redonkable
/
alistair23-linux
1
0
Fork 0
Code Releases Activity

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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

34
Documentation/i2c/instantiating-devices
View File

@ -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. 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 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 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.) 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 Method 2: Instantiate the devices explicitly
-------------------------------------------- --------------------------------------------