Bitstreaming on linux works on USB only.
There are no system drivers for ALSA bitstreaming over HDMI that I'm aware of. Hendrik would know for sure.
Your audio device must support DSD_U32_BE
run
/usr/lib/jriver/Media\ Center\ 31/alsacap
from a terminal prompt and look for your device.
Card 1, ID `AudioDOP2', name `iFi (by AMR) HD USB Audio (DOP2'
Device 0, ID `USB Audio', name `USB Audio', 1 subdevices (1 available)
2 channels, sampling rates 44100, 48000, 88200, 96000, 176400, 192000, 352800, 384000 Hz
Sample formats: S32_LE, SPECIAL, DSD_U32_BE
Subdevice 0, name `subdevice #0'
Also, use a HW: device.
If you device supports native DSD (as opposed to DoP) you can set that in audio device settings.