As with all bus dev DRV models, when we get a module, all we need to do is dev? DRV, the device driver

1, device
Method 1. Write an i2c_device.c yourself

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/i2c.h>
#include <linux/err.h>
#include <linux/regmap.h>
#include <linux/slab.h>
 
//0x50 indicates the address of I2C device, which can be found in the I2C device chip manual
static struct i2c_board_info at24cxx_info = {	
	I2C_BOARD_INFO("at24c08", 0x50),//This name should be the same as the name in the ID table of the drv program
};
 
static struct i2c_client *at24cxx_client;
 
static int at24cxx_dev_init(void)
{
	struct i2c_adapter *i2c_adap;
 
	i2c_adap = i2c_get_adapter(0);//The EEPROM to be tested here is connected to I2C bus 0, so the parameter here is 0
	at24cxx_client = i2c_new_device(i2c_adap, &at24cxx_info);
	i2c_put_adapter(i2c_adap);
	
	return 0;
}
 
static void at24cxx_dev_exit(void)
{
	i2c_unregister_device(at24cxx_client);
}
 
module_init(at24cxx_dev_init);
module_exit(at24cxx_dev_exit);
MODULE_LICENSE("GPL");

Method 2. Add device information directly to board level files
(1) Find the corresponding mach file in the directory of and arch/arm / to register
arch\arm\mach-s3c2440/mach-mini2440.c

static struct i2c_board_info i2c_devs[] __initdata = {
	{ I2C_BOARD_INFO("eeprom", 0x50), },
   { 
        I2C_BOARD_INFO("isp1301_omap", 0x2d), 
        .irq        = OMAP_GPIO_IRQ(125), 
    }, 
};

After adding the concept of device tree to Linux kernel, we will understand it more clearly with device tree

(2) Device tree for registration (my method)

    &i2c1 { 
        pinctrl-names = "default"; 
        pinctrl-0 = <&i2c1_pins>;
        status = "okay";
        clock-frequency = <400000>;

        tca9555: tca9555@20 {
            compatible = "ti,tca9555";
            reg = <0x20>;
    };

Two, driver
Driver is the so-called driver we usually get from module manufacturers. How to implement driver?

Refer to the following post
I2C device driver under Linux 3.5
New handwritten Linux I2C driver