M-Audio Fast Track Ultra S/PDIF clock source

[George Marques]

Hello, I have my trusty old FTU audio interface and I've been super happy
of how it works well on Linux with ALSA.

Today I finally found some use for the S/PDIF input, which would allow me
to free up two analog inputs in my setup. However, I found out it's not
possible to change the clock source using ALSA, so I cannot use the S/PDIF
input on Linux.

This issue was raised by Felix Homann back in 2011:
https://www.alsa-project.org/pipermail/alsa-devel/2011-June/040846.html but
I couldn't find any new development, even though other issues were fixed.

On Windows the proprietary driver naturally has an option for that, which
allowed me to verify that the input is in fact working correctly. Changing
on Windows and then rebooting into Linux does not work, so either this is
not persisted or something on Linux is unknowingly changing it back.

I actually want to help add this option to the driver, so I can use it
myself but also make it available to others who still rely on this
interface.

My questions are:

1) Was there any progress in this regard? Most of work has been done around
2012 for what I could find, nothing newer, so can I assume no work was done
after the concern was raised?

2) If I were to develop this option, where could I start? I can get myself
around with C, but I have no idea how to debug and test my patches, nor how
to find the exact control.

I know it's an old card, but it works very well for me so I have no excuse
to just replace it at this point.

I hope someone can help me.