after some more works, the following patch solved some issues for my dice saffire pro 40:
- avoid crashing/failed starting/missing inputs-outputs ports when starting jack with a samplerate different than the one in the rom.
- allow routing/mixer control (presently irrelevant) using ffado-mixer for pro 40 (and pro 24 ?).
Tested with a saffire pro 40 with 48kHz and 88.2 kHz, using Ardour, line/mic analog, and so on. ADAT and SPDIF not tested.
No changes for other dice devices (except correcting matrix mixer coefficients get/set).