0001 Raspberry Pi GPIO expander
0002
0003 The Raspberry Pi 3 GPIO expander is controlled by the VC4 firmware. The
0004 firmware exposes a mailbox interface that allows the ARM core to control the
0005 GPIO lines on the expander.
0006
0007 The Raspberry Pi GPIO expander node must be a child node of the Raspberry Pi
0008 firmware node.
0009
0010 Required properties:
0011
0012 - compatible : Should be "raspberrypi,firmware-gpio"
0013 - gpio-controller : Marks the device node as a gpio controller
0014 - #gpio-cells : Should be two. The first cell is the pin number, and
0015 the second cell is used to specify the gpio polarity:
0016 0 = active high
0017 1 = active low
0018
0019 Example:
0020
0021 firmware: firmware-rpi {
0022 compatible = "raspberrypi,bcm2835-firmware";
0023 mboxes = <&mailbox>;
0024
0025 expgpio: gpio {
0026 compatible = "raspberrypi,firmware-gpio";
0027 gpio-controller;
0028 #gpio-cells = <2>;
0029 };
0030 };
