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SubjectRe: [RFC 4/5] gpiolib: add gpiod_get() and gpiod_put() functions
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On Wed, Sep 4, 2013 at 9:56 PM, Stephen Warren <swarren@wwwdotorg.org> wrote:
> 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.

This is an interesting usability aspect of the API, so I'd especially
like some input from the ACPI people on this as well.

Paging Mika, Rafael, Mathias.

Yours,
Linus Walleij


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