【Linux高级驱动】I2C驱动框架分析

1.i2c-dev.c(i2c设备驱动组件层)

    功能:1)给用户提供接口

i2c_dev_init  //入口函数
 /*申请主设备号*/

register_chrdev(I2C_MAJOR(89), "i2c", &i2cdev_fops);
 /*创建一个设备类*/
 i2c_dev_class = class_create(THIS_MODULE, "i2c-dev");
 /*注册一个i2c驱动*/
 i2c_add_driver(&i2cdev_driver);
  i2c_register_driver(THIS_MODULE, driver);
   /*指定总线类型*/
   driver->driver.bus = &i2c_bus_type;
   /*驱动注册
    *1.将i2c驱动加入i2c总线的驱动链表
    *2.搜索设备链表,实现匹配,根据i2c总线的匹配原理:必须要求i2c驱动结构体中实现id_table
    *  但是,i2c驱动结构体中并没有实现id_table,所以永远都匹配失败
    */
   driver_register(&driver->driver);
    
   /*搜索适配器链表,每搜索一个适配器,都会调用__process_new_driver函数
    *在此函数中,又会调用i2c驱动中的,attach_adapter函数
    */
   bus_for_each_dev(&i2c_bus_type, NULL, driver, __process_new_driver);
   __process_new_driver  //此函数可能会被调用多次
    i2c_do_add_adapter(data, to_i2c_adapter(dev));
     if (driver->attach_adapter) {
      /* We ignore the return code; if it fails, too bad */
      driver->attach_adapter(adap);    //i2cdev_attach_adapter
     }

static const struct file_operations i2cdev_fops = {
 .owner  = THIS_MODULE,
 .llseek  = no_llseek,
 .read  = i2cdev_read,
 .write  = i2cdev_write,
 .unlocked_ioctl = i2cdev_ioctl,
 .open  = i2cdev_open,
 .release = i2cdev_release,
};
static struct i2c_driver i2cdev_driver = {
 .driver = {
  .name = "dev_driver",
 },
 .attach_adapter = i2cdev_attach_adapter,
 .detach_adapter = i2cdev_detach_adapter,
};

 

2.i2c-core.c(i2c核心层组件)

    功能:1)注册一条i2c总线
         2)提供基本的接口函数,用来建立上层与下层的连接

i2c_init  //入口函数
 /*注册I2C总线*/
 bus_register(&i2c_bus_type);
   
struct bus_type i2c_bus_type = {  //实际的物理总线,I2C总线
 .name  = "i2c",
 .match  = i2c_device_match,  //匹配函数
 .probe  = i2c_device_probe,
 .remove  = i2c_device_remove,
 .shutdown = i2c_device_shutdown,
 .pm  = &i2c_device_pm_ops,
};
static int i2c_device_match(struct device *dev, struct device_driver *drv)
{
 struct i2c_client *client = i2c_verify_client(dev);
 struct i2c_driver *driver;
 if (!client)
  return 0;
 driver = to_i2c_driver(drv);
 /* match on an id table if there is one */
 if (driver->id_table)
  return i2c_match_id(driver->id_table, client) != NULL;
    while (id->name[0]) {
     if (strcmp(client->name, id->name) == 0)
      return id;
     id++;
    }
 return 0;
}

涉及的重要结构体:

struct i2c_client {     //表示一个i2c设备
 unsigned short flags;   /* div., see below  */
 unsigned short addr;   /*器件地址*/
 char name[I2C_NAME_SIZE];  /*名字*/
 struct i2c_adapter *adapter; /*所属适配器,所属控制器*/
 struct i2c_driver *driver;  /*设备驱动*/
 struct device dev;    /* the device structure  */
 int irq;      /* irq issued by device  */
 struct list_head detected;
};
struct i2c_driver {     //用来表示i2c驱动
 unsigned int class;
 /* Notifies the driver that a new bus has appeared or is about to be
  * removed. You should avoid using this if you can, it will probably
  * be removed in a near future.
  */
 int (*attach_adapter)(struct i2c_adapter *);
 int (*detach_adapter)(struct i2c_adapter *);
 /*probe函数:初始化工作,设备检测,*/
 int (*probe)(struct i2c_client *, const struct i2c_device_id *);
 int (*remove)(struct i2c_client *);
 struct device_driver driver;    //设备驱动
 const struct i2c_device_id *id_table;  //指定此驱动能为哪些设备服务
 ...
 ...
};
struct i2c_adapter {    //表示一个i2c适配器/i2c控制器
 const struct i2c_algorithm *algo; /* the algorithm to access the bus */
  /*操作方法*/
  int (*master_xfer)(struct i2c_adapter *adap, struct i2c_msg *msgs,int num);
 int nr;     /*适配器的号码*/
 ...
 ...
};
struct i2c_msg {     //表示一个i2c数据包
 __u16 addr;      /*设备地址*/
 __u16 flags;     /*表示:1-表示读包 0-表示写包*/
 __u16 len;      /*数据包的长度*/
 __u8 *buf;      /*真正的数据*/
 ...
 ...
};

涉及的重要函数接口:

/*注册一个i2c控制器*/
int i2c_add_adapter(struct i2c_adapter *adapter)
int i2c_del_adapter(struct i2c_adapter *adap)
/*注册i2c驱动*/
int i2c_add_driver(struct i2c_driver *driver)
int i2c_add_numbered_adapter(struct i2c_adapter *adap)
int i2c_del_numbered_adapter(struct i2c_adapter *adap)
extern int i2c_del_driver(struct i2c_driver *driver);
/*接收i2c数据包*/
int i2c_master_recv(struct i2c_client *client, char *buf, int count)
/*发送i2c数据包*/
int i2c_master_send(struct i2c_client *client, const char *buf, int count)
/*提交i2c数据包到总线驱动层*/
int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)

 

3.busses目录:i2c总线驱动/i2c控制器驱动/i2c适配器驱动

    i2c-s3c2410.c

    功能:1)实现对i2c控制器的初始化
         2)实现操作方法(实现i2c协议,完成数据的发送)

如何用通用接口驱动来操作i2c设备

open

app:  open("/dev/i2c-0", O_RDWR);
=====================================
sys:  sys_open
   ...
   ...
i2c-dev.c struct file_operations i2cdev_fops
    .open  = i2cdev_open,
     /*构建一个i2c_client*/
     struct i2c_client *client; 
     struct i2c_adapter *adap;  
     /*获取适配器*/
     adap = i2c_get_adapter(i2c_dev->adap->nr);
     client = kzalloc(sizeof(*client), GFP_KERNEL);
     client->driver = &i2cdev_driver;  //指定i2c设备驱动
     client->adapter = adap;     //指定适配器
     file->private_data = client;

ioctl

app:  ioctl(fd, I2C_SLAVE, 0x48)
==============================================
sys:  sys_ioctl
   ...
   ...
i2c-dev.c struct file_operations i2cdev_fops
    .unlocked_ioctl = i2cdev_ioctl,
     /*获取i2c_client*/
     struct i2c_client *client = file->private_data;
     switch (cmd) {
      case I2C_SLAVE:    I2C_M_TEN:是否为10位寻址的设备
       if ((arg > 0x3ff) ||(((client->flags & I2C_M_TEN) == 0) && arg > 0x7f))
        return -EINVAL;
       client->addr = arg;  //0x48
     }

write

app:  write(fd, wbuf, 1)
===============================================
sys:  sys_write
   ...
   ...
i2c-dev.c struct file_operations i2cdev_fops
    .write  = i2cdev_write,
     /*获取i2c_client*/
     struct i2c_client *client = file->private_data;
     char *tmp;
     tmp = kmalloc(count, GFP_KERNEL);
     copy_from_user(tmp, buf, count)
     
     /*发送数据到核心层*/
i2c-core.c   i2c_master_send(client, tmp, count);
      struct i2c_msg msg;   //表示i2c数据包
      /*填充数据包*/
      msg.addr = client->addr;    //0x48
      msg.flags = client->flags & I2C_M_TEN; //写
      msg.len = count;      //1
      msg.buf = (char *)buf;     //wbuf 0x0
      /*提交数据给总线驱动层*/
      i2c_transfer(adap, &msg, 1);
       if (adap->algo->master_xfer) 
i2c_s3c2410.c      adap->algo->master_xfer(adap, msgs, num);   //s3c24xx_i2c_xfer
         s3c24xx_i2c_xfer
          

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