libasound-sndio

I started this toy project to replace libasound with sndio, as the PCM
plugin way seemed to always have problems in one way or another.
https://github.com/Cloudef/libasound-sndio (and eventually use tinyalsa in
sndiod instead of libasound, to get rid of userland alsa all together)

It works right now with SDL programs, dolphin-emu, PCSX2 at least. One of
the things I want to get work is wine. However, for some reason it seems
sio_write always returns 0 for wine programs, and I'm not sure what causes
this.

SNDIO_DEBUG=2 shows these 2 curious lines:
>libsndio: polls: 0, samples = 0
>aucat: start, maxwrite = 0

Before starting more indepth debugging, I thought I'd ask here if you have
any causes for sio_write returning zero.