Report to devlist as requested from USB-Audio.conf header:
1. all this headsets with windriver inf files + manual showing c-media driver must have the cm106x series 7.1 channel usb-codec in. there's no other from c-media for the design of 5.1 channel usb headsets available at this time, see:
http://www.cmedia.com.tw/?q=en/usb_audio
2. the headset interface shows up with 8 channels in lsusb -v , 1 8-ch pcm in /proc, and must be driven with surround7.1 pcm plug instead of surround5.1 or it will not work. speaker-test program works with -c6 -Dsurround7.1, test with -c8 works too, but shows that no SideL/R -speakers connected/routed/downmixed ( Speedlink Medusa 5.1 Mobile USB Headset, cm106L)
3. it works instantly without extra config using programs that allow specifying (-D)surround7.1 like VDR and MPlayer, VLC did not so far (maybe can do with special commandline) and therere maybe other unconfigurable (or buggy?) players that need a missing extra cm106 CARD configfile showing those apps a 5.1 channel device instead a 7.1.
i've done none so far, the config file language (especially routing and mappings) is not well documented, sorry.
y tom