linux-kernel - [Patch v5 2/2] gpio: Document GPIO hogging mechanism

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Date:	Fri, 19 Dec 2014 14:07:51 -0600
From:	Benoit Parrot <bparrot@...com>
To:	Linus Walleij <linus.walleij@...aro.org>
CC:	<linux-gpio@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<devicetree@...r.kernel.org>, Alexandre Courbot <gnurou@...il.com>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Jiri Prchal <jiri.prchal@...ignal.cz>,
	Pantelis Antoniou <panto@...oniou-consulting.com>,
	Benoit Parrot <bparrot@...com>
Subject: [Patch v5 2/2] gpio: Document GPIO hogging mechanism

Add GPIO hogging documentation to gpio.txt

Signed-off-by: Benoit Parrot <bparrot@...com>
Reviewed-by: Alexandre Courbot <acourbot@...dia.com>
---
 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 b9bd1d6..f5d2717 100644
--- a/Documentation/devicetree/bindings/gpio/gpio.txt
+++ b/Documentation/devicetree/bindings/gpio/gpio.txt
@@ -115,6 +115,22 @@ 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).
+- state:     A property specifying the direction/value needed. This property
+	     can take the following 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@...0 {
@@ -122,6 +138,13 @@ 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>;
+			state = "output-low";
+			line-name = "foo-bar-gpio";
+		};
 	};
 
 	qe_pio_e: gpio-controller@...0 {
-- 
1.8.5.1

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