Re: [RFC 4/5] gpiolib: add gpiod_get() and gpiod_put() functions

[Stephen Warren <swarren@wwwdotorg.org>]

On 09/04/2013 05:29 AM, Alexandre Courbot wrote:
> Add gpiod_get() and gpiod_put() functions that provide safer handling of
> GPIOs.
> 
> These functions put the GPIO framework in line with the conventions of
> other frameworks in the kernel, and help ensure every GPIO is declared
> properly and valid while it is used.

> diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h

> +struct gpio_desc *__must_check gpiod_get(struct device *dev,
> +					 const char *con_id);
> +void gpiod_put(struct gpio_desc *desc);

It might be nice to add an "int index" parameter to this function. For
example, a bit-banged parallel bus protocol driver might have 1
chip-select GPIO, 1 clock GPIO, and 8 data GPIOs. gpiod_get(dev, "bus",
0)..gpiod_get(dev, "bus", 7) might be nicer than gpiod_get(dev,
"bus0")..gpiod_get(dev, "bus7")? Possibly for client-simplicity,
implement both gpiod_get(dev, con_id) (as an inline wrapper for ...) and
gpiod_get_index(dev, con_id, index)?

In DT terms, this would map to:

cs-gpios = <&gpio 3 0>;
clock-gpios = <&gpio 5 0>;
bus-gpios = <&gpio 10 0 ... &gpio 17 0>;

... and with the mapping table registration mechanism, we could
presumably add "int index" to struct gpiod_lookup.