kern/54264: audio(4) API fails to detect a capture-only device

[nia%netbsd.org@localhost]

>Number:         54264
>Category:       kern
>Synopsis:       audio(4) API fails to detect a capture-only device
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Jun 02 13:35:00 +0000 2019
>Originator:     Nia Alarie
>Release:        NetBSD 8.99.42
>Organization:
>Environment:
>Description:
I'm testing with a USB microphone, which is /dev/audio1.

First I query the device with AUDIO_GETPROPS.  It claims that the
device has playback support.  This is incorrect.

Then I query the device with AUDIO_GETFORMAT, which only fills the
record struct with valid data, and fills the playback struct with
garbage.

Currently, I can't figure out how to detect a USB microphone other
than by hoping that the garbage in the prinfo struct is out of range.
>How-To-Repeat:
>Fix: