Basic GPIO API just covering GPIO_DIGITAL_OUTPUT.

{{{#!c
/* a configured GPIO pin handle. this is filled in by rtems_gpio_configure_pin_*
 * and can then be passed to other api functions.
 */
struct struct gpio_pin_handle;

/* fill in gpio_pin struct to use this pin in a digital out manner.
 * must be currently unused.
 * pin_number is a number that is interpreted by the BSP and will be defined
 * with device-specific names such as BBB_P9_33, indicating pin 33 on header P9
 * on the board.
 *
 * the gpio_pin struct is then filled in and can be passed to other functions.
 */
rtems_gpio_configure_pin_digital_out(&gpio_pin_handle, pin_number);

/* for a digital_out pin, set it to logical high */
rtems_gpio_digital_set(&gpio_pin_handle);

/* for a digital_out pin, set it to logical low */
rtems_gpio_digital_clear(&gpio_pin_handle);

/* a currently configured pin is to be released and made unused, allowing repurposing. */
rtems_gpio_release_pin(&gpio_pin_handle);
}}}