如何在Linux中访问IIO设备驱动程序

Question

I a noob to Linux device drivers.

I have an IIO driver with me (for OPT3001 ambient light sensor) , operating over the I2C bus, which has been compiled successfully in the kernel (version 3.18). The device tree is modified to match the compatible field, present in the driver.

The problem is how do I access this driver to get some data in the userspace ?

The driver has some callbacks for read and write registered in a structure. Should I call them directly in my C file ?

Answer 1

You can use the userspace API provided by:

#include <linux/i2c-dev.h>

Using it you can open de bus /dev/i2c-X (X=0,1,2,...), set device address using ioctl call, and use read and write operations to read and write to/from the bus.

Also, you can install "i2c-tools" package (apt-get install i2c-tools), to install userspace tools like i2cset, i2cget and i2cdetect, very useful for testing the I2C bus and the device connected to it.

Answer 2

you have differents possibilities :

• your driver provide a /dev node you can open in you C file.
• your driver provide informations through sysfs.

in case of a /dev node, you can have access to file operations (open, read, write, ioctl). you just have to open your file 1 time and each read() call will read the value from the sensor.

in case of sysfs, you should find the file to open/read in /sys/class/...