linux i2c bus bus read and write

The i2cs device does not need to write a separate driver, and can directly operate the i2c bus in the application for reading and writing.

#include <sys/types.h>
#include <string.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <termios.h>
#include <stdio.h>
#include <unistd.h> //open close
#include <sys/ioctl.h>
#include <linux/types.h> 
#include <linux/i2c-dev.h>
#include <linux/i2c.h>
#include <errno.h>
#include <stdint.h>


#define I2C_DEV "/dev/i2c-0" 
#define CHIP_ADDR 0x30 


int i2c_read(void)
{
    
    
    int ret=0;
    struct i2c_rdwr_ioctl_data data;
    
	char buf[256]={
    
    0};
	
    // 1.打开设备
    int fd= open(I2C_DEV, O_RDWR);
    if(fd < 0){
    
    
        printf("err.open i2c fail.%s", strerror(errno));
        return -1;
    }

    data.msgs = (struct i2c_msg *)malloc(2*sizeof(struct i2c_msg)); 
	
	//2.写入reg,读取数据
    data.nmsgs = 2;         		//消息的数目
    data.msgs[0].len = 1;			//写入1byte
    data.msgs[0].addr = CHIP_ADDR;  //从设备地址
    data.msgs[0].flags = 0;     	//flags-0:写 1:读.
    data.msgs[0].buf = buf;
	data.msgs[0].buf[0] = 0x12;		//reg
	
    data.msgs[1].len = 32;			//读取32bytes
    data.msgs[1].addr = CHIP_ADDR; 	//从设备地址
    data.msgs[1].flags = I2C_M_RD;  //flags-0:写 1:读.
    data.msgs[1].buf = (unsigned char *)malloc(32);
    memset(data.msgs[1].buf,0,32);

    //3.使用ioctl写入&读取数据
    ret = ioctl(fd,I2C_RDWR,(unsigned long)&data);
    if (ret < 0) {
    
    
        printf("ioctl: %s\n", strerror(errno));
        goto __err;
    }

	printf("read:%s\n",data.msgs[1].buf);
	
__err:
    free(data.msgs[1].buf);
    free(data.msgs);
    //4.关闭设备
    close(fd); 
    return ret;
}

int i2c_write(void)
{
    
    
    int ret=0;
    struct i2c_rdwr_ioctl_data data;
    
    // 1.打开设备
    int fd= open(I2C_DEV, O_RDWR);
    if(fd< 0){
    
    
        printf("err\n");
        return -1;
    }
    
    data.msgs = (struct i2c_msg *)malloc(sizeof(struct i2c_msg)); 

    // 2.读取数据
    data.nmsgs = 1;
    data.msgs[0].len = 32;
    data.msgs[0].addr = CHIP_ADDR; 	//从设备地址
    data.msgs[0].flags = I2C_M_RD;  //flags-0:写 1:读.
    data.msgs[0].buf = (unsigned char *)malloc(32);

	// 3.使用ioctl读数据
	ret = ioctl(fd,I2C_RDWR,(unsigned long)&data);
	if (ret < 0) {
    
    
		printf("ioctl: %s\n", strerror(errno));
		break;
	}

	printf("read:%s\n",data.msgs[0].buf);

    free(data.msgs[0].buf);
    free(data.msgs);
    //4.关闭设备
    close(fd); 
    return ret;
}