* @return 0 if ok, -1 on error
*/
int gpio_request(unsigned gpio, const char *label);
* @return 0 if ok, -1 on error
*/
int gpio_request(unsigned gpio, const char *label);
* @return 0 if ok, -1 on error
*/
int gpio_set_value(unsigned gpio, int value);
* @return 0 if ok, -1 on error
*/
int gpio_set_value(unsigned gpio, int value);