[alsa-devel] [PATCH v3] ASoC: simple-card: add Device Tree support

[Mark Brown]

On Thu, Oct 24, 2013 at 06:17:59PM +0100, Mark Rutland wrote:
> On Fri, Oct 04, 2013 at 01:04:41AM +0100, Kuninori Morimoto wrote:

> > +- simple-audio,card-name		: simple-audio card name

> What's this used for?

This serves two useful functions.  One is that this is used for display
to users so they have a friendly name for the sound card (it is
relatively common to have multiple sound cards in the system).  The
other is that it is essentially a compatibility string for configuration
- you get a lot of sound devices that are electrically identical and
hence look the same from a driver point of view but due different
physical form factors should be configured differently.

> > +- format				: specific format if needed, see below
> > +- frame-master				: frame master
> > +- bitclock-master			: bitclock master
> > +- bitclock-inversion			: clock inversion
> > +- frame-inversion			: frame inversion

> What do these mean? Repeating the name without a dash is completely unhelpful.
> Describe what these imply.

These are all boolean propeties.  The meanings should be obvious or at
least very easily discoverable to anyone with any familiarity with audio
hardware; if you can understand what to do with them they should be OK.

> > +- clocks				: phandle for system clock rate

> Just one clock?

This is a limitation from the simple card, anything that needs more
complex clocking should be using a different binding.

> > +- system-clock-frequency		: system clock rate
> > +					  it will overwrite clocks's rate

> This seems very odd.

> Why do you want to overwrite a clock's rate?

It's relatively common to derive the audio clock from a general purpose
programmable clock which needs to be configured appropriately for use.

> > +simple-audio,format
> > +	"i2s"
> > +	"right_j"
> > +	"left_j"
> > +	"dsp_a"
> > +	"dsp_b"
> > +	"ac97"
> > +	"pdm"
> > +	"msb"
> > +	"lsb"

> What do these mean? Why are they not described when the property was defined above?

This is another one where the names should be clear for people familiar
with the hardware, they're well known terms.
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