Hi Michael
But nevertheless, shouldn't there be a check for a misconfiguration?
Yeah, maybe.
At least the bindings document should mention that this configuration is only valid for for the "scu" case. Oh and I've just had a look, the compatible string of this configuration is "simple-audio-card" in Documentation/devicetree/bindings/sound/simple-card.txt.
Between ourselves, historically, "scu" user was only me, and was used locally. At one point, "simple-audio-card" had been handled both, but noticed that it is impossible or will be super very complex. Because I was the only user of "scu", it is separated.
"scu" is for DPCM, but is covering only one part. It is not enough for generic use case...
Thank you for your help !! Best regards --- Kuninori Morimoto