The Raspberry Pi 3 GPIO expander is controlled by the VC4 firmware over
I2C. The firmware mailbox interface allows the ARM core to control the
GPIO lines.
Signed-off-by: Baruch Siach <baruch@xxxxxxxxxx>
---
.../bindings/gpio/brcm,bcm2835-expgpio.txt | 24 ++++++++++++++++++++++
1 file changed, 24 insertions(+)
create mode 100644 Documentation/devicetree/bindings/gpio/brcm,bcm2835-expgpio.txt
diff --git a/Documentation/devicetree/bindings/gpio/brcm,bcm2835-expgpio.txt b/Documentation/devicetree/bindings/gpio/brcm,bcm2835-expgpio.txt
new file mode 100644
index 000000000000..55257f31a9be
--- /dev/null
+++ b/Documentation/devicetree/bindings/gpio/brcm,bcm2835-expgpio.txt
@@ -0,0 +1,24 @@
+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.
+
+Required properties:
+
+- compatible : Should be "brcm,bcm2835-expgpio"
+- 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
+- firmware : Reference to the RPi firmware device node
+
+Example:
+
+expgpio: expgpio {
+ compatible = "brcm,bcm2835-expgpio";
+ gpio-controller;
+ #gpio-cells = <2>;
+ firmware = <&firmware>;
+};
--
2.15.1
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