Re: [RFC PATCH 2/3] pinctrl: at91: add support for generic pinconf

[boris brezillon]

On 27/08/2013 05:57, Stephen Warren wrote:
> On 08/26/2013 11:17 AM, boris brezillon wrote:
> > On 26/08/2013 18:53, Stephen Warren wrote:
> > > On 08/24/2013 03:37 PM, Boris BREZILLON wrote:
> > > > Add support for generic pin configuration to pinctrl-at91 driver.
> > > > diff --git
> > > > a/Documentation/devicetree/bindings/pinctrl/atmel,at91-pinctrl.txt
> > > > b/Documentation/devicetree/bindings/pinctrl/atmel,at91-pinctrl.txt
> > > >    Required properties for iomux controller:
> > > > -- compatible: "atmel,at91rm9200-pinctrl"
> > > > +- compatible: "atmel,at91rm9200-pinctrl" or "atmel,at91sam9x5-pinctrl".
> > > You seem to also be adding a second chip name to the list here, which is
> > > more than the patch subject/description imply you're doing...
> > This is an update of the documentation:
> > "atmel,at91sam9x5-pinctrl" compatible is already used in the pinctrl
> > driver but the documention
> > was not updated.
> >
> > But I agree, this should not be part of this series.
> >
> > > > +  Add "generic-pinconf" to the compatible string list to use the
> > > > generic pin
> > > > +  configuration syntax.
> > > "generic-pinconf" is too generic of a compatible value for this binding
> > > to define.
> > >
> > > Instead, I think you want to either:
> > >
> > > a)
> > >
> > > Use compatible="atmel,at91rm9200-pinctrl" for the old binding,
> > > use compatible="atmel,at91rm9200-pinctrl-generic" for the new binding
> > >
> > > or:
> > >
> > > b)
> > >
> > > Define Boolean property atmel,generic-pinconf (perhaps a better name
> > > could be chosen?). If it's not present, parse the node assuming the old
> > > binding. If it is present, parse the node assuming the new binding.
> > Okay.
> >
> > I thought this property string could be generic as it may concern other
> > drivers too
> > (in order to keep compatibility with old dt ABI and add support the
> > generic pinconf binding).
> >
> > Anyway, I prefer the first proposition.
> >
> > pinctrl single driver is already using these names:
> >
> > |compatible = "pinctrl-single" for non generic pinconf binding
> > ||compatible = "pinconf-single" ||for generic pinconf binding|
> >
> > So I think we should use something similar:
> >
> > |compatible = "atmel,at91xx-pinctrl" for non generic pinconf binding
> > ||compatible = "|||atmel,at91xx-|pinconf" ||for generic pinconf binding|
> >
> > What do you think ?
> Hmmm. It is a little odd to switch out the compatible value and invent a
> new binding for the same HW. Isn't it possible to define both sets of
> properties in the binding, and have drivers look for either?

Do you mean something like:

atmel,pins = <xxx>;                /* current dt binding */
atmel,generic-pins = <yyy>;    /* new dt binding */

If that's what you had in mind, it will be a little bit tricky to 
handle, because AFAIK the pinconf_ops
callbacks do not give me any element I could use to deduce the type of 
pinconf (generic or
native).
This implies I have to know early during the probe process which kind of 
binding is in use.

Please tell me if I missed some key points, and this can be easily done.


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