和菜鸟一起学linux总线驱动之初识i2c驱动主要结构

       和spi一样，了解了协议后，还是看看具体的linux kernel中的i2c的一些数据结构吧。

在include/linux/i2c.h中

主要是以下这些数据结构：

struct i2c_msg;

struct i2c_algorithm;

struct i2c_adapter;

struct i2c_client;

struct i2c_driver;

union i2c_smbus_data;

struct i2c_board_info;

 

 

I2C的driver

 

struct i2c_driver {

       unsigned int class;//I2C设备类型

 

       /* 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; //要检测的I2C地址

       struct list_head clients; 

};

 

I2C的client

识别单个设备连接到一个总线上。

struct i2c_client {

       unsigned short flags;             /* div., see below          */

       unsigned short addr;             /* chip address - NOTE: 7bit */

                                   /* addresses are stored in the  */

                                   /* _LOWER_ 7 bits              */

       char name[I2C_NAME_SIZE];   //设备名

       struct i2c_adapter *adapter;   /* the adapter we sit on  *///I2C主控制器

       struct i2c_driver *driver;       /* and our access routines      *///I2C设备驱动

       struct device dev;          /* the device structure           */从机的驱动类型设备节点

       int irq;                  /* irq issued by device          */ //中断号

       struct list_head detected;     

};

 

I2C的board_info

添加i2c设备的信息

struct i2c_board_info {

       char        type[I2C_NAME_SIZE]; //I2C设备名

       unsigned short flags;      //i2c_client.flags的初始化

       unsigned short addr;       //设备地址

       void        *platform_data;

       struct dev_archdata *archdata;

       struct device_node *of_node;

       int          irq;  //设备中断号

};

 

I2C的algorithm

所有的驱动时序都是在算法中实现的

 

struct i2c_algorithm {

       /* If an adapter algorithm can't do I2C-level access, set master_xfer

          to NULL. If an adapter algorithm can do SMBus access, set

          smbus_xfer. If set to NULL, the SMBus protocol is simulated

          using common I2C messages */

       /* master_xfer should return the number of messages successfully

          processed, or a negative value on error */

       int (*master_xfer)(struct i2c_adapter *adap, struct i2c_msg *msgs,

                        int num);

       int (*smbus_xfer) (struct i2c_adapter *adap, u16 addr,

                        unsigned short flags, char read_write,

                        u8 command, int size, union i2c_smbus_data *data);

 

       /* To determine what the adapter supports */

       u32 (*functionality) (struct i2c_adapter *);

};

 

 

I2C的adapter

主控制器，用以鉴定i2c总线

struct i2c_adapter {

       struct module *owner;

       unsigned int class;           /* classes to allow probing for */

       const struct i2c_algorithm *algo; /* the algorithm to access the bus */

       void *algo_data;

 

       /* data fields that are valid for all devices    */

       struct rt_mutex bus_lock;

 

       int timeout;                   /* in jiffies */

       int retries;

       struct device dev;          /* the adapter device */

 

       int nr;

       char name[48];

       struct completion dev_released;

 

       struct mutex userspace_clients_lock;

       struct list_head userspace_clients;

};.

 

I2C的msg

在调用i2c_transfer的时候发送或者接收数据

struct i2c_msg {

       __u16 addr;    /* slave address*/

       __u16 flags;   //读写等的标志

#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  *//发送和接收的buf的长度/

       __u8 *buf;             /* pointer to msg data*///发送或者接收的buf

};

 

I2C的gpio模拟用的platform_data

struct i2c_gpio_platform_data {

       unsigned int    sda_pin;

       unsigned int    scl_pin;

       int          udelay;

       int          timeout;

       unsigned int    sda_is_open_drain:1;

       unsigned int    scl_is_open_drain:1;

       unsigned int    scl_is_output_only:1;

};