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SubjectRe: [RFC 5/5] gpiolib: update documentation
On Wed, Sep 4, 2013 at 1:29 PM, Alexandre Courbot <> wrote:

> +The GPIO framework has quite a bit of history behind it. Currently there exist
> +two different (although very similar) ways of using GPIOs:
> +
> + - The legacy integer-based interface represents GPIOs as integers. This is
> + the "historic" way of accessing GPIOs and it was done so because it makes
> + GPIOs easy to represent and also allows for the compiler to statically know
> + the GPIO number and use fast-paths on GPIOs for which performance matters.
> + However, GPIOs can easily be forged this way, and the maximum number of
> + GPIOs in the system must be known in advance. Functions of this interface
> + are prefixed with "gpio_".
> +
> + - The new descriptor-based interface represents GPIOs as an opaque pointer.
> + This ensures GPIOs are properly acquired before usage, and also does not
> + presume anything about their underlying implementation. This interface
> + provides get/put functions to acquire GPIOs according to their function for
> + a particular device, similarly to e.g. the regulator framework. For these
> + reasons, it is the preferred way to access GPIOs. Its functions are prefixed
> + with "gpiod_".

I would put all the new style gpiod_* based things on top of the file, and
all the old stuff under a separate heading below DEPRECATED LEGACY INTERFACE
so it's crystal clear that this is going away.

Linus Walleij

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