[Qemu-devel] OSS audio debugging

[Leigh Dyer <leigh@eclinic.com.au>]

Hi all,

I've been playing with the sb16 emulation using a Win2k guest. The Add
New Hardware wizard's hardware probe picked it up and installed it
without any problems, but playing audio quite often resulted in a very
abrupt end to the emulation.

I've tracked the problem down to the AUD_run() function in oss.c. When
writing to the card, it calls SNDCTL_DSP_GETOSPACE, which is apparently
meant to return the amount of data that can be written to the card
without blocking. However, for some reason, occasionally the value
returned in abinfo.bytes is negative. This negative value makes it
through to the write() call, which then fails with an unknown error,
hitting the:

ERRFail ("write audio");

line.

I really don't know much about OSS, so I'm not sure how this should be
handled. Does anyone else know what this could mean? For reference, the
card is an ess1371, running ALSA drivers in OSS emulation mode.

Thanks
Leigh