[PATCH 2/7] pinctrl: pinconf-generic: Infer map type from DT property

On Tue, 2014-11-11 at 01:29PM +0100, Linus Walleij wrote:

On Wed, Nov 5, 2014 at 2:56 PM, Laurent Pinchart
[off-list ref] wrote:

quoted

On Monday 03 November 2014 11:05:26 Soren Brinkmann wrote:

quoted

With the new 'groups' property, the DT parser can infer the map type
from the fact whether 'pins' or 'groups' is used to specify the pin
group to work on.
To maintain backwards compatibitliy with current usage of the DT
binding, this is only done when an invalid map type is passed to the
parsing function.

The Renesas PFC implements similar bindings with using the vendor-specific
properties "renesas,pins" and "renesas,groups" (bindings and implementation
available at Documentation/devicetree/bindings/pinctrl/renesas,pfc-pinctrl.txt
and drivers/pinctrl/sh-pfc/pinctrl.c respectively).

The Renesas implementation is a bit more generic in that it allows both pins
and groups to be specified in a single subnode. Do you think that feature
would make sense for pinconf-generic as well ?

I think for generic pin controllers either nodes with:

{
    function = "foo";
    pins = "A0", "A1", "A2";
}

or

{
    function = "foo";
    groups = "bar", "baz";
}

In parsing this it's easy to just look for "function" then see if
we're mapping to groups or pins.

It'd be nice if we could then centralize parsing of functions/pins/groups
and add the non-renesas-prefixed configs as alternatives to genericized
the bindings, while keeping backward compatibility.

I think the generic parser can't handle that currently. When it finds
'function' it passes the PINs to pinctrl_utils_add_map_mux(). That
function fails when it doesn't receive a group.
I don't know if the non-generic pinctrl drivers solve that somehow, but
pinconf-generic can't handle pins + function in the same node if we
change the meaning of pins to actually just be pins.

That is why I chose the "kludgy" approach. To maintain current behavior.
If nobody needs that though, things could change I guess.

	S?ren