MAN301 internal routing (Re: [PATCH] ALSA: dice: add stream format parameters for Weiss devices)

[Takashi Sakamoto <o-takashi@sakamocchi.jp>]

Hi Michele Perrone, Michele Perrone,

I restart my work to support Weiss models[1] as I have enough time after
some tasks. After implementing control elements for your MAN301, I have
some questions about internal routing. Would I ask your advices about
them?

I think the model has below inputs/outputs.

* inputs
   * spdif-opt-input-1/2
   * spdif-coax-input-1/2
   * aesebu-xlr-input-1/2
   * stream-input-1/2
* outputs:
   * stream-output-1/2
   * spdif-coax-output-1/2
   * aesebu-xlr-output-1/2
   * analog-xlr-output-1/2
   * analog-coax-output-1/2

And at present I guess its internal routing is like[2]:

```
spdif-opt-input-1/2  ---+
spdif-coax-input-1/2 --(or)--> digital-input-1/2 -----------------> stream-output-1/2
aesebu-xlr-input-1/2 ---+             |
                                      v
stream-input-1/2 --------------------(or)--+----------------------> spdif-coax-output-1/2
                                           +----------------------> aesebu-xlr-output-1/2
                                           +--analog-output-1/2 --> analog-xlr-output-1/2
                                                      +-----------> analog-coax-output-1/2
```

Then I have some questions.

1. The signal source designated for stream-output-1/2
I think it is any type of digital input designated by control element
"Digital Input Capture Route", or source ID block which generates
silence.

2. The signal sources designated for the outputs
According to the manual of MAN301, the sources are selectable somehow.
There are two ways at least for pre-amp and player modes. I guess that
any interface is defined to configure internal router for the purpose.

[1] https://github.com/alsa-project/snd-firewire-ctl-services/tree/topic/weiss-support
[2] https://github.com/alsa-project/snd-firewire-ctl-services/blob/topic/weiss-support/protocols/dice/src/weiss/avc.rs#L12


Thanks

Takashi Sakamoto