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Documentation: i2c: describe devicetree method for instantiating devices 

Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
hifive-unleashed-5.1
Wolfram Sang 2014-02-10 11:03:55 +01:00
parent 79970db213
commit aeca0fe62a
1 changed files with 32 additions and 2 deletions
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34
Documentation/i2c/instantiating-devices
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@ -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
--------------------------------------------