[Patch v2 2/2] gpio: Document GPIO hogging mechanism

Benoit Parrot
2014-11-20T23:54:59Z

Add GPIO hogging documentation to gpio.txt

Signed-off-by: Benoit Parrot <bparrot@ti.com>
---
Changes since v1:
* Split the devicetree bindings documentation in its own patch.

Documentation/devicetree/bindings/gpio/gpio.txt | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)

diff --git a/Documentation/devicetree/bindings/gpio/gpio.txt b/Documentation/devicetree/bindings/gpio/gpio.txt
index 3fb8f53..82755e2 100644
--- a/Documentation/devicetree/bindings/gpio/gpio.txt
+++ b/Documentation/devicetree/bindings/gpio/gpio.txt
@@ -103,6 +103,24 @@ 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).
+- input: a property specifying to set the GPIO direction as input.
+- output-high: a property specifying to set the GPIO direction to output with
+ the value high.
+- output-low: a property specifying to set the GPIO direction to output with
+ the value low.
+
+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 {
@@ -110,6 +128,13 @@ Example of two SOC GPIO banks defined as gpio-controller nodes:
reg = <0x1400 0x18>;
gpio-controller;
#gpio-cells = <2>;
+
+ line_b: line_b {
+ gpio-hog;
+ gpios = <6 0>;
+ output-low;
+ line-name = "foo-bar-gpio";
+ };
};

qe_pio_e: gpio-controller@1460 {
--
1.8.5.1