i2c_drivers个人分析

archarmmach-mx6oard-mx6q_sabresd.c

static struct i2c_board_info i2c_board_info_rtc[] __initdata = {
    //isl1208 does not work on the 1st board that's sent to Korea, but we should enbaled it later.
#if 1
    {
        I2C_BOARD_INFO("isl1208", 0x6F),
        //.irq = gpio_to_irq(CYNO_GPIO_R10),
    },
#else
    //pcf8563 is no longer usned.
    {
        I2C_BOARD_INFO("pcf8563", 0x51),
        //.irq = gpio_to_irq(CYNO_GPIO_R10),
    },
#endif
};

 这个busnum号决定了adapter->nr之间的关系，如果相等这把这个总线设备和适配器连接起来

i2c_register_board_info(2, i2c_board_info_rtc, ARRAY_SIZE(i2c_board_info_rtc));

下面我们再来分析下i2c_register_board_info这个文件的定义

在drivers/i2c/i2c-boardinfo.c文件中我们找到这个函数的定义：

int __init
i2c_register_board_info(int busnum, //这个busnum号决定了adapter->nr之间的关系，如果相等这把这个总线设备和适配器连接起来
    struct i2c_board_info const *info, unsigned len)
{
    int status;

    down_write(&__i2c_board_lock);

    /* dynamic bus numbers will be assigned after the last static one */
    if (busnum >= __i2c_first_dynamic_bus_num)
        __i2c_first_dynamic_bus_num = busnum + 1;

    for (status = 0; len; len--, info++) {
        struct i2c_devinfo    *devinfo;

        devinfo = kzalloc(sizeof(*devinfo), GFP_KERNEL);
        if (!devinfo) {
            pr_debug("i2c-core: can't register boardinfo!
");
            status = -ENOMEM;
            break;
        }

        devinfo->busnum = busnum;
        devinfo->board_info = *info;
        list_add_tail(&devinfo->list, &__i2c_board_list);
    }

    up_write(&__i2c_board_lock);

    return status;
}

在这个函数里面定义了bus_num以及RTC相关信息

下面我们针对这个设备具体分析

我们在/drivers/rtc/rtc-isl1208.c这个文件

static const struct i2c_device_id isl1208_id[] = {
{ "isl1208", 0 },
{ }
};
MODULE_DEVICE_TABLE(i2c, isl1208_id);

static struct i2c_driver isl1208_driver = {
.driver = {
.name = "rtc-isl1208",
},
.probe = isl1208_probe,
.remove = isl1208_remove,
.id_table = isl1208_id,
};

可以看到isl1208_driver真是这个设备所支持的驱动 

static int i2c_register_adapter(struct i2c_adapter *adap)
{
 int res = 0, dummy;

 mutex_init(&adap->bus_lock);    //初始化保护i2c适配器的互斥锁
 mutex_init(&adap->clist_lock);    //初始化保护adap->clients的锁
 INIT_LIST_HEAD(&adap->clients); //初始化i2c适配器上介入的设备（client）链表

 mutex_lock(&core_lock);

//初始化adap->dev然后注册该设备
 if (adap->dev.parent == NULL) {
  adap->dev.parent = &platform_bus;
  pr_debug("I2C adapter driver [%s] forgot to specify "
    "physical device ", adap->name);
 }
 sprintf(adap->dev.bus_id, "i2c-%d", adap->nr);
 adap->dev.release = &i2c_adapter_dev_release;
 adap->dev.class = &i2c_adapter_class;
 res = device_register(&adap->dev);
 if (res)
  goto out_list;

 dev_dbg(&adap->dev, "adapter [%s] registered ", adap->name);

//适配器驱动注册进内核后，对系统中现有的两种设备进行绑定。

 
 if (adap->nr < __i2c_first_dynamic_bus_num)//__i2c_first_dynamic_bus_num表示第一个动态分配的设备号
  i2c_scan_static_board_info(adap);  //如果适配器号和设备好一致，则会进行设备和适配器的绑定，如果不一致，则会执行下面的函数

 
 dummy = bus_for_each_drv(&i2c_bus_type, NULL, adap, 
     i2c_do_add_adapter);

out_unlock:
 mutex_unlock(&core_lock);
 return res;

out_list:
 idr_remove(&i2c_adapter_idr, adap->nr);
 goto out_unlock;
}

注册适配器后，开始调用  i2c_scan_static_board_info(adap);查找i2c_board_info的相关设备的注册信息

__i2c_board_list中查找 我们在板级文件中以把相关i2c——device的信息注册到这个双向链表中了。。struct i2c_devinfo相对比，如果找到了，就会调用i2c_new_device（）把device和适配器绑定在一起，

static void i2c_scan_static_board_info(struct i2c_adapter *adapter)
{
 struct i2c_devinfo *devinfo;

 mutex_lock(&__i2c_board_lock);
 list_for_each_entry(devinfo, &__i2c_board_list, list) {
  if (devinfo->busnum == adapter->nr //如果device编号和adapter编号一致，则会调用i2c_new_device，把device和adapter绑定在一起
    && !i2c_new_device(adapter,
      &devinfo->board_info))
   printk(KERN_ERR "i2c-core: can't create i2c%d-x ",
    i2c_adapter_id(adapter),
    devinfo->board_info.addr);
 }
 mutex_unlock(&__i2c_board_lock);
}

下面来分析这个i2c_new_device(struct i2c_adapter *adap, struct i2c_board_info const *info)
struct i2c_client *
i2c_new_device(struct i2c_adapter *adap, struct i2c_board_info const *info)
{
struct i2c_client *client;
int status;

client = kzalloc(sizeof *client, GFP_KERNEL);
if (!client)
return NULL;

client->adapter = adap; //在这个地方适配器和i2c_device 绑定

client->dev.platform_data = info->platform_data;

if (info->archdata)
client->dev.archdata = *info->archdata;

client->flags = info->flags;
client->addr = info->addr;//这个地方决定了设备的地址
client->irq = info->irq;

strlcpy(client->name, info->type, sizeof(client->name));

/* Check for address validity */
status = i2c_check_client_addr_validity(client);
if (status) {
dev_err(&adap->dev, "Invalid %d-bit I2C address 0x%02hx ",
client->flags & I2C_CLIENT_TEN ? 10 : 7, client->addr);
goto out_err_silent;
}

/* Check for address business */
status = i2c_check_addr_busy(adap, client->addr);
if (status)
goto out_err;

client->dev.parent = &client->adapter->dev;
client->dev.bus = &i2c_bus_type;
client->dev.type = &i2c_client_type;
client->dev.of_node = info->of_node;

dev_set_name(&client->dev, "%d-%04x", i2c_adapter_id(adap),
client->addr);
status = device_register(&client->dev);这个设备被绑定到了总线上面，但是这个设备所支持的drivers呢？？？？？？

if (status)
goto out_err;

dev_dbg(&adap->dev, "client [%s] registered with bus id %s ",
client->name, dev_name(&client->dev));

return client;

out_err:
dev_err(&adap->dev, "Failed to register i2c client %s at 0x%02x "
"(%d) ", client->name, client->addr, status);
out_err_silent:
kfree(client);
return NULL;
}

下面分析 dummy = bus_for_each_drv(&i2c_bus_type, NULL, adap, i2c_do_add_adapter);这个函数

static int i2c_do_add_adapter(struct i2c_driver *driver,
struct i2c_adapter *adap)
{
/* Detect supported devices on that bus, and instantiate them */
i2c_detect(adap, driver); 通过这个函数又会把设配器和设备绑定在一起，这次依靠的是driver的地址是否存在而绑定的

/* Let legacy drivers scan this bus for matching devices */
if (driver->attach_adapter) {
dev_warn(&adap->dev, "%s: attach_adapter method is deprecated ",
driver->driver.name);
dev_warn(&adap->dev, "Please use another way to instantiate "
"your i2c_client ");
/* We ignore the return code; if it fails, too bad */
driver->attach_adapter(adap);
}
return 0;
}

在struct i2c_adapter 注册到内核中后，内核时怎样把已经注册进系统中的i2c设备设备与刚注册进内核的适配器进行绑定的。分两种情况一是在板级用 i2c_register_board_info注册的，其二是通过各种struct i2c_driver注册的。其中驱动注册又有两种方法，一种是新的总线式驱动一种是老式的，这里我们对老式的方法不做介绍，老式的方法在内核中也慢慢的消亡。

可能很多人有以后这个该死的adapter什么时候注册，那我现在说先注册顺序（讲解针对板级文件中设备的注册分析）

步骤1：i2c_register_board_info(2, i2c_board_info_rtc, ARRAY_SIZE(i2c_board_info_rtc));

注册这个板级文件后就会把这个device的相关信息存储到__i2c_board_list

步骤2：对于静态的注册adapter这个适配器，这个早就设定好了，所以直接注册，在这个函数i2c_register_adapter的后面几个函数就会决定设配器和device的绑定

• 
  int i2c_add_numbered_adapter(struct i2c_adapter *adap)  
• {  
•     int id;  
•     int status;  
•   
•     if (adap->nr & ~MAX_ID_MASK)  
•         return -EINVAL;  
•   
• retry:  
•     if (idr_pre_get(&i2c_adapter_idr, GFP_KERNEL) == 0)  
•         return -ENOMEM;  
•   
•     mutex_lock(&core_lock);  
•     /* "above" here means "above or equal to", sigh; 
•      * we need the "equal to" result to force the result 
•      */  
•     status = idr_get_new_above(&i2c_adapter_idr, adap, adap->nr, &id);  
•     if (status == 0 && id != adap->nr) {  
•         status = -EBUSY;  
•         idr_remove(&i2c_adapter_idr, id);  
•     }  
•     mutex_unlock(&core_lock);  
•     if (status == -EAGAIN)  
•         goto retry;  
•   
•     if (status == 0)  
•         status = i2c_register_adapter(adap);  
•     return status;  
• }  

 if (adap->nr < __i2c_first_dynamic_bus_num)//__i2c_first_dynamic_bus_num表示第一个动态分配的设备号
  i2c_scan_static_board_info(adap);  //如果适配器号和设备好一致，则会进行设备和适配器的绑定，如果不一致，则会执行下面的函数

 dummy = bus_for_each_drv(&i2c_bus_type, NULL, adap, 
     i2c_do_add_adapter);

 步骤3：现在设配器和设备已经绑定了，那设备的驱动什么时候能找到这个设备呢，我们继续分析

static struct i2c_driver isl1208_driver = {
.driver = {
.name = "rtc-isl1208",
},
.probe = isl1208_probe,
.remove = isl1208_remove,
.id_table = isl1208_id,
};

在driver/rtc/rtc-isli1208.c文件中最好几行代码会注册这个驱动，

static int __init
isl1208_init(void)
{
return i2c_add_driver(&isl1208_driver);
}

static void __exit
isl1208_exit(void)
{
i2c_del_driver(&isl1208_driver);
}

我们再来分析这个i2c_add_driver函数，也许会有一点感悟

static inline int i2c_add_driver(struct i2c_driver *driver)
{
return i2c_register_driver(THIS_MODULE, driver);
}

/*
* An i2c_driver is used with one or more i2c_client (device) nodes to access
* i2c slave chips, on a bus instance associated with some i2c_adapter.
*/

int i2c_register_driver(struct module *owner, struct i2c_driver *driver)
{
int res;

/* Can't register until after driver model init */
if (unlikely(WARN_ON(!i2c_bus_type.p)))
return -EAGAIN;

/* add the driver to the list of i2c drivers in the driver core */
driver->driver.owner = owner;
driver->driver.bus = &i2c_bus_type;

/* When registration returns, the driver core
* will have called probe() for all matching-but-unbound devices.
*/
res = driver_register(&driver->driver);
if (res)
return res;

/* Drivers should switch to dev_pm_ops instead. *///这个地方会通过probe函数实现
if (driver->suspend)
pr_warn("i2c-core: driver [%s] using legacy suspend method ",
driver->driver.name);
if (driver->resume)
pr_warn("i2c-core: driver [%s] using legacy resume method ",
driver->driver.name);

pr_debug("i2c-core: driver [%s] registered ", driver->driver.name);

INIT_LIST_HEAD(&driver->clients);
/* Walk the adapters that are already present */
i2c_for_each_dev(driver, __process_new_driver);

return 0;

}

这个函数最下面有个i2c_for_each_dev(driver, __process_new_driver);这个地方不太理解，个人认为是那些可插拔设备寻找合适的适配器的方法

那到底设备和驱动是怎么结合到一起的呢，正确的设备是怎么配对正确的驱动的呢，这个最主要的功臣当然非probe函数莫属啦

那我们就来看看.probe = isl1208_probe这个探测函数吧

isl1208_probe(struct i2c_client *client, const struct i2c_device_id *id)
{
int rc = 0;
struct rtc_device *rtc;

if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))  //检查设备有哪些功能
return -ENODEV;

if (isl1208_i2c_validate_client(client) < 0) //判定这个设备是否是isl1208驱动所支持的设备，如过不是probe探测失败，
return -ENODEV;

dev_info(&client->dev,
"chip found, driver version " DRV_VERSION " ");

if (client->irq > 0) {
rc = request_threaded_irq(client->irq, NULL,isl1208_rtc_interrupt,IRQF_SHARED,
                                                       isl1208_driver.driver.name, client);//申请中断
if (!rc) {
device_init_wakeup(&client->dev, 1);
enable_irq_wake(client->irq);
} else {
dev_err(&client->dev,
"Unable to request irq %d, no alarm support ",
client->irq);
client->irq = 0;
}
}

rtc = rtc_device_register(isl1208_driver.driver.name,
&client->dev, &isl1208_rtc_ops,  THIS_MODULE); //关键中的关键终于到来，设备和驱动完美的结合，特备强调isl1208_rtc_ops，我们看看它代表什么。

////////////////////static const struct rtc_class_ops isl1208_rtc_ops = {

proc — 一个虚拟文件系统 
/proc 文件系统是一种内核和内核模块用来向进程 (process) 发送信息的机制 (所以叫做 /proc)。这个伪文件系统让你可以和内核内部数据结构进行交互，获取 有关进程的有用信息，在运行中 (on the fly) 改变设置 (通过改变内核参数)。 与其他文件系统不同，/proc 存在于内存之中而不是硬盘上。
///////////////////      .proc = isl1208_rtc_proc,  这些函数不都是定义在rtc-isl1208.c这个文件里面吗，此处的配置就是为了用户在调用rtc-isl1208这个设备的时候，能够对这个设备进行相应的读写操作
//////////////////       .read_time = isl1208_rtc_read_time,
/////////////////        .set_time = isl1208_rtc_set_time,
////////////////         .read_alarm = isl1208_rtc_read_alarm,

////////                  .set_alarm = isl1208_rtc_set_alarm,

///////////////////////        };

if (IS_ERR(rtc)) {
rc = PTR_ERR(rtc);
goto exit_free_irq;
}

i2c_set_clientdata(client, rtc);

rc = isl1208_i2c_get_sr(client);
if (rc < 0) {
dev_err(&client->dev, "reading status failed ");
goto exit_unregister;
}

if (rc & ISL1208_REG_SR_RTCF)
dev_warn(&client->dev, "rtc power failure detected, "
"please set clock. ");

rc = sysfs_create_group(&client->dev.kobj, &isl1208_rtc_sysfs_files);
if (rc)
goto exit_unregister;

return 0;

exit_unregister:
rtc_device_unregister(rtc);
exit_free_irq:
if (client->irq)
free_irq(client->irq, client);

return rc;
}

至此整个I2C的体系的分析就告一段落了，下一步，usb-mouse的分析哦

我敢肯定这里有很多不对的地方，如果被某人发现，请给我留言，谢谢 我定会更正