驱动中的IIC设备添加

现在很多外设都会用到IIC来进行通讯，记录iic写驱动的写法，以g-sensor操作为例

首先需要将IIC操作的设备挂载的IIC总线上去，有两种写法

1.在arch/arm/mach-s5pv210/mach-x210.c中添加设备到相应的IIC总线上,示例如下

static struct i2c_board_info  s5k4ba_i2c_info = {
     I2C_BOARD_INFO("S5K4BA", 0x2d),                                                                                                             
     .platform_data = &s5k4ba_plat,
}; 

/* I2C2 */
 static struct i2c_board_info i2c_devs2[] __initdata = {
     {
 #if defined(CONFIG_SMDKC110_REV03) || defined(CONFIG_SMDKV210_REV02)
         /* The address is 0xCC used since SRAD = 0 */
         I2C_BOARD_INFO("max8998", (0xCC >> 1)),
         .platform_data = &max8998_pdata,
 #else
         /* The address is 0xCC used since SRAD = 0 */
         I2C_BOARD_INFO("max8698", (0xCC >> 1)),
         .platform_data = &max8698_pdata,
 #endif
     },
 };  

这样在IIC总线初始化过程中就会为我们的iic设备分配相应的client结构体并自动注册，我们只需要实现我们的驱动程序即可。

2.直接在驱动里面来添加我们的iIC设备，虽然这不是正规的设备和驱动分离思想，但是还是应该知道如何去在驱动中添加IIC设备，这样能看懂其他不是正规做法的代码。
在驱动程序中添加IIC设备如下代码示例：

static int KXTF9_i2c_register(void)
{
    struct i2c_board_info info;
    struct i2c_adapter *adapter; 		  	 //adapter  即iic总线
    struct i2c_client *client;     	 		  //client 即iIC设备
   
   //分配设置一个 i2c_board_info  
    memset(&info, 0, sizeof(struct i2c_board_info));
    info.addr = KXTF9_I2C_ADDRESS;
    strlcpy(info.type, "s3c-Gsensor-kxtf9", I2C_NAME_SIZE); //I2C_NAME_SIZE 20

    adapter = i2c_get_adapter(I2C_BUS);  					  //I2C_BUS 0 获得IIC0 总线adapter
    if (!adapter) 
    {
        sensor_dbg(KERN_ERR "can't get i2c adapter 0 for s3c-Gsensor-kxtf9\n");
        return -ENODEV;
    }

    client = i2c_new_device(adapter, &info);   			//在iIC0 总线上添加刚才构造的i2c_board_info 得到一个client
    i2c_put_adapter(adapter);
    if (!client) 
    {
        sensor_dbg(KERN_ERR "can't add i2c device at 0x%x\n", (unsigned int)info.addr);
        return -ENODEV;
    }

    sensor_i2c_client = client;

    return 0;
}

在驱动注册中匹配到设备相应的probe函数会被执行

static const struct i2c_device_id sensor_i2c_id[] = {
    { "s3c-Gsensor-kxtf9", 0, },
    { }
};
static struct i2c_driver sensor_i2c_driver = {
	.driver = {
		.name	= "s3c-Gsensor-kxtf9",   
       	.owner  = THIS_MODULE,
	},
	.probe		= sensor_i2c_probe,
	.remove		= sensor_i2c_remove,
	//.suspend	= sensor_i2c_suspend,
	//.resume		= sensor_i2c_resume,
	.id_table	= sensor_i2c_id,  			 //driver  name匹配上面的i2c_board_info   里面的type名称 执行probe函数
};

static int sensor_i2c_probe(struct i2c_client *client, const struct i2c_device_id *id)
{
	struct sensor_i2c_chip_info 	*chip;
	chip = kzalloc(sizeof(struct sensor_i2c_chip_info), GFP_KERNEL);
	if(chip == NULL)
	{
		sensor_dbg("\n tcc_sensor_i2c  :  no chip info. \n");
		return -ENOMEM;
	}

	chip->client = client;
	i2c_set_clientdata(client, chip);
	//sensor_i2c_client = client;

	return 0;
}