[PATCH] pio: add arch specific gpio_is_valid() function

[David Brownell]

> gpio_is_valid determines whether a gpio /can/ be attached to acontroller,

Or more simply:  whether its numeric prameter is
a valid argument to gpio_request() and friends.


 gpio_request determines whether that gpio
> currently /is/
> attached to a controller.

Of course, "controller" is out of sight of folk
just using GPIOs.  Otherwise, that's a fair take
on one set of gpio_request() error reports.


  Part of the confusion seems
> to come at least
> in part from the overlooking of facility for dynamically added gpio numbers.

Maybe, but I think most of it came from folk who
expected "valid" to mean (your terminology) the
GPIO number is now connected to a controller.
(Otherwise $SUBJECT would be meaningless since
there'd be no arch-specific issue.
> 
> Fix the documentation to clarify these points.

Patch is forthcoming.