I guess the driver is not in the system, I was wrong assuming that.
There is a driver source for Linux, not sure whether it can be ported easily.