Any issues with GETOSPACE OSS ioctl?

Any issues with GETOSPACE OSS ioctl?

[Timur Tabi]

I have a customer who reports that when his OSS application makes several
write() followed by SNDCTL_DSP_GETOSPACE, the returned value is not decreasing,
which implies that the write() commands are not going through.

I've looked at the OSS documentation for this ioctl
(http://manuals.opensound.com/developer/SNDCTL_DSP_GETOSPACE.html), and it
implies that it is not reliable.  But since the customer is using ALSA (i.e.
ALSA's OSS emulation), I don't know if that applies.

So I'd like to know how the 'bytes' return value is calculate in ALSA.

-- 
Timur Tabi
Linux kernel developer at Freescale

Re: Any issues with GETOSPACE OSS ioctl?

[Clemens Ladisch]

Timur Tabi wrote:
> I have a customer who reports that when his OSS application makes several
> write() followed by SNDCTL_DSP_GETOSPACE, the returned value is not decreasing,
> which implies that the write() commands are not going through.

When write() doesn't return an error, it succeeded.

The GETOSPACE return value does not decrease as long as the written data
has not yet filled an entire fragment.  (This behaviour can be changed
with the partial-frag option; see
linux/Documentation/sound/alsa/OSS-Emulation.txt).


HTH
Clemens