Hi,

I'm studying a hardware implementation where an S/PDIF receiver is on the same I2S connection as codec. Essentially, the S/PDIF receiver echos the I2S capture data from the codec unless there is a digital input signal which it can lock on to. For playback, the I2S output from the CPU DAI goes directly to the codec.

I'm a bit at a loss for how to model this in ALSA. I know it's possible to have multiple codecs on a card, but those cases seem to be either separate codecs for the left and right channels, or separate codecs for capture and playback. In my case the playback codec is always the same, but the capture codec can switch between the two avilable input methods (more or less automatically if the S/PDIF receiver is so configured).

From a user perspective, it's not important that ALSA knows where the data

is actually coming from, so if I could just register the two "codecs" on the same dai_link at the same time it would be fine, but I'm just imagining that I'll run into problems when ALSA tries to set up streams with two different codecs being involved. (Of course, at some level, the user might be interested to know the signal routing, but that can be determined by reading appropriate status bits in the S/PDIF receiver for instance using amixer controls).

Do you have any ideas about how to configure this in ALSA?

/Ricard