【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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