I2C驱动分析

一，添加I2C平台设备
linux的设备模型将设备分成了driver，device两大部分，driver即是设备的驱动，device即是硬件设备的具体描述，比如说：设备所拥有的中断，地址等，这里分析一下I2C驱动中device，也即i2c_client的注册，driver 也即是i2c_driver的注册，
i2c_client 的注册，是由

int __init
i2c_register_board_info(int busnum,
    struct i2c_board_info const *info, unsigned len)

函数 注册一个 i2c_board_info结构体来完成的。busnum 是总线编号，len设备个数

struct i2c_board_info {
    char        type[I2C_NAME_SIZE];
    unsigned short    flags;
    unsigned short    addr;
    void        *platform_data;
    struct dev_archdata    *archdata;
    struct device_node *of_node;
    int        irq;
};

其中最主要的两个参数是type即驱动设备名称，这个名字要与后面提到的i2c_device_id结构体中的名字一致，addr从设备地址。
到此I2C平台设备添加完成。
二，注册I2C驱动
1，初始化一个i2c_driver结构体，定义如下

struct i2c_driver {
    unsigned int class;

    /* Notifies the driver that a new bus has appeared or is about to be
     * removed. You should avoid using this, it will be removed in a
     * near future.
     */
    int (*attach_adapter)(struct i2c_adapter *) __deprecated;
    int (*detach_adapter)(struct i2c_adapter *) __deprecated;

    /* Standard driver model interfaces */
    int (*probe)(struct i2c_client *, const struct i2c_device_id *);
    int (*remove)(struct i2c_client *);

    /* driver model interfaces that don't relate to enumeration */
    void (*shutdown)(struct i2c_client *);
    int (*suspend)(struct i2c_client *, pm_message_t mesg);
    int (*resume)(struct i2c_client *);

    /* Alert callback, for example for the SMBus alert protocol.
     * The format and meaning of the data value depends on the protocol.
     * For the SMBus alert protocol, there is a single bit of data passed
     * as the alert response's low bit ("event flag").
     */
    void (*alert)(struct i2c_client *, unsigned int data);

    /* a ioctl like command that can be used to perform specific functions
     * with the device.
     */
    int (*command)(struct i2c_client *client, unsigned int cmd, void *arg);

    struct device_driver driver;
    const struct i2c_device_id *id_table;

    /* Device detection callback for automatic device creation */
    int (*detect)(struct i2c_client *, struct i2c_board_info *);
    const unsigned short *address_list;
    struct list_head clients;
};

.driver.name  驱动名字。不必和device的name相同。另外几个主要成员 是probe,remove,id_table,

struct i2c_device_id *id_table 定义实例如下
struct i2c_device_id static const struct i2c_device_id rx8010_id[] = {
    { "rx8010", 0 },// 此名称必须与 i2c_board_info的type一致，系统依据此名称匹配设备和驱动
    { }
};id_table

调用函数 i2c_register_driver(THIS_MODULE, driver) 完成驱动注册。