Re: snd-firewire-ctl-services: Digidesign Digi-002R - missing control for 'Optical mode'

Hi,

On Mon, May 11, 2026 at 06:14:19PM -0400, [email protected] wrote:
> I have noticed that 'snd-firewire-ctl-services' does not provide a control
> for switching the mode of the Optical connections, which can be either ADAT
> or S/PDIF. The Windows/Mac drivers let the user select the mode.
> 
> It is mentioned in the kernel source, but seemingly not exposed to the user:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/sound/firewire/digi00x/digi00x-proc.c?h=v7.1-rc3#n34
> 
> Note, when 'Optical S/PDIF' is selected, the 'RCA S/PDIF' connectors are
> disabled.
> 
> I have the 002-Rack interface, and can assist with testing,
> Simon.

Yes. The service program provides no ALSA control element set
for this purpose, because Digi 002 differs from Digi 003 in how it
selects the source of S/PDIF signals for audio data in IEEE 1394
isochronous packets sent to the host system.

In my understanding, when the Digi 002 detects S/PDIF signals at the
optical input port, it automatically uses those signals for the packet
and ignores the S/PDIF signals in the coaxial input port. In contrast,
the Digi 003 allows the system software to select either the optical or
coaxial input as the source of S/PDIF signals when both are available.

However, I may have misunderstood the hardware behavior. Please let me
know if you observe any behavior that differs from my understanding
above.


Thanks

Takashi Sakamoto