+// This test will iterate over all cards detected in the system, exercising
would it make sense to test only specific cards? People doing automated tests might have a USB device for capture of analog loopbacks, or injection of specific streams for capture, and usually care about testing such devices - which do need manual setups and wiring btw.
It's not really idiomatic for kselftest to require any per system configuration by default - half the thing is that you can just run it and it should do as much as it can sensibly on the system. You could definitely add some command line options for development or manual usage though.
I was thinking of adding this test to our CI, it's a bit orthogonal to self-tests indeed. IIRC we check that we can modify all the PGA settings for volume control but this test is a lot more generic.