由于I2C总线驱动为Linux内核自带的总线驱动，在一个新的板子上可能由于不同的定义与芯片原厂定义的I2C管脚有所不同，这时就需要开发人员对设备树信息及内核驱动进行更新。

原理图可知，I2C的SCL对应PF14，SDA对应PF15

在Linux内核中，arch/arm/boot/dts/  设备树文件 --> stm32mp157a-fsmp1a.dts，I2C对应的GPIO复用信息 --> stm32mp15-pinctrl.dtsi。

 驱动程序代码

#include <linux/init.h>       // 包含内核初始化相关的头文件
#include <linux/module.h>     // 包含内核模块相关的头文件
#include <linux/of.h>         // 包含设备树操作相关的头文件
#include <linux/gpio.h>       // 包含 GPIO 操作相关的头文件
#include <linux/of_gpio.h>    // 包含设备树 GPIO 相关的头文件
#include <linux/fs.h>         // 包含文件操作相关的头文件
#include <linux/uaccess.h>    // 包含用户空间访问内核空间相关的头文件
#include <linux/device.h>     // 包含设备相关的头文件
#include <linux/i2c.h>   // 包含 I2C 相关的头文件
#include "i2c_test.h"    // 包含自定义头文件//创建设备号
static int major;
//创建类
static struct class *cls;
//创建设备
static struct device *device;
//创建i2c_client
static struct i2c_client *client;
//保存字符设备数据
static char i2c_buf[100];//获取温湿度数据
int get_hum_tem(int reg)
{int ret = 0;char r_buf  = reg;short value;struct i2c_msg r_msg[] ={[0] = {.addr = client->addr,.flags = 0,.len = 1,.buf = &r_buf,},[1] = {.addr = client->addr,.flags = 1,.len = 2,.buf = (u8 *)&value,},};//发送读取温湿度数据的命令ret = i2c_transfer(client->adapter, r_msg, 2);if(ret != 2){printk("i2c_transfer failed\n");return ret;}return value;
} //end of get_hum_temstatic int led_open(struct inode *inode, struct file *file)
{unsigned int cmajor;//保存次设备号cmajor = iminor(inode);//将次设备号保存到file结构体的private_data中file->private_data = (void *)cmajor;printk("led_open\n");return 0;
}static int led_close(struct inode *inode, struct file *file)
{printk("led_close\n");return 0;
}static int led_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
{unsigned int ret;//从内核空间读取数据到用户空间，如果读取数据的长度大于i2c_buf的长度，按照最大长度读取if(count > sizeof(i2c_buf)){count = sizeof(i2c_buf);}ret = copy_to_user(buf, i2c_buf, count);if(ret < 0){printk("copy_to_user failed\n");return -1;}printk("led_read\n");return 0;
}static int led_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
{unsigned int ret;//将用户空间的数据拷贝到内核空间，如果传输数据的长度大于i2c_buf的长度，按照最大长度传输if (count > sizeof(i2c_buf)){count = sizeof(i2c_buf);}ret = copy_from_user(i2c_buf, buf, count);if (ret < 0){printk("copy_from_user failed\n");return -1;}printk("led_write\n");return 0;
}static long led_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{int hum = 0, tem = 0;//写入用户空间switch(cmd){case GET_HUM:hum = get_hum_tem(0xE5);copy_to_user((int *)arg, &hum, 4);break;case GET_TEM:tem = get_hum_tem(0xE3);copy_to_user((int *)arg, &tem, 4);break;default:break;}printk("led_ioctl\n");return 0;
}//定义file_operations结构体
struct file_operations fops = {.owner = THIS_MODULE,.open = led_open,.release = led_close,.read = led_read,.write = led_write,.unlocked_ioctl = led_ioctl,
};//编写i2c设备驱动
static int myi2c_probe(struct i2c_client *pdev, const struct i2c_device_id *id)
{printk("myi2c_probe\n");client = pdev;//1.创建设备号major = register_chrdev(0, "myi2c", &fops);if (major < 0){printk("register_chrdev failed\n");return -1;}//2.创建类cls = class_create(THIS_MODULE, "myi2c");if (IS_ERR(cls)){printk("class_create failed\n");unregister_chrdev(major, "myi2c");return -1;}//3.创建设备device = device_create(cls, NULL, MKDEV(major, 0), NULL, "myi2c");if (IS_ERR(device)){printk("device_create failed\n");class_destroy(cls);unregister_chrdev(major, "myi2c");return -1;}return 0;
}static int myi2c_remove(struct i2c_client *pdev)
{printk("myi2c_remove\n");    device_destroy(cls, MKDEV(major, 0));class_destroy(cls);unregister_chrdev(major, "myi2c");return 0;
}static const struct of_device_id myplatform_test_match_table[] = {{ .compatible = "johnson,si7006", },{ /* sentinel */ }
};struct i2c_driver myi2c_driver = {.probe = myi2c_probe,.remove = myi2c_remove,.driver = {.name = "myi2c_slave",.of_match_table = myplatform_test_match_table,},
};//一键注册宏定义
module_i2c_driver(myi2c_driver);
MODULE_LICENSE("GPL");

头文件

#ifndef __I2CTEST_H__
#define __I2CTEST_H__#define GET_HUM _IOR('i', 1, int)
#define GET_TEM _IOR('i', 0, int)#endif

应用程序 --> 实现通过I2C获取温湿度数据

#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <arpa/inet.h>
#include "i2c_test.h"int main()
{int hum = 0, tem = 0;float hum1, tem1; // 保存计算完毕后的温湿度数据int fd = 0;//打开设备文件fd = open("/dev/myi2c", O_RDWR);if (fd < 0){printf("open failed\n");return -1;}//读取数据while(1){ioctl(fd, GET_HUM, &hum);ioctl(fd, GET_TEM, &tem);//字节序转换hum = ntohs(hum);tem = ntohs(tem);hum1 = (float)hum * 125 / 65536 - 6;tem1 = tem * 175.72 / 65536 - 46.85;printf("hum = %f, tem = %f\n", hum1, tem1);sleep(1);}   //关闭设备文件close(fd);return 0;
}