[Patch v3 2/2] gpio: Document GPIO hogging mechanism

From: Benoit Parrot
Date: Thu Dec 04 2014 - 16:02:46 EST

Add GPIO hogging documentation to gpio.txt

Signed-off-by: Benoit Parrot <bparrot@xxxxxx>
Changes since v2:
* Updated to the latest hog syntax.

Changes since v1:
* Split the devicetree bindings documentation in its own patch.

Documentation/devicetree/bindings/gpio/gpio.txt | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)

diff --git a/Documentation/devicetree/bindings/gpio/gpio.txt b/Documentation/devicetree/bindings/gpio/gpio.txt
index 3fb8f53..6d88133 100644
--- a/Documentation/devicetree/bindings/gpio/gpio.txt
+++ b/Documentation/devicetree/bindings/gpio/gpio.txt
@@ -103,6 +103,22 @@ 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).
+- direction: A property specifying the direction/value needed. This property
+ can take the folowing values: input, output-high, output-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 +126,13 @@ Example of two SOC GPIO banks defined as gpio-controller nodes:
reg = <0x1400 0x18>;
#gpio-cells = <2>;
+ line_b {
+ gpio-hog;
+ gpios = <6 0>;
+ direction = "output-low";
+ line-name = "foo-bar-gpio";
+ };

qe_pio_e: gpio-controller@1460 {

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