Discover a microphone device, to later discover if it is receiving input

[info]

When Audacity uses ALSA, it somehow knows that something is a front mic.
In the total absence of documentation that I noted in my other email, 
how can I replicate this behaviour?
I do not insist on using hints. They were just mentioned somewhere on 
the Net. I am agreeable to use any methods in ALSA API to discover the 
mic, but w/o documentation, I have no way of knowing what it is, short 
of reverse engineering your library. Is this the way you envisioned 
adoption of ALSA: everyone is supposed to reverse-engineer?

Regards
Alex

On 2020-10-09 11:35 AM, Takashi Iwai wrote:
> Apart from the lack of the Input direction (maybe a bug in the hint
> code), the fundamental problem is that the driver cannot tell always
> the device type at all for each PCM stream.  It's simply because a
> stream may give you any input type depending on the mixer route; it's
> the case of HD-audio.  So, the same PCM device may be a mic, or a
> headset mic, or a line-in, or whatever.
>
> Sometimes there are dedicated PCM devices for certain inputs, but most
> of the PCM streams are generic purpose.
>
>
> Takashi
>