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