Re: [PATCH v7 2/2] ASoC: fsl: Add S/PDIF machine driver

[Mark Rutland <mark.rutland@arm.com>]

On Mon, Aug 19, 2013 at 10:50:43AM +0100, Nicolin Chen wrote:
> Hi,
> 
> On Mon, Aug 19, 2013 at 10:24:58AM +0100, Mark Rutland wrote:
> > Is this used semantically, or is it a completely arbitrary string?  In
> > either case I don't see why the compatible string doesn't give the
> > driver enough to have a sensible value.
> > 
> > I'm confused as to why we need this. The phrase "user-visible" in a
> > device description seems very odd.
> 
> The string would be in the ALSA device list:
> ALSA device list:
>   #0: imx-spdif
> 
> I think it can be a sort of arbitrary as long as users know which this 
> device exactly is when they catch the name by 'aplay -l' or 'arecord -l'
> 
> The phrase "user-visible" is being used in many current docs, I don't 
> dare to change it unless a sage gives me a suggestion.

I can see that there is entrenched usage, but this really seems to be
embedding Linux-specific implementation details into the dt. I don't see
why the driver cannot select a sensible name, but perhaps I'm missing
something.

Mark, is there any reason we need to handle the user-visible name of the
device this way?

> 
> > > +
> > > +  - spdif-controller : The phandle of the i.MX S/PDIF controller
> > > +
> > > +
> > > +Optional properties:
> > > +
> > > +  - spdif-transmitter : The phandle of the spdif-transmitter dummy codec
> > > +
> > > +  - spdif-receiver : The phandle of the spdif-receiver dummy codec
> > > +
> > > +* Note: At least one of these two properties should be set in the DT binding.
> > 
> > Are all four units (comlpex,controller,transmitter,receiver) really
> > separate blocks?
> 
> At least they are separate drivers as I mentioned in the commit comments.

I'm not sure that the boundary of Linux drivers should necessarily
determine the way we carve up the description of IP blocks, though
presumably it's a pretty sensible way of carving it up or we wouldn't
have done it.

Is there any public documentation on the i.MX S/PDIF hardware block(s)?

Thanks,
Mark.