Comment 29 for bug 1498129

Raymond I have done that. Also today I was able to test an Asus Xonar U7 but the edition of the card which is not the Echelon edition. I believe the two cards are the same hardware but the echelon edition had additional Windows software included and for some reason Asus decided to change the USB name

This non-Echelon version presents itself as "Xonar U7" to alsa and adding '"Xonar U7" 1' to USB-Audio.pcm.iec958_device appears to work as

aplay -L | grep -A 2 iec958

reports

iec958:CARD=U7,DEV=0
    Xonar U7, USB Audio #1
    IEC958 (S/PDIF) Digital Audio Output

I still wasn't able to play directly from it - I guess I need to do further work in pulseaudio too. I can't test that as I only had the card on loan but will progress this once alsa-devel have a fix for the '.' in my own Echelon card name