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authorWolfram Sang <wsa@the-dreams.de>2014-02-10 11:03:55 +0100
committerWolfram Sang <wsa@the-dreams.de>2014-02-15 19:46:29 +0100
commitaeca0fe62ac19217cb8158a0c5f6f74e3b8d304b (patch)
tree273a11bf3c94901c8fbc751f14e3893237adad0a /Documentation/i2c
parent79970db213344b4a4034645db5ebfc31571f3fa3 (diff)
downloadlinux-linaro-stable-aeca0fe62ac19217cb8158a0c5f6f74e3b8d304b.tar.gz
Documentation: i2c: describe devicetree method for instantiating devices
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Diffstat (limited to 'Documentation/i2c')
-rw-r--r--Documentation/i2c/instantiating-devices34
1 files changed, 32 insertions, 2 deletions
diff --git a/Documentation/i2c/instantiating-devices b/Documentation/i2c/instantiating-devices
index c70e7a7638d1..6df095a6071e 100644
--- a/Documentation/i2c/instantiating-devices
+++ b/Documentation/i2c/instantiating-devices
@@ -8,8 +8,8 @@ reason, the kernel code must instantiate I2C devices explicitly. There are
several ways to achieve this, depending on the context and requirements.
-Method 1: Declare the I2C devices by bus number
------------------------------------------------
+Method 1a: Declare the I2C devices by bus number
+------------------------------------------------
This method is appropriate when the I2C bus is a system bus as is the case
for many embedded systems. On such systems, each I2C bus has a number
@@ -51,6 +51,36 @@ The devices will be automatically unbound and destroyed when the I2C bus
they sit on goes away (if ever.)
+Method 1b: Declare the I2C devices via devicetree
+-------------------------------------------------
+
+This method has the same implications as method 1a. The declaration of I2C
+devices is here done via devicetree as subnodes of the master controller.
+
+Example:
+
+ i2c1: i2c@400a0000 {
+ /* ... master properties skipped ... */
+ clock-frequency = <100000>;
+
+ flash@50 {
+ compatible = "atmel,24c256";
+ reg = <0x50>;
+ };
+
+ pca9532: gpio@60 {
+ compatible = "nxp,pca9532";
+ gpio-controller;
+ #gpio-cells = <2>;
+ reg = <0x60>;
+ };
+ };
+
+Here, two devices are attached to the bus using a speed of 100kHz. For
+additional properties which might be needed to set up the device, please refer
+to its devicetree documentation in Documentation/devicetree/bindings/.
+
+
Method 2: Instantiate the devices explicitly
--------------------------------------------