Strange err=25 result.

[James Courtier-Dutton <James@superbug.demon.co.uk>]

Some debug output from calling snd_pcm_wait() when a USB device is 
unplugged.

(pcm_hw.c from /alsa-lib/src/pcm/pcm_hw.c)
file=pcm_hw.c:406 function=snd_pcm_hw_status err=25
pcm_hw.c: snd_pcm_hw_status() SNDRV_PCM_IOCTL_STATUS failed.

According to errno.h,
#define ENOTTY          25      /* Not a typewriter */

I would think that the following would be a better err result.
#define ENODEV          19      /* No such device */
or even
#define EPIPE           32      /* Broken pipe */

I have looked through alsa-lib and alsa-kernel and cannot find any place 
in the code that sets errno to 25!

Can anybody help?

My aim is to let the application detect when a usb audio device is 
unplugged, so that the application can release all alsa resources.
The application will then poll the alsa-lib trying to open the device 
again, and continually get errors until the audio usb device is plugged 
in again. For my application to achieve this, I would need a specific 
errno for the "usb device unplugged" that will not get confused with 
over/underruns or other errors that might not be "usb unplugged" related.

Cheers
James


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