On Fri, 22 Oct 2010, Bensaid, Selma wrote:
Hi,
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
----- Jaroslav Kysela perex@perex.cz Linux Kernel Sound Maintainer ALSA Project, Red Hat, Inc.