关于platform_driver 是如何匹配 platform_device的和如何调用到platform_driver中的probe函数的研究

        在linux中platform平台驱动又三大部分组成，第一是bus、第二是驱动、第三是设备。

      第一总线也就是platform_bus，总线也是一种特殊的device，到底层下面还是要调用device_register来注册该总线设备，然后是用来注册总线的属性结构体 bus_type（platform_bus_type），至此platform平台的总线已经准备好。具体介绍可以看我另一篇博客。

      第二是设备，platform_device，它的注册流程是：platform_device_register(struct platform_device *pdev)->device_initialize(&pdev->dev)->platform_device_add(pdev)->pdev->dev.bus = &platform_bus_type->device_add(&pdev->dev)->把设备挂在虚拟的platform bus下。

       第三是驱动，现在总线、设备都准备好了，然后等着驱动来匹配设备进行驱动，具体的驱动匹配设备流程如下：

 1、

int platform_driver_register(struct platform_driver *drv){drv->driver.bus = &platform_bus_type;//驱动的总线类型指向platform_bus_typeif (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;return driver_register(&drv->driver);}

 2、

int driver_register(struct device_driver *drv){int ret;struct device_driver *other;BUG_ON(!drv->bus->p);//检测总线的操作函数和驱动的操作函数是否同时存在,同时存在则提示使用总线提供的操作函数if ((drv->bus->probe && drv->probe) ||    (drv->bus->remove && drv->remove) ||    (drv->bus->shutdown && drv->shutdown))printk(KERN_WARNING "Driver '%s' needs updating - please use ""bus_type methods\n", drv->name);//查找这个驱动是否已经在总线上注册，并增加引用计数，若已经注册，则返回提示信息。other = driver_find(drv->name, drv->bus);if (other) {//如果已经被注册，则返回提示错误并且减少引用计数。put_driver(other);printk(KERN_ERR "Error: Driver '%s' is already registered, ""aborting...\n", drv->name);return -EEXIST;}//若还没有注册，则在总线上注册该驱动ret = bus_add_driver(drv);if (ret)return ret;ret = driver_add_groups(drv, drv->groups);if (ret)bus_remove_driver(drv);return ret;}

3、

 

int bus_add_driver(struct device_driver *drv){struct bus_type *bus;struct driver_private *priv;int error = 0;//用于增加该bus所属的顶层bus的kobject的引用计数，返回的是其所属的顶层bus的指针。bus = bus_get(drv->bus);if (!bus)return -EINVAL;pr_debug("bus: '%s': add driver %s\n", bus->name, drv->name);priv = kzalloc(sizeof(*priv), GFP_KERNEL);if (!priv) {error = -ENOMEM;goto out_put_bus;}klist_init(&priv->klist_devices, NULL, NULL);//将这两个结构体连接起来priv->driver = drv;drv->p = priv;//指向顶层的bus的p->drivers_kset//设置私有数据的父容器,在这一步中,设置了kset为platform下的drivers_kset结构,也就是drivers呢个目录 priv->kobj.kset = bus->p->drivers_kset;//初始化kobj对象,设置容器操作集并建立相应的目录,这里由于没有提供parent,所以会使用父容器中的kobj为父对象  error = kobject_init_and_add(&priv->kobj, &driver_ktype, NULL,     "%s", drv->name);if (error)goto out_unregister;//检测所属总线的drivers_autoprobe属性是否为真     //为真则进行与设备的匹配,到这里,就会与我们之前注册的test_device连接上了,  //至于如何连接,进行了什么操作,将在别的文章中详细描述 if (drv->bus->p->drivers_autoprobe) {error = driver_attach(drv);if (error)goto out_unregister;}//挂载到所属总线驱动链表上klist_add_tail(&priv->knode_bus, &bus->p->klist_drivers);module_add_driver(drv->owner, drv);//建立uevent属性文件error = driver_create_file(drv, &driver_attr_uevent);if (error) {printk(KERN_ERR "%s: uevent attr (%s) failed\n",__func__, drv->name);}//建立设备属性文件error = driver_add_attrs(bus, drv);if (error) {/* How the hell do we get out of this pickle? Give up */printk(KERN_ERR "%s: driver_add_attrs(%s) failed\n",__func__, drv->name);}error = add_bind_files(drv);if (error) {/* Ditto */printk(KERN_ERR "%s: add_bind_files(%s) failed\n",__func__, drv->name);}kobject_uevent(&priv->kobj, KOBJ_ADD);return 0;out_unregister:kfree(drv->p);drv->p = NULL;kobject_put(&priv->kobj);out_put_bus:bus_put(bus);return error;}

 4、驱动的匹配关键是上面函数中的

if (drv->bus->p->drivers_autoprobe) {//drivers_autoprobe在初始化的时候定义为1，系统则会调用下面的driver_attach函数进行驱动与设备的匹配error = driver_attach(drv);if (error)goto out_unregister;}

 

int driver_attach(struct device_driver *drv){return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);}

 //bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);int bus_for_each_dev(struct bus_type *bus, struct device *start,     void *data, int (*fn)(struct device *, void *)){/*struct klist_iter {struct klist*i_klist;struct klist_node*i_cur;};*/struct klist_iter i;struct device *dev;int error = 0;if (!bus)return -EINVAL;//如果第三个参数不为空就增加引用计数klist_iter_init_node(&bus->p->klist_devices, &i,     (start ? &start->p->knode_bus : NULL));//一直是NULL//经过上面的宏之后，i实际上变成了i->i_klist=&bus->p->klist_devices,bus->p->klist_devices指向的是挂接在它上面的所有的设备的指针     while ((dev = next_device(&i)) && !error)//fu函数传入的是device的指针和device_driver的指针，error = fn(dev, data);//如果klist_iter_init_node第三个参数不为空则减少引用计数klist_iter_exit(&i);return error;}

 //寻找到下一个设备的节点

static struct device *next_device(struct klist_iter *i){struct klist_node *n = klist_next(i);struct device *dev = NULL;struct device_private *dev_prv;if (n) {dev_prv = to_device_private_bus(n);dev = dev_prv->device;}return dev;}

 函数error = fn(dev, data)的原型如下：

传进来的参数第一个参数为不断遍历到的设备节点的指针，第二个参数为固定的一个驱动所对应的struct device_driver *drv指针，这样就实现驱动和设备的匹配

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. *///当设备和驱动的名字不匹配的时候返回的是0，然后就会调用下面的return 0；if (!driver_match_device(drv, dev))return 0;if (dev->parent)/* Needed for USB */down(&dev->parent->sem);down(&dev->sem);if (!dev->driver)driver_probe_device(drv, dev);//调用探测函数进行探测，并且调用platform_driver中的probe函数up(&dev->sem);if (dev->parent)up(&dev->parent->sem);return 0;}

在上面有两个比较关键的函数driver_match_device(dre,dev),函数原型如下：

static inline int driver_match_device(struct device_driver *drv,      struct device *dev){return drv->bus->match ? drv->bus->match(dev, drv) : 1;//无论设备与驱动是否匹配成功都会返回1}

当驱动的指针不为空的时候，这个drv->bus所指向的的这个驱动所属的的总线的bus_type中的match函数，然后传进去的是该驱动的指针和设备的指针

static int platform_match(struct device *dev, struct device_driver *drv){struct platform_device *pdev = to_platform_device(dev);struct platform_driver *pdrv = to_platform_driver(drv);/* match against the id table first */if (pdrv->id_table)//为空，不会被调用return platform_match_id(pdrv->id_table, pdev) != NULL;/* fall-back to driver name match */return (strcmp(pdev->name, drv->name) == 0);}

最后调用驱动的probe函数进行设备的探测

driver_probe_device(drv, dev);//调用探测函数进行探测，并且调用platform_driver中的probe函数

int driver_probe_device(struct device_driver *drv, struct device *dev){int ret = 0;//再次检查设备有没有在总线上注册，当发现还没有注册的时候，返回一个错误if (!device_is_registered(dev))return -ENODEV;pr_debug("bus: '%s': %s: matched device %s with driver %s\n", drv->bus->name, __func__, dev_name(dev), drv->name);ret = really_probe(dev, drv);return ret;}

 

static int really_probe(struct device *dev, struct device_driver *drv){int ret = 0;atomic_inc(&probe_count);pr_debug("bus: '%s': %s: probing driver %s with device %s\n", drv->bus->name, __func__, drv->name, dev_name(dev));WARN_ON(!list_empty(&dev->devres_head));//找到了设备的驱动，并且将dev->driver指针指向自己的这个驱动dev->driver = drv;if (driver_sysfs_add(dev)) {//在sys目录下建立连接指向自己的在sys中的driversprintk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",__func__, dev_name(dev));goto probe_failed;}//在bus_type  platform_bus_type中并没有设置probe函数，所以下面函数并不会被调用if (dev->bus->probe) {ret = dev->bus->probe(dev);if (ret)goto probe_failed;} else if (drv->probe) {//上面总线没有probe函数，所以直接调用驱动当中的probe函数ret = drv->probe(dev);if (ret)goto probe_failed;}driver_bound(dev);ret = 1;pr_debug("bus: '%s': %s: bound device %s to driver %s\n", drv->bus->name, __func__, dev_name(dev), drv->name);goto done;probe_failed:devres_release_all(dev);driver_sysfs_remove(dev);dev->driver = NULL;if (ret != -ENODEV && ret != -ENXIO) {/* driver matched but the probe failed */printk(KERN_WARNING       "%s: probe of %s failed with error %d\n",       drv->name, dev_name(dev), ret);}/* * Ignore errors returned by ->probe so that the next driver can try * its luck. */ret = 0;done:atomic_dec(&probe_count);wake_up(&probe_waitqueue);return ret;}

        至此platform_driver的probe函数实现了调用并且匹配了platform_device