[alsa-devel] Question regarding snd_pcm_control_ioctl
perex at perex.cz
Fri Oct 22 10:56:34 CEST 2010
On Fri, 22 Oct 2010, Bensaid, Selma wrote:
> I have question concerning ALSA Core snd_pcm_control_ioctl function.
> I have noticed that the IOCTL fails if it's called for a device with
> substream_count = 0, since I'm implementing a PCM device that supports
> Record and does not support Playback, the IOCTL fails when called for
> the Playback stream. I would propose, in such case, to return that the
> stream has 0 playback substreams instead of failing.
You mean probably that the SNDRV_CTL_IOCTL_PCM_INFO ioctl returns -ENOENT
when an invalid direction is accessed. It looks correct to me. If
a direction does not exist, it makes no sense to gather info for it. And
-ENOENT response clearly shows that this direction is not available, so
the user space tools can distict if it's an unexpected error or this one.
Jaroslav Kysela <perex at perex.cz>
Linux Kernel Sound Maintainer
ALSA Project, Red Hat, Inc.
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