[PATCH v3 2/3] dt-bindings: Add pinctrl bindings for mt65xx/mt81xx.

[Linus Walleij]

On Mon, Jan 26, 2015 at 4:57 PM, Sascha Hauer <s.hauer at pengutronix.de> wrote:
> On Tue, Jan 20, 2015 at 10:45:09AM +0100, Linus Walleij wrote:

>> As discussed with Sascha Hauer it is ambigous to use "pins" for
>> a numerical value indicating both a mux setting and a pin. Sascha
>> suggests using "pinmux" and adding this as a secondary generic
>> binding for this type of pin controllers that use numbers and #defines
>> to set up bindings.
>>
>> We should still move these parsing functions to the core.
>
> I tried that for the last few days and failed.
>
> Part of the problem is that the core lacks the data structures to put
> the information in. There is
>
> struct pinctrl_map_mux {
>         const char *group;
>         const char *function;
> };
>
> but its meaning is SoC specific. Some SoCs combine the pins found in a
> dt subnode to one group (i.MX, rockchip, at91) while others make an
> individual group from each single pin (Tegra, others?). Also the
> function string is SoC specific. Some SoCs just define functions like
> "alt1".."altn" which are valid for all groups, others define different
> function names for each group.
>
> Another thing is that the binding gives us numbers, but struct
> pinctrl_map_mux expects strings, so the numbers would have to be
> converted to strings. This is crude since the contents of struct
> pinctrl_map_mux are converted from strings back to numbers later from
> the pinctrl core with the help of the driver. So we would have to
> translate the numbers from the bindings to strings just to convert them
> back to numbers before passing them to the driver later.

So can we use a union?

struct pinctrl_map_mux {
        union group {
              const char *groupstr;
              u16 groupno;
        };
        union function {
              const char *functionstr;
              u16 funcno;
        };
};

The augment the code to reference foo->group.groupstr or
foo->group.groupno etc depending on runpath.

Yours,
Linus Walleij