I think I'm close to setup audio passthrough through HDMI. I would need someone who can test those passtrough modes. Any volunteer? Please write which modes you can test and which board do you have.
There are two things to consider:
1. kernel drivers treats samples as 24 bit but kodi as 16 bit. Probably 24 bit hack should be removed in kernel.
2. kernel patch linux-93-hdmi-fix-raw-output.patch might be needed, just remove ".disabled" from file extension to test