Just grabbed the ALSA sources, grep -i -r "echoaudio" and you get a folder /alsa-kernel/pci/echoaudio/.
In there there's a indigoiox.c file, which seems to contain code to make it work. I'm not an ALSA dev, but I'd be confident enough with that info that its all good. Otherwise at least you know where to start whining to get support ;)
Enjoy! -Harry