[PATCH v2] pinctrl: document semantics vs GPIO

Linus Walleij linus.walleij at linaro.org
Mon Sep 17 04:58:54 EDT 2012

On Fri, Sep 14, 2012 at 7:16 PM, Stephen Warren <swarren at wwwdotorg.org> wrote:
> On 09/14/2012 07:49 AM, Linus Walleij wrote:

>> +If a pin control driver and a GPIO driver is dealing with the same pins
>> +and the use cases involve multiplexing, you MUST implement the pin controller
>> +as a back-end for the GPIO driver like this.
> I might add one caveat to that:
> ==========
> , unless your HW design is such that the GPIO controller can override
> the pin controller's mux state, without the need for any such interaction.
> ==========

OK I buy that, so added this paragraph (slightly rephrased) and pused
for next.

> In the future, I wonder if someone might want the following caveat,
> ==========
> , unless you require that all boards (or device trees) define a system
> hog pinmux configuration that muxes all required GPIO signals as desired.
> ==========
> ... which might be appropriate for HW where GPIO-vs-special-function
> selection is performed in the pinmux controller itself, per-pin. Perhaps
> this is the OMAP special case you mentioned before?

Yeah :-/

I worry about exploding complexity here, so we need to think
about this a bit more...


More information about the linux-arm-kernel mailing list