Made up a summary of all the issues with the telephony drivers and sent it off. Now I'm waiting for a reply, and have ended up debugging sound drivers instead. select(2) (and obviously poll(2)) breaks in interesting and different ways on different drivers. Somehow I am not surprised.
On a related subject, the VIA PLE133 chipset is really crap, and I suggest avoiding it. The integrated video won't do over 1024x768 without massive noise in the image, and the on-board audio uses one of those lame-o AC97 codecs that only does 48kHz. Suck.
Of course, if people who wrote sound applications actually knew that SNDCTL_DSP_SPEED returns a meaningful value in its argument (in particular the people who wrote the OSS backend for libao), that would also be helpful.
I guess I should probably just install ALSA on that box since its library will do all the necessary sample conversion. The kernel's VIA audio driver is really nice otherwise though, so I kind of fear what might happen.
In general, though, ALSA seems to have evolved to the point where it does a better job of OSS audio than the actual OSS modules. This is fairly impressive.