MIDI handshake for Pioneer DJ DJM-250MK2 to enable recording LINE/PHONO channels

[František Kučera]

Dne 19. 01. 21 v 9:54 Takashi Iwai napsal(a):
> I haven't looked closely, but if it's about MIDI messaging, it can be
> implemented in the kernel, too (only if it fits better than
> user-space), yes.  If it's over HID, it's a different story, though.

Yes, it is only MIDI. The scenario is:

1) send a greeting message to the mixer

2) receive a greeting message

3) send another constant message

4) receive the response

5) compute something and send it back

6) receive the confirmation message

7) start sending a keep-alive message each 200 ms

Specific received messages might be consumed by kernel (invisible for user-space), but others should flow undisturbed to the user-space. The sent messages should be injected and intermixed with normal messages coming from user-space. The kernel should not claim exclusive access to the MIDI device, because user-space tools might want to use it too.

Is there already anything similar, for inspiration?

Franta