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- 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>;
- };
- };
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