| Raspberry Pi GPIO expander |
| |
| The Raspberry Pi 3 GPIO expander is controlled by the VC4 firmware. The |
| firmware exposes a mailbox interface that allows the ARM core to control the |
| GPIO lines on the expander. |
| |
| The Raspberry Pi GPIO expander node must be a child node of the Raspberry Pi |
| firmware node. |
| |
| Required properties: |
| |
| - compatible : Should be "raspberrypi,firmware-gpio" |
| - gpio-controller : Marks the device node as a gpio controller |
| - #gpio-cells : Should be two. The first cell is the pin number, and |
| the second cell is used to specify the gpio polarity: |
| 0 = active high |
| 1 = active low |
| |
| Example: |
| |
| firmware: firmware-rpi { |
| compatible = "raspberrypi,bcm2835-firmware"; |
| mboxes = <&mailbox>; |
| |
| expgpio: gpio { |
| compatible = "raspberrypi,firmware-gpio"; |
| gpio-controller; |
| #gpio-cells = <2>; |
| }; |
| }; |
