Add GPIO hogging documentation to gpio.txt
Signed-off-by: Benoit Parrot <bparrot@xxxxxx>
Reviewed-by: Alexandre Courbot <acourbot@xxxxxxxxxx>
---
Documentation/devicetree/bindings/gpio/gpio.txt | 30 +++++++++++++++++++++++++
1 file changed, 30 insertions(+)
diff --git a/Documentation/devicetree/bindings/gpio/gpio.txt b/Documentation/devicetree/bindings/gpio/gpio.txt
index b9bd1d6..a0ce2bd 100644
--- a/Documentation/devicetree/bindings/gpio/gpio.txt
+++ b/Documentation/devicetree/bindings/gpio/gpio.txt
@@ -115,6 +115,29 @@ Every GPIO controller node must contain both an empty "gpio-controller"
property, and a #gpio-cells integer property, which indicates the number of
cells in a gpio-specifier.
+The GPIO chip may contain GPIO hog definitions. GPIO hogging is a mechanism
+providing automatic GPIO request and configuration as part of the
+gpio-controller's driver probe function.
+
+Each GPIO hog definition is represented as a child node of the GPIO controller.
+Required properties:
+- gpio-hog: A property specifying that this child node represent a GPIO hog.
+- gpios: Store the GPIO information (id, flags, ...). Shall contain the
+ number of cells specified in its parent node (GPIO controller
+ node).
+Only one of the following properties scanned in the order shown below.
+This means that when multiple properties are present they will be searched
+in the order presented below and the first match is taken as the intended
+configuration.
+- input: A property specifying to set the GPIO direction as input.
+- output-low A property specifying to set the GPIO direction as output with
+ the value low.
+- output-high A property specifying to set the GPIO direction as output with
+ the value high.
+
+Optional properties:
+- line-name: The GPIO label name. If not present the node name is used.
+
Example of two SOC GPIO banks defined as gpio-controller nodes:
qe_pio_a: gpio-controller@1400 {
@@ -122,6 +145,13 @@ Example of two SOC GPIO banks defined as gpio-controller nodes:
reg = <0x1400 0x18>;
gpio-controller;
#gpio-cells = <2>;
+
+ line_b {
+ gpio-hog;
+ gpios = <6 0>;
+ output-low;
+ line-name = "foo-bar-gpio";
+ };
};
qe_pio_e: gpio-controller@1460 {
--
1.8.5.1
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