1 Raspberry Pi GPIO expander
2
3 The Raspberry Pi 3 GPIO expander is controlled by the VC4 firmware. The
4 firmware exposes a mailbox interface that allows the ARM core to control the
5 GPIO lines on the expander.
6
7 The Raspberry Pi GPIO expander node must be a child node of the Raspberry Pi
8 firmware node.
9
10 Required properties:
11
12 - compatible : Should be "raspberrypi,firmware-gpio"
13 - gpio-controller : Marks the device node as a gpio controller
14 - #gpio-cells : Should be two. The first cell is the pin number, and
15 the second cell is used to specify the gpio polarity:
16 0 = active high
17 1 = active low
18
19 Example:
20
21 firmware: firmware-rpi {
22 compatible = "raspberrypi,bcm2835-firmware";
23 mboxes = <&mailbox>;
24
25 expgpio: gpio {
26 compatible = "raspberrypi,firmware-gpio";
27 gpio-controller;
28 #gpio-cells = <2>;
29 };
30 };
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