int gpio_is_valid(int number);

/* set as input or output, returning 0 or negative errno */
int gpio_direction_input(unsigned gpio);
int gpio_direction_output(unsigned gpio, int value);

/* GPIO INPUT: return zero or nonzero */
int gpio_get_value(unsigned gpio);

/* GPIO OUTPUT */
void gpio_set_value(unsigned gpio, int value);

int gpio_cansleep(unsigned gpio);

/* GPIO INPUT: return zero or nonzero, might sleep */
int gpio_get_value_cansleep(unsigned gpio);

/* GPIO OUTPUT, might sleep */
void gpio_set_value_cansleep(unsigned gpio, int value);

/* request GPIO, returning 0 or negative errno.
* non-null labels may be useful for diagnostics.
*/
int gpio_request(unsigned gpio, const char *label);

/* release previously-claimed GPIO */
void gpio_free(unsigned gpio);

/* map GPIO numbers to IRQ numbers */
int gpio_to_irq(unsigned gpio);

/* map IRQ numbers to GPIO numbers (avoid using this) */
int irq_to_gpio(unsigned irq);

if (!sw->both_edges) {
 if (gpio_get_value(sw->gpio)) {
 set_irq_type(gpio_to_irq(sw->gpio), IRQ_TYPE_EDGE_FALLING);
 } else {
 set_irq_type(gpio_to_irq(sw->gpio), IRQ_TYPE_EDGE_RISING);
 }
}