[Linux驱动炼成记] 01-用户空间操作IIC

/* 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 */
};

struct i2c_msg {
	__u16 addr;	/* slave address			*/
	__u16 flags;
#define I2C_M_TEN		0x0010	/* this is a ten bit chip address */
#define I2C_M_RD		0x0001	/* read data, from slave to master */
#define I2C_M_NOSTART		0x4000	/* if I2C_FUNC_PROTOCOL_MANGLING */
#define I2C_M_REV_DIR_ADDR	0x2000	/* if I2C_FUNC_PROTOCOL_MANGLING */
#define I2C_M_IGNORE_NAK	0x1000	/* if I2C_FUNC_PROTOCOL_MANGLING */
#define I2C_M_NO_RD_ACK		0x0800	/* if I2C_FUNC_PROTOCOL_MANGLING */
#define I2C_M_RECV_LEN		0x0400	/* length will be first received byte */
	__u16 len;		/* msg length				*/
	__u8 *buf;		/* pointer to msg data			*/
};

int i2cWriteByte(int* i2c, int devAddr, int slaveAddr, int len, unsigned char data_buf[])
{
    int ret = 0;
    struct i2c_rdwr_ioctl_data ctl_data;
    struct i2c_msg msg;
    unsigned char msg_buf[50];
    memset((void *) msg_buf, 0, 50);
    msg_buf[0] = (unsigned char) (slaveAddr & 0x00ff); //第0位存放寄存器地址
    if (data_buf == NULL) {
        return -1;
    }

    if (len < 50) {
        memcpy((void *) &msg_buf[1], data_buf, len);  //第1位之后是数据
    } else {
        printf("i2c write error!\n");
        return -1;
    }
    msg.addr = devAddr;  //从设备地址
    msg.flags = I2C_M_WR;
    msg.len = 1 + len;
    msg.buf = msg_buf;
    ctl_data.nmsgs = 1;
    ctl_data.msgs = &msg;
    ret = ioctl(*i2c, I2C_RDWR, &ctl_data);
    usleep(5 * 1000);
    return ret;
}