LINUX设备管理模型-Platform总线(2)

上面一篇主要是介绍了怎么样用platform_device模型来管理设备，下面介绍下

platform_device和platform_driver的注册函数。这两个注册函数在drivers/base下的platform.c文件里面。

 

1.       首先来看platform_device_register函数。

platform_device_register-à platform_device_addà device_add

中途就是做了对资源的一些处理。

struct platform_device {

         const char        * name;

         u32            id;

         struct device    dev;

         u32            num_resources;

         struct resource        * resource;

};

 

int platform_device_register(struct platform_device * pdev)

{

         device_ initialize (&pdev->dev);

         return platform_device_add(pdev);

}

         首先是完成对dev的initialize。然后调用platform_device_add函数向系统添加一个platform设备。下面对该函数的关键部分注释。

 

int platform_device_add(struct platform_device *pdev)

{

         int i, ret = 0;

 

         if (!pdev)

                   return -EINVAL;

//让dev的parent指向 platform_bus,platform_bus也是作为一个设备向系统添加的。

         if (!pdev->dev.parent)

                   pdev->dev.parent = &platform_bus;

//dev所连接的总线是platform_bus_type

         pdev->dev.bus = &platform_bus_type;

 

         if (pdev->id != -1)

                   snprintf(pdev->dev.bus_id, BUS_ID_SIZE, "%s.%u", pdev->name, pdev->id);

         else

                   strlcpy(pdev->dev.bus_id, pdev->name, BUS_ID_SIZE);

 

         for (i = 0; i < pdev->num_resources; i++) {

                   struct resource *p, *r = &pdev->resource[i];

 

                   if (r->name == NULL)

                            r->name = pdev->dev.bus_id;

 

                   p = r->parent;

                   if (!p) {

                            if (r->flags & IORESOURCE_MEM)

                                     p = &iomem_resource;

                            else if (r->flags & IORESOURCE_IO)

                                     p = &ioport_resource;

                   }

//向系统注册mem和io两类资源，也就是检测是否与已经注册的资源冲突了。

                   if (p && insert_resource(p, r)) {

                            printk(KERN_ERR

                                   "%s: failed to claim resource %d\n",

                                   pdev->dev.bus_id, i);

                            ret = -EBUSY;

                            goto failed;

                   }

         }

 

         pr_debug("Registering platform device '%s'. Parent at %s\n",

                    pdev->dev.bus_id, pdev->dev.parent->bus_id);

//就是将设备注册到指定的bus_type,这个在以后的文章中在详细介绍

         ret = device_add(&pdev->dev);

         if (ret == 0)

                   return ret;

 

 failed:

         while (--i >= 0)

                   if (pdev->resource[i].flags & (IORESOURCE_MEM|IORESOURCE_IO))

                            release_resource(&pdev->resource[i]);

         return ret;

}

2.       下面来看看platform_driver_register的实现。

 

struct platform_driver {

         int (*probe)(struct platform_device *);

         int (*remove)(struct platform_device *);

         void (*shutdown)(struct platform_device *);

         int (*suspend)(struct platform_device *, pm_message_t state);

         int (*suspend_late)(struct platform_device *, pm_message_t state);

         int (*resume_early)(struct platform_device *);

         int (*resume)(struct platform_device *);

         struct device_driver driver;

};

int platform_driver_register(struct platform_driver *drv)

{

//指定了device_driver所属的总线

drv->driver.bus = &platform_bus_type;

//如果指定了platform的各项接口操作就会赋给对应的driver的接口。

if (drv->probe)

           drv->driver.probe = platform_drv_probe;

if (drv->remove)

           drv->driver.remove = platform_drv_remove;

if (drv->shutdown)

           drv->driver.shutdown = platform_drv_shutdown;

if (drv->suspend)

           drv->driver.suspend = platform_drv_suspend;

if (drv->resume)

           drv->driver.resume = platform_drv_resume;

//调用driver_register注册驱动

return driver_register(&drv->driver);

}

 

 

         这样在platform_bus_type总线上面既有设备又有驱动了。这两个注册函数是内核提供的，对于其中调用的device_register以及driver_register函数将会在后面的文章中具体介绍。在上面对pdev->dev.parent = &platform_bus;的解释中，我们得知platform_bus也是一个设备，具体将在下一篇文章里介绍。