[GSOC] rtems GPIO API

[Alan Cudmore]

Hi Andre,
Please see my comments below:
Alan

On 5/22/2014 6:30 PM, Andre Marques wrote:
> Hello,
>
> I will start my GSOC project with a GPIO driver for the RPi BSP, and 
> part of the GPIO driver code will not be specific to the RPi but to 
> any board with a GPIO interface. With code reuse in mind and since I 
> did not found any "generic" API for the GPIO interface in the RTEMS 
> code base, I intend to propose here an initial *rough* draft of what 
> this API may look like.
>

Do you think a gpio API has advantages over Pierre's driver/ioctl based 
driver?
https://github.com/pficheux/raspberry_pi/blob/master/RTEMS/gpio_driver

Feedback from others would be welcome. Pierre offered this as a generic 
GPIO driver interface for RTEMS earlier, but did not get much feedback.

> To initialize the API:
>
> rtems_gpio_initialize (struct gpio_config)
>
> which would initialize the API with a specific GPIO peripheral 
> configuration: number of gpio pins, gpio register addresses, ...
>
> To set a gpio pin as input or output (the direction would be a macro):
>
> rtems_gpio_direction (int gpio, int direction)

Does the gpio serve as the GPIO pin number in this API?

>
> To set a gpio pull resistor (either pull up/down or no pull resistor):
>
> rtems_gpio_set_Pull (int gpio, int pull)
>
Maybe use lower case 'p' for this api to be consistent.

> Some GPIO I/O:
>
> rtems_gpio_set(int gpio)
> rtems_gpio_clr (int gpio)
> rtems_gpio_read_value (int gpio)

Use  rtems_gpio_get instead of read_value?

>
> And interrupt management:
>
> rtems_int_enable (int gpio, rtems_interrupt_level int)
> rtems_int_disable (int gpio)
> rtems_int_clear (int gpio)

Do you mean to have rtems_gpio_int_xxx  ?

>
> Would appreciate some feedback on this.
>
> --Andre Marques.
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