* /dev/gpioa minor 0, 8 bit GPIO, each bit can change direction
* /dev/gpiob minor 1, 18 bit GPIO, each bit can change direction
* /dev/gpioc minor 2, 18 bit GPIO, each bit can change direction
* /dev/gpioa minor 0, 8 bit GPIO, each bit can change direction
* /dev/gpiob minor 1, 18 bit GPIO, each bit can change direction
* /dev/gpioc minor 2, 18 bit GPIO, each bit can change direction