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

[André Marques]

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 <mailto: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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