Table of Contents

1、I2C模型框图

2、设备信息层

2.1、非设备树形式

2.2、设备树形式

3、芯片控制器层adapter

3.1、控制器初始化 

3.2、控制器底层传输函数（起始，数据，应答，停止）

4、核心层core.c   i2c_bus

4.1、i2c_bus总线初始化

4.2、client（设备）和i2c_driver（设备驱动）匹配过程

4.2.1、创建client（设备）时匹配i2c_driver（驱动）过程

4.2.2、注册i2c_driver（驱动）时匹配client（设备）过程

4.3、总线探测probe

5、设备驱动层

5.1、设备驱动注册

5.2、设备驱动探测probe，并初始化i2c器件

5.3、数据传输

1、I2C模型框图

2、设备信息层

2.1、非设备树形式

  static struct mma7660_platform_data mma7660_pdata = {  .irq   = IRQ_EINT(25),  .poll_interval = 100,  .input_fuzz  = 4,  .input_flat  = 4, };  static struct i2c_board_info smdk4x12_i2c_devs3[] __initdata = {   {    I2C_BOARD_INFO("mma7660", 0x4c),   .platform_data = &mma7660_pdata,  }，  };

    i2c_register_board_info(3, smdk4x12_i2c_devs3,ARRAY_SIZE(smdk4x12_i2c_devs3));

                   list_add_tail(&devinfo->list, &__i2c_board_list);

2.2、设备树形式

’参考文章：I2C、SPI设备树驱动对设备子节点的处理

 &i2c_3 {     #address-cells = <1>;  #size-cells = <0>;  compatible = "samsung,s3c2440-i2c";  reg = <0x13890000 0x100>;  interrupts = <GIC_SPI 61 IRQ_TYPE_LEVEL_HIGH>;  clocks = <&clock CLK_I2C3>;  clock-names = "i2c";  samsung,i2c-sda-delay = <100>;  samsung,i2c-slave-addr = <0x10>;  samsung,i2c-max-bus-freq = <100000>;  pinctrl-0 = <&i2c3_bus>;  pinctrl-names = "default";  status = "okay";   codec: mma7660@1a {   compatible = "mma7660";   reg = <0x4c>;   clocks = <&pmu_system_controller 0>;   clock-names = "MCLK1";  }; };

3、芯片控制器层adapter

3.1、控制器初始化 

参考文章：I2C、SPI设备树驱动对设备子节点的处理

• 处理器有n个i2c控制器，那么就需要注册n个adapter
• 一个i2c控制器（接口）下可能接有多个i2c器件，因此一个adapter可能对应多个client

 static struct platform_driver s3c24xx_i2c_driver = {  .probe  = s3c24xx_i2c_probe,  .remove  = s3c24xx_i2c_remove,  .id_table = s3c24xx_driver_ids,  .driver  = {   .owner = THIS_MODULE,   .name = "s3c-i2c",   .pm = S3C24XX_DEV_PM_OPS,   .of_match_table = of_match_ptr(s3c24xx_i2c_match),  }, };  static int __init i2c_adap_s3c_init(void) {  return platform_driver_register(&s3c24xx_i2c_driver); }   static int s3c24xx_i2c_probe(struct platform_device *pdev) {     ret = s3c24xx_i2c_init(i2c); //初始化i2c硬件控制器     ret = i2c_add_numbered_adapter(&i2c->adap); //注册adapter，并转化设备信息为client    of_i2c_register_devices(&i2c->adap);      //转化设备树节点为client    return ret; }

3.2、控制器底层传输函数（起始，数据，应答，停止）

 static const struct i2c_algorithm s3c24xx_i2c_algorithm = {  .master_xfer  = s3c24xx_i2c_xfer,  .functionality  = s3c24xx_i2c_func, };  static int s3c24xx_i2c_xfer(struct i2c_adapter *adap,    struct i2c_msg *msgs, int num) {  struct s3c24xx_i2c *i2c = (struct s3c24xx_i2c *)adap->algo_data;     ret = s3c24xx_i2c_doxfer(i2c, msgs, num);  return -EREMOTEIO; }  static int s3c24xx_i2c_doxfer(struct s3c24xx_i2c *i2c,          struct i2c_msg *msgs, int num) {  unsigned long timeout;  int ret;   if (i2c->suspended)   return -EIO;   ret = s3c24xx_i2c_set_master(i2c);  if (ret != 0) {   dev_err(i2c->dev, "cannot get bus (error %d)n", ret);   ret = -EAGAIN;   goto out;  }   i2c->msg     = msgs;  i2c->msg_num = num;  i2c->msg_ptr = 0;  i2c->msg_idx = 0;  i2c->state   = STATE_START;   s3c24xx_i2c_enable_irq(i2c);  s3c24xx_i2c_message_start(i2c, msgs); //开始传输    }  

4、核心层core.c   i2c_bus

4.1、i2c_bus总线初始化

 struct bus_type i2c_bus_type = {  .name  = "i2c",  .match  = i2c_device_match,  .probe  = i2c_device_probe,  .remove  = i2c_device_remove,  .shutdown = i2c_device_shutdown,  .pm  = &i2c_device_pm_ops, };  static int __init i2c_init(void) {   retval = bus_register(&i2c_bus_type);  } 

4.2、client（设备）和i2c_driver（设备驱动）匹配过程

4.2.1、创建client（设备）时匹配i2c_driver（驱动）过程

 i2c_new_device   device_register  device_add   bus_probe_device    device_attach     bus_for_each_drv      __device_attach       driver_match_device //匹配        drv->bus->match       driver_probe_device //探测        really_probe         dev->bus->probe

4.2.2、注册i2c_driver（驱动）时匹配client（设备）过程

 i2c_add_driver  i2c_register_driver   driver_register    bus_add_driver     driver_attach      bus_for_each_dev       __driver_attach        driver_match_device //匹配         drv->bus->match        driver_probe_device //探测         really_probe          dev->bus->probe

4.3、总线探测probe

 static int i2c_device_probe(struct device *dev) {   driver = to_i2c_driver(dev->driver); //获得设备驱动  client->driver = driver;   //调用设备驱动probe函数  status = driver->probe(client, i2c_match_id(driver->id_table, client));    return status; }

5、设备驱动层

5.1、设备驱动注册

 static struct i2c_driver i2c_mma7660_driver = {  .driver  = {   .name = MMA7660_NAME,  },   .probe  = mma7660_probe,  .remove  = __devexit_p(mma7660_remove),  .suspend = mma7660_suspend,  .resume  = mma7660_resume,  .id_table = mma7660_ids, };  static int __init init_mma7660(void) {  int ret;   ret = i2c_add_driver(&i2c_mma7660_driver);  //注册驱动  printk(KERN_INFO "MMA7660 sensor driver registered.n");   return ret; }

5.2、设备驱动探测probe，并初始化i2c器件

 static int __devinit mma7660_probe(struct i2c_client *client,   const struct i2c_device_id *id) {  struct i2c_adapter *adapter = to_i2c_adapter(client->dev.parent); //得到i2c控制器信息    mma7660_initialize(client); //i2c器件初始化    ret = input_register_polled_device(mma7660_idev);//把i2c设备当输入设备访问    return 0; }

5.3、数据传输

整体调用过程

mma7660_read_xyz
       i2c_smbus_read_byte_data
               i2c_smbus_xfer
                      adapter->algo->smbus_xfer

详细调用过程 

 static void mma7660_dev_poll(struct input_polled_dev *dev) {  mma7660_report_abs(); }  static void mma7660_report_abs(void) {  int axis[3];  int i;   for (i = 0; i < 3; i++) {   mma7660_read_xyz(mma7660_client, i, &axis[i]);  }   input_report_abs(mma7660_idev->input, ABS_X, axis[0]);  input_report_abs(mma7660_idev->input, ABS_Y, axis[1]);  input_report_abs(mma7660_idev->input, ABS_Z, axis[2]);  input_sync(mma7660_idev->input);   //printk("3-Axis ... %3d, %3d, %3dn", axis[0], axis[1], axis[2]); }   static int mma7660_read_xyz(struct i2c_client *client, int idx, int *xyz) {     val = i2c_smbus_read_byte_data(client, idx + MMA7660_XOUT);     return 0; }   s32 i2c_smbus_read_byte_data(const struct i2c_client *client, u8 command) {  union i2c_smbus_data data;  int status;   status = i2c_smbus_xfer(client->adapter, client->addr, client->flags,     I2C_SMBUS_READ, command,     I2C_SMBUS_BYTE_DATA, &data);  return (status < 0) ? status : data.byte; }  s32 i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr, unsigned short flags,      char read_write, u8 command, int protocol,      union i2c_smbus_data *data) {      res = adapter->algo->smbus_xfer(adapter, addr, flags,        read_write, command,        protocol, data);      return res; }