via vt8233a spu problems, 5.1r (bug?)

Dear mailing list,
I am new to you so please disregard some possibly wrong form of posting.
Actually I am using a FreeBSD 5.1-release system provided by an iso-
image I downloaded on Sun Nov 30 with a self-compiled kernel. I added
options pcm in order to be able using my onboad vt8233a chipset.
Sound works but even when letting xmms play its playlist I get
some error sort of "Check
you have the correct output plugin selected,
no other programs is blocking the soundcard,
your soundcard is configured properly". Seems as if xmms would block 
itself.
If I double-click on the tracklist item it sometimes works again, sometimes
it doesn't. I thought setting an appropiate vchans value (3?) via sysctl
could help.. But that isn't the case. Also when I play some movie with 
mplayer
and seek a bit back and forth or so either xmms or mplayer would quit! 
mplayer
would then say:
"Fatal error: *** CANNOT RE-OPEN / RESET AUDIO DEVICE *** Operation not
supported by device"
I already tried a value of 8 for hw.snd.maxautovchans and 
hw.snd.pcm0.vchans
but that makes no difference.
I remember that such bug didn't exist in 4.7 and 4.8. I switched to netbsd
in the past and it had some bug either. I met someone who was working on
backportpatches or something of the current via driver on irc who couldn't
find out what the problem was.. I partially remember that I was told that
it had something to do with the initialization code of the driver because
after an update to current it wasn't working until I powered-down the
system. I don't think that the one who told me that was the same person
working on those backport patches so that information was unnecessary ^^
Anyways I assume it has something to do with the driver because of my past
experience that full support for this chip yet seems to be under 
development.
Thanks for audience.

Maybe useful listings:

core diff of:
"src/sys/dev/sound/pci/via8233.c,v 1.10 2003/04/17 15:04:11 orion"
compared against:
"src/sys/dev/sound/pci/via8233.c,v 1.13 2003/09/02 17:30:37 jhb"

<       via->regid = PCIR_MAPS;
---
>       via->regid = PCIR_BAR(0);
795c795,796
<               /*flags*/0, &via->parent_dmat) != 0) {
---
>               /*flags*/0, /*lockfunc*/busdma_lock_mutex,
>               /*lockarg*/&Giant, &via->parent_dmat) != 0) {
811c812,813
<               /*flags*/0, &via->sgd_dmat) != 0) {
---
>               /*flags*/0, /*lockfunc*/busdma_lock_mutex,
>               /*lockarg*/&Giant, &via->sgd_dmat) != 0) {

(I don't understand how to backport by myself and test^^
Maybe someone wants to do that for me :D?)

# dmesg | grep VT8223:
pcm0: <VIA VT8233A> port 0xc400-0xc4ff irq 11 at device 17.5 on pci0