[alsa-devel] ASoC: Device tree binding to dummy codec

[jonsmirl at gmail.com]

Allwinner CPUs have an on-chip codec that supports line out. This is a
monolithic block that does not implement anything like standard I2S.
We have implemented this by internally making a soc_card and then
binding the DAI to a dummy NOP codec to make ASoC happy.

But now someone wants to add a MAX9768 amplifier which needs a codec
driver to implement volume control.

So how should this be implemented? You want to use simple-audio-card
when the MAX9768 is present.

But what about the dummy-codec case? Using simple-audio-card to bind
to a dummy-codec clutters things up a lot. Plus the dummy-codec is not
currently exposed to device trees.

And then there is the ordering problem, how do I know for sure MAX9768
is not going to be bound so that it is safe to bind to dummy-codec.
Or should binding to MAX9768 simply override a binding to the
dummy-codec?

If my dummy-codec is exposed into the device trees then this generates
a bunch of NOP clutter in the tree using simple-audio-card to bind it.

Another idea, maybe one of those NOP SDPIF codecs could get an alias
name like NOP or Dummy.

-- 
Jon Smirl
jonsmirl at gmail.com