On Sun, 21 Jul 2002, Gary Scavone wrote:
> Yes, I know that you can determine the number of devices via the CTL
> interface ... that's what I use. But you cannot determine whether
> those devices support input and/or output without actually attempting
> to open them for playback or capture (please correct me if I'm wrong
> about this). So, if indeed you still need to open each device to
> determine its capabilities (input and/or output channels, etc...),
> then the previously mentioned error message should not be
> automatically written.
>
> Just to clarify, the device pcmC1D1c actually exists, as reported by
> the CTL interface. However, it only supports output, not input.
Use snd_ctl_pcm_info(). If stream is not available, -ENOENT is returned.
Don't forget to set device #, subdevice # and stream type before this call
(see snd_pcm_info_set_*() functions).
Jaroslav
> On Sat, 20 Jul 2002, Jaroslav Kysela wrote:
>
> >>On Fri, 19 Jul 2002, Gary Scavone wrote:
> >>
> >>>
> >>> ALSA lib pcm_hw.c:797:(snd_pcm_hw_open) open /dev/snd/pcmC1D1c failed:
> >>> No such file or directory
> >>>
> >>>
> >>> This message automatically gets output by the alsa library when you
> >>> call snd_pcm_open with SND_PCM_STREAM_CAPTURE on a device which can
> >>> only provide output (such as the second device of the ensoniq 1370).
> >>> Since you cannot probe a device's capabilities without opening it, it
> >>> seems to me that the library should not automatically print this
> >>> message to stderr (or stdout). Rather, the user can check the return
> >>> value of the call and get an error string if desired.
> >>>
> >>> The current behavior is very confusing.
> >>
> >>You can determine the number of PCM devices via the CTL interface.
-----
Jaroslav Kysela <[EMAIL PROTECTED]>
Linux Kernel Sound Maintainer
ALSA Project http://www.alsa-project.org
SuSE Linux http://www.suse.com
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