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首先，如果对platform设备和驱动的注册机制不熟悉的话，可以先看一下大神的博客
http://blog.csdn.net/zqixiao_09/article/details/50888795

一、下面逐一分析一下每一个函数的功能
1、platform_device_register //把设备注册到platform bus上

1)platform_device_add            
2)pdev->dev.bus = &platform_bus_type; //指明设备要挂载总线类型
3)device_add
4)bus_add_device        //把设备放到相应的总线上面
5)bus_probe_device
6)device_attach       //尝试绑定相应的驱动
7)bus_for_each_drv
8)__device_attach
9)driver_match_device  //调用platform_match匹配相应的驱动,先匹配id table，再返回比较驱动的名字
//1、注册设备前，驱动已经注册，那么则会继续执行相应设备的probe函数
//2、如果注册设备前，驱动没有被注册，那么就仅把设备注册到总线上   
10)driver_probe_device(drv, dev) 
11)really_probe(dev, drv)                                       
12)dev->bus->probe(dev)/drv->probe(dev)  //执行驱动的probe，对设备进行初始化
13)put_device       //把设备放进内核

2、platform_driver_register //把驱动注册到platform bus上

1)drv->driver.bus = &platform_bus_type;//指明驱动要挂载总线类型
2)driver_register
3)bus_add_driver    //把driver添加到bus上面
4)driver_attach                         
5)bus_for_each_dev  //查找相应的设备是否已经在总线上注册  
6)__driver_attach(struct device * dev, void * data) 
7)driver_match_device(drv, dev) //与上面platform_match的一样
//1、注册驱动前，设备已经注册，那么则会继续执行相应设备的probe函数
//2、如果注册驱动前，设备没有被注册，那么就仅把驱动注册到总线上
8)driver_probe_device(drv, dev) 
9)really_probe(dev, drv)                                        
10)dev->bus->probe(dev)/drv->probe(dev)  //执行驱动的probe，对设备进行初始化
11)klist_add_tail(&priv->knode_bus, &bus->p->klist_drivers);  //把driver放在bus

下面分析一下关键函数

    int bus_add_driver(struct device_driver *drv){......if (drv->bus->p->drivers_autoprobe) {error = driver_attach(drv); //驱动开始匹配设备if (error)goto out_unregister;}......}int driver_attach(struct device_driver *drv){return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach); //在bus上面轮询匹配设备}//遍历bus的函数int bus_for_each_dev(struct bus_type *bus, struct device *start,void *data, int (*fn)(struct device *, void *)){struct klist_iter i;struct device *dev;int error = 0;if (!bus)return -EINVAL;klist_iter_init_node(&bus->p->klist_devices, &i,(start ? &start->p->knode_bus : NULL));while ((dev = next_device(&i)) && !error)error = fn(dev, data);  klist_iter_exit(&i);return error;}//实际的匹配函数static int __driver_attach(struct device *dev, void *data){struct device_driver *drv = data;/** Lock device and try to bind to it. We drop the error* here and always return 0, because we need to keep trying* to bind to devices and some drivers will return an error* simply if it didn't support the device.** driver_probe_device() will spit a warning if there* is an error.*///如果没有找到相应的设备 则退出if (!driver_match_device(drv, dev)) return 0;//如果找到相应的设备 则执行driver的probe对设备进行初始化工作if (dev->parent)    /* Needed for USB */device_lock(dev->parent);device_lock(dev);if (!dev->driver)driver_probe_device(drv, dev);device_unlock(dev);if (dev->parent)device_unlock(dev->parent);return 0;}

3、device_register
其实device_register就是platform_device_register的父本，platform_device_register在device_register的基础上添加了platform_device一些个性的内容，如果没有把设备注册成platform device的情况，一般都会使用device_register来注册设备，如misc_register注册设备时。

4、driver_register
driver_register也一样，就是platform_driver_register的父本。

二、下面结合实例说明一下

#include <linux/init.h>
#include <linux/module.h>
#include <linux/device.h> 
#include <linux/platform_device.h>
#include <linux/miscdevice.h>
#include <linux/fs.h>#define DRIVER_NAME "hello_driver"//用于在总线上适配的驱动名字
#define DEVICE_NAME "hello_device"//生成的设备节点名字static int hello_release(struct inode *inode, struct file *file){printk("hello release\n");return 0;
}static int hello_open(struct inode *inode, struct file *file){printk("hello open\n");return 0;
}static struct file_operations hello_ops = {.owner = THIS_MODULE,.open = hello_open,.release = hello_release,
};static  struct miscdevice hello_dev = {.minor = MISC_DYNAMIC_MINOR,.name = DEVICE_NAME,//设备节点名.fops = &hello_ops,
};//如果总线匹配成功 就会执行probe函数
static int hello_probe(struct platform_device *pdv){printk("hello_probe\n");misc_register(&hello_dev);return 0;
}static int hello_remove(struct platform_device *pdv){printk("hello_remove\n");misc_deregister(&hello_dev);return 0;
}static void hello_shutdown(struct platform_device *pdv){;
}static int hello_suspend(struct platform_device *pdv,pm_message_t pmt){return 0;
}static int hello_resume(struct platform_device *pdv){return 0;
}//创建设备
static struct platform_device hello_device=  
{  .name = DRIVER_NAME,  //用于总线匹配.id = -1,  
}; //创建驱动
struct platform_driver hello_driver = {.probe = hello_probe,.remove = hello_remove,.shutdown = hello_shutdown,.suspend = hello_suspend,.resume = hello_resume,.driver = {.name = DRIVER_NAME, //用于总线匹配.owner = THIS_MODULE,}
};static int hello_init(void)
{int DriverState;platform_device_register(&hello_device);printk(KERN_EMERG "hello_init!\n");//打印信息使用dmesg查看//执行platform_driver_register后 适配完 就会执行//hello_probe，即先打印hello_probe信息，才会打印//tDriverState信息DriverState = platform_driver_register(&hello_driver);printk(KERN_EMERG "\tDriverState is %d\n",DriverState);return 0;
}static void hello_exit(void)
{printk(KERN_EMERG "hello_exit!\n");platform_driver_unregister(&hello_driver);  platform_device_unregister(&hello_device); 
}module_init(hello_init);
module_exit(hello_exit);
MODULE_LICENSE("GPL");