I2C设备驱动的主要数据结构

1.内核中I2C相关代码可以分为以下三个层次:
(1)I2C主体框架.由i2c.h和i2c-core.c构成,它提供了核心数据结构定义,适配器驱动和设备驱动的注册,注销管理.
(2)I2C总线适配器驱动.定义描述总线适配器的i2c_adapter数据结构,实现在具体i2c适配上的i2c总线通信方法,它是由i2c_algorithm数据结构进行描述的.
(3) I2C设备驱动:定义描述具体设备的i2c_client和可能的么有数据结构,借助i2c框架的i2c_probe函数实现注册设备的 attach_adapter方法,提供设备可能使用的地址范围,以及设备地址检测成功后创建i2c_client数据结构回调函数.
2. I2C设备驱动程序中重要的几个数据结构.
(1)这是一个与Linux下所有设备驱动都相关的数据结构.

struct device_driver {
    char            * name;
    struct bus_type        * bus;

    struct completion    unload_done;
    struct kobject        kobj;
    struct list_head    devices;

    struct module         * owner;

    int    (*probe)    (struct device * dev);
    int     (*remove)    (struct device * dev);
    void    (*shutdown)    (struct device * dev);
    int    (*suspend)    (struct device * dev, u32 state, u32 level);
    int    (*resume)    (struct device * dev, u32 level);
};
(2)attach_adapter 回调函数在安装i2c启程驱动程序模块时,或者在安装i2c适配器驱动程序模块时被调用,用于检测,认领设备并为设备分配i2_client及相应的私有 数据结构;而detach_client即是用来释放上面两个函数即创建的私有数据结构.

/*
 * A driver is capable of handling one or more physical devices present on
 * I2C adapters. This information is used to inform the driver of adapter
 * events.
 */

struct i2c_driver {
    struct module *owner;
    char name[32];
    int id;
    unsigned int class;
    unsigned int flags;        /* div., see below        */

    /* Notifies the driver that a new bus has appeared. This routine
     * can be used by the driver to test if the bus meets its conditions
     * & seek for the presence of the chip(s) it supports. If found, it
     * registers the client(s) that are on the bus to the i2c admin. via
     * i2c_attach_client.
     */
    int (*attach_adapter)(struct i2c_adapter *);
    int (*detach_adapter)(struct i2c_adapter *);

    /* tells the driver that a client is about to be deleted & gives it
     * the chance to remove its private data. Also, if the client struct
     * has been dynamically allocated by the driver in the function above,
     * it must be freed here.
     */
    int (*detach_client)(struct i2c_client *);
    
    /* 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;
    struct list_head list;
};
(3)attach_adapter 回调函数在安装i2c启程驱动程序模块时,或者在安装i2c适配器驱动程序模块时被调用,用于检测,认领设备并为设备分配i2_client及相应的私有 数据结构;而detach_client即是用来释放上面两个函数即创建的私有数据结构.


struct i2c_client {
    int id;
    unsigned int flags;   /* div., see below        */
    unsigned int addr;   /* chip address NOTE: 7bit */
                 /* addresses are stored in the    */
                 /* _LOWER_ 7 bits of this char    */
   /* addr: unsigned int to make lm_sensors i2c-isa adapter work more cleanly. It does not take any more memory space, due to alignment considerations */
    struct i2c_adapter *adapter; /* the adapter we sit on    */
    struct i2c_driver *driver;   /* and our access routines    */
    int usage_count; /* How many accesses currently */
                    /* to the client        */
    struct device dev;/* the device structure */
    struct list_head list;
    char name[I2C_NAME_SIZE];
    struct completion released;
};

3.下面用tlv320aic33驱动程序来大概说一下整个过流程:
(1)先定义i2c_driver和i2c_client这两个数据结构.然后用面这个函数来初始化这个数据结构.

static int
aic33_i2c_init(void)
{
    int err;
    struct i2c_driver *driver = &aic33_i2c_dev.driver;

    driver->owner = THIS_MODULE;
    strlcpy(driver->name, "Audio Codec I2C driver", sizeof(driver->name));
    driver->id = I2C_DRIVERID_EXP0;
    driver->flags = I2C_DF_NOTIFY;
    driver->attach_adapter = aic33_i2c_probe_adapter;
    driver->detach_client = aic33_i2c_detach_client;

    err = i2c_add_driver(driver);
    if (err) {
        printk(KERN_ERR "Failed to register Audio Codec I2C client.\n");
        return err;
    }
    return 0;
}