安卓平台用户空间bin工具读写I2C

        在linux内核中调试I2C设备，除了打印uart log来查看I2C的寄存器值之外（也可以通过驱动的proc，sysfs等调试），还可以通过在用户空间执行bin文件查看寄存器值，且还可写入寄存器值。参考文章http://blog.youkuaiyun.com/21cnbao/article/details/7919055。原理是通过/dev/i2c-n节点，用户可以在userspace直接访问板上的i2c外设寄存器，主要是透过I2C_RDWR这个IO控制命令将i2c_msg数组传递给kernel去执行。

主文件i2c-util.c

#include <stdio.h>  
#include <linux/types.h>  
#include <fcntl.h>  
#include <unistd.h>  
#include <stdlib.h>  
#include <sys/types.h>  
#include <sys/ioctl.h>  
#include <errno.h>  
#include <assert.h>  
#include <string.h>  
#include <linux/i2c.h>  

/* This is the structure as used in the I2C_RDWR ioctl call */  
struct i2c_rdwr_ioctl_data {  
        struct i2c_msg __user *msgs;    /* pointers to i2c_msgs */  
        __u32 nmsgs;                    /* number of i2c_msgs */  
};  
  
int i2c_read_reg(char *dev, unsigned char *buf, unsigned slave_address, unsigned reg_address, int len)  
{  
    struct i2c_rdwr_ioctl_data work_queue;  
    unsigned char w_val = reg_address;  
    int ret;  
  
    int fd = open(dev, O_RDWR);  
    if (!fd) {  
        printf("Error on opening the device file\n");  
        return 0;  
    }  
  
    work_queue.nmsgs = 2;  
    work_queue.msgs = (struct i2c_msg*)malloc(work_queue.nmsgs *sizeof(struct  
            i2c_msg));  
    if (!work_queue.msgs) {  
        printf("Memory alloc error\n");  
        close(fd);  
        return 0;  
    }  
  
    ioctl(fd, I2C_TIMEOUT, 2);  
    ioctl(fd, I2C_RETRIES, 1);  
  
    (work_queue.msgs[0]).len = 1;  
    (work_queue.msgs[0]).addr = slave_address;  
    (work_queue.msgs[0]).buf = &w_val;  
  
    (work_queue.msgs[1]).len = len;  
    (work_queue.msgs[1]).flags = I2C_M_RD;  
    (work_queue.msgs[1]).addr = slave_address;  
    (work_queue.msgs[1]).buf = buf;  
  
    ret = ioctl(fd, I2C_RDWR, (unsigned long) &work_queue);  
    if (ret < 0) {  
        printf("Error during I2C_RDWR ioctl with error code: %d\n", ret);  
        close(fd);  
        free(work_queue.msgs);  
        return 0;  
    } else {  
        printf("read salve:%02x reg:%02x\n", slave_address, reg_address);  
        close(fd);  
        free(work_queue.msgs);  
        return len;  
    }  
}  
  
int i2c_write_reg(char *dev, unsigned char *buf, unsigned slave_address, unsigned reg_address, int len)  
{  
    struct i2c_rdwr_ioctl_data work_queue;  
    unsigned char w_val = reg_address;  
    unsigned char w_buf[len+1];  
    int ret;  
  
    w_buf[0] = reg_address;  
  
    int fd = open(dev, O_RDWR);  
    if (!fd) {  
        printf("Error on opening the device file\n");  
        return 0;  
    }  
  
    work_queue.nmsgs = 1;  
    work_queue.msgs = (struct i2c_msg*)malloc(work_queue.nmsgs *sizeof(struct  
            i2c_msg));  
    if (!work_queue.msgs) {  
        printf("Memory alloc error\n");  
        close(fd);  
        return 0;  
    }  
  
    ioctl(fd, I2C_TIMEOUT, 2);  
    ioctl(fd, I2C_RETRIES, 1);  
  
    (work_queue.msgs[0]).len = 1 + len;  
    (work_queue.msgs[0]).addr = slave_address;  
    (work_queue.msgs[0]).buf = w_buf;  
  
    memcpy(w_buf + 1, buf, len);  
  
    ret = ioctl(fd, I2C_RDWR, (unsigned long) &work_queue);  
    if (ret < 0) {  
        printf("Error during I2C_RDWR ioctl with error code: %d\n", ret);  
        close(fd);  
        free(work_queue.msgs);  
        return 0;  
    } else {  
        printf("write salve:%02x reg:%02x\n", slave_address, reg_address);  
        close(fd);  
        free(work_queue.msgs);  
        return len;  
    }  
}  
  
int main(int argc, char **argv)  
{  
    unsigned int fd;  
    unsigned int slave_address, reg_address;  
    unsigned r_w;  
    unsigned w_val;  
    unsigned char rw_val;  
  
    if (argc < 5) {  
        printf("Usage:\n%s /dev/i2c-x start_addr reg_addr rw[0|1] [write_val]\n", argv[0]);  
        return 0;  
    }  
  
    fd = open(argv[1], O_RDWR);  
  
    if (!fd) {  
        printf("Error on opening the device file %s\n", argv[1]);  
        return 0;  
    }  
  
    sscanf(argv[2], "%x", &slave_address);  
    sscanf(argv[3], "%x", &reg_address);  
    sscanf(argv[4], "%d", &r_w);  
  
    if (r_w == 0) {  
        i2c_read_reg(argv[1], &rw_val, slave_address, reg_address, 1);  
        printf("Read %s-%x reg %x, read value:%x\n", argv[1], slave_address, reg_address, rw_val);  
    } else {  
        if (argc < 6) {  
            printf("Usage:\n%s /dev/i2c-x start_addr reg_addr r|w[0|1] [write_val]\n", argv[0]);  
            return 0;  
        }  
        sscanf(argv[5], "%d", &w_val);  
        if ((w_val & ~0xff) != 0)  
            printf("Error on written value %s\n", argv[5]);  
  
        rw_val = (unsigned char)w_val;  
        i2c_write_reg(argv[1], &rw_val, slave_address, reg_address, 1);  
    }  
  
    return 0;  
}  

Android.mk如下：

 

 

LOCAL_PATH:= $(call my-dir)

include $(CLEAR_VARS)
#LOCAL_FORCE_STATIC_EXECUTABLE := true

LOCAL_SRC_FILES:= \
    i2c-util.c

LOCAL_C_INCLUDES += bionic \
$(call include-path-for, libhardware_legacy)/hardware_legacy

LOCAL_MODULE:=i2c-util

LOCAL_MODULE_TAGS := optional

LOCAL_STATIC_LIBRARIES := libfs_mgr libcutils libc

LOCAL_SHARED_LIBRARIES := libhardware_legacy libnetutils liblog

include $(BUILD_EXECUTABLE)

将这两个文件放置在external\i2c-util\下，通过mmm编译在system\bin\下生成i2c-util。使用方法：假设TP挂在i2c0上，TPi2c地址0x10，读寄存器地址3的数据。0读1写

写方法，往3地址写入数据4。验证方法把写进去的值读出来看看对不对，即可。

关于I2C驱动的详解，参见：https://www.cnblogs.com/yihujiu/p/6390466.html。里面有讲述i2c_dev和i2c_drv的注册方式，通常情况下用在一个文件中完成。