We have now fixed up mmap() problems with FreeBSD and OSS. You can run ossupdate and get the latest drivers. The mmap fixes are for Doom/Quake and the nonblocking i/o is for SDL/VLC.
Quake3 doesn't play properly on the HDA device. It works just fine on the SBLive and other devices we have. If you are using a virtual mixer
device to play quake, then you need to edit /usr/lib/oss/etc/options.cfg
and set softoss_rate=22050 (or whatever the rate is being requested
by the game). Then type rm /dev/dsp; ln -s /dev/dspXX /dev/dsp
where XX is a virtual mixer device (see ossinfo for list of devices)