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SC589-EZKIT as a USB audio source

I'm attempting to configure a SC589-EZKIT, running the Yocto build of Linux, to be a USB audio source & sink (UAC2) with configfs.  I can get the device to enumerate and play audio from the host, but returning isochronous audio back the host is eluding me.  The example in doesn't cover this mode, are there any other docs that cover it?