[PATCH 4/4] ASoC: wm8904: add DMIC support

[Pierluigi Passaro]

> > > > Just for my understanding, are you suggesting to set a device tree
> > > > property to force a fixed behavior in the driver ?

> > > Yes.

> > Why should we use a fixed behavior ?

> The things that are fixed by the design should be fixed.

> > > The device shares pins between the line inputs and the DMIC inputs so at
> > > least some of the configuration is going to be determinted at system
> > > design time, that will fix the usable values of at least one of the
> > > controls which ought to be reflected in the runtime behaviour.

> > In our design we use:
> > - pin 1: DMIC_CLK
> > - pin 24: LINEIN2R
> > - pin 26: LINEIN2L
> > - pin 27: DMIC_DATA

> > we have no pins shared among DMIC and LINEIN.

> This means that DMICDAT2 is not usefully selectable at runtime, you've
> got IN1 as digital and IN2 as analogue, so while the DMIC/ADC switch is
> useful the DMIC1/2 switch is not.

A customer could have the following working configuration
- pin 1: DMIC_CLK
- pin 24: LINEIN2R
- pin 25: DMICDAT2
- pin 26: LINEIN2L
- pin 27: DMICDAT1
with no shared pins: here there's the chance to select DMIC1, DMIC2 and
LINEIN2 at runtime: I can't find a reason for a fixed behavior.
Can you please elaborate ?