[PATCH V2 1/2] RTEMS GPIO API definition and implementation.

[Ketul Shah]

Hello Andre,

I created a ticket <https://devel.rtems.org/ticket/2390> . Please make the
necessary changes.

Thanks.

Cheers,
Ketul
On 13 August 2015 at 19:38, André Marques <andre.lousa.marques at gmail.com>
wrote:

> On 13-08-2015 14:51, Ketul Shah wrote:
>
> Hi Andre,
>
> Thanks for the reply.
>
> On 13 August 2015 at 19:13, André Marques <andre.lousa.marques at gmail.com>
> wrote:
>
>> Hello Ketul,
>>
>> On 13-08-2015 13:04, Ketul Shah wrote:
>>
>>> Hi Andre,
>>>
>>> Great API and happy to know that it is merged with main line.
>>>
>>> Eventually I implemented GPIO driver for BBB using this API. After
>>> debugging for rtems_gpio_get_value() on BBB I found the following bug.
>>>
>>> For BBB, GPIO pin nos. varies from 0 to 32. So function return type
>>> would be uint32_t instead of uint8_t.
>>>
>>> For BBB I wrote :-
>>>
>>> uint32_t rtems_gpio_bsp_get_value(uint32_t bank, uint32_t pin)
>>> {
>>>   return (mmio_read(bbb_reg(bank, AM335X_GPIO_DATAIN)) & BIT(pin));
>>>
>> So it would be:-  return ((mmio_read(bbb_reg(bank, AM335X_GPIO_DATAIN)) &
> BIT(pin)) > 0);
> Am I correct ?
>
>> }
>>>
>>>
> Yes, but since this function is not used by applications maybe it would be
> best to return the bitmask here and avoid another operation, as
> rtems_gpio_get_value does the mapping to 1 anyway for any value above 0.
>
> So yes the bsp function shall return uint32_t instead of the uint8_t.
> Doxygen also has to be updated.
>
>
>> the rtems_gpio_bsp_get_value returns the value of a GPIO pin, which can
>> only be either 0 or 1. This is not platform dependent. Any value greater
>> than zero should map to 1.
>>
>> I do notice that I forgot this detail in the Pi implementation too, so it
>> is also returning a 32 bit value.
>>
>> The reasoning for the 8-bit return is that the return will always be
>> binary. 0 or non-zero, but by mapping a non-zero value to 1 may make more
>> sense than outputing a 32-bit bitmask, which was the initial approach.
>>
>> Thanks.
>>>
>>> Best Regards,
>>> Ketul
>>>
>>>
>> --André Marques.
>>
>> [snip]
>>
>
>
>
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