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Commit aeca0fe6 authored by Wolfram Sang's avatar Wolfram Sang
Browse files

Documentation: i2c: describe devicetree method for instantiating devices 



Signed-off-by: default avatarWolfram Sang <wsa@the-dreams.de>
parent 79970db2

Documentation/i2c/instantiating-devices

+32 −2
Original line number Diff line number Diff line
@@ -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

--------------------------------------------