[alsa-devel] [PATCH] ASoC drivers for the Freescale MPC8610 SoC

Grant Likely grant.likely at secretlab.ca
Thu Jan 3 19:25:45 CET 2008

On 1/3/08, Timur Tabi <timur at freescale.com> wrote:
> Grant Likely wrote:
> > Does that mean with ASoC V2 you can instantiate it with the board
> > specific platform code instead?
> I don't know.  I haven't really looked at V2 yet.  You'll have to ask Liam
> Girdwood.
> > This is one of the examples of where the compatible properties are
> > trying to be far to generic about what they are.  How do you define
> > what "fsl,ssi" is?
> The SSI is a specific Freescale device, so I think it's pretty well defined.
> > What happens when Freescale produces another
> > peripheral that can do ssi but isn't register level compatible?
> It won't be called the SSI.  It will be called something else.

Heh, I've seen enough to know that it's virtually impossible for a
company to maintain a consistent naming scheme all the time.  Better
to be specific now and add generic names sometime in the future rather
than the other way around.

> > In my opinion, it is far better to be specific in the device tree and
> > teach the driver about what versions it is able to bind against.  In
> > this case, I would use "fsl,mpc8610-ssi" or maybe better yet:
> > "fsl,mpc8610-ssi,i2s" (MPC8610 SSI device in I2S mode).
> I can work with that, but the SSI could be placed into any future 83xx, 85xx,
> or 86xx SOC, and the driver will still work with it as-is.

The have the device trees claim compatibility with the older
fsl,mpc8610-ssi device specifically.  ie: compatible =
"fsl,mpc83<whatever>-ssi,ac97", "fsl,mpc8610-ssi,ac97";

> > I don't like the idea of a separate fsl,mode property to describe the
> > behaviour of multifunction peripherals.  It makes probing more
> > difficult when there is a different driver for each mode.
> Can you propose an alternative?  The driver needs to know what mode to use
> when communicating with its codec.  How am I supposed to know if I have an I2S
> codec or an AC97 codec?

Make the compatible property tell you!  :-)  If it's connected to an
I2S codec, then it could be compatible = "fsl,mpc8610-ssi,i2s".  Or
for AC7, compatible = "fsl,mpc8610-ssi,ac97"


Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.
grant.likely at secretlab.ca
(403) 399-0195

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