Linux设备模型---总线、设备、驱动、设备类的相关操作

Linux设备模型---总线、设备、驱动、设备类的相关操作
2011年09月29日
　　总线相关的操作
　　注册 int bus_register(struct bus_type *bus) { int retval; struct subsys_private *priv; priv = kzalloc(sizeof(struct subsys_private), GFP_KERNEL); if (!priv) return -ENOMEM; priv->bus = bus; bus->p = priv; BLOCKING_INIT_NOTIFIER_HEAD(&priv->bus_notifier); retval = kobject_set_name(&priv->subsys.kobj, "%s", bus->name); if (retval) goto out; priv->subsys.kobj.kset = bus_kset; priv->subsys.kobj.ktype = &bus_ktype; priv->drivers_autoprobe = 1; retval = kset_register(&priv->subsys); if (retval) goto out; retval = bus_create_file(bus, &bus_attr_uevent); if (retval) goto bus_uevent_fail; priv->devices_kset = kset_create_and_add("devices", NULL, &priv->subsys.kobj); if (!priv->devices_kset) { retval = -ENOMEM; goto bus_devices_fail; } priv->drivers_kset = kset_create_and_add("drivers", NULL, &priv->subsys.kobj); if (!priv->drivers_kset) { retval = -ENOMEM; goto bus_drivers_fail; } klist_init(&priv->klist_devices, klist_devices_get, klist_devices_put); klist_init(&priv->klist_drivers, NULL, NULL); retval = add_probe_files(bus); if (retval) goto bus_probe_files_fail; retval = bus_add_attrs(bus); if (retval) goto bus_attrs_fail; pr_debug("bus: '%s': registered\n", bus->name); return 0; bus_attrs_fail: remove_probe_files(bus); bus_probe_files_fail: kset_unregister(bus->p->drivers_kset); bus_drivers_fail: kset_unregister(bus->p->devices_kset); bus_devices_fail: bus_remove_file(bus, &bus_attr_uevent); bus_uevent_fail: kset_unregister(&bus->p->subsys); out: kfree(bus->p); bus->p = NULL; return retval; } EXPORT_SYMBOL_GPL(bus_register); 
　　此函数包括如下几项工作：
　　1、首先会动态创建一个subsys_private结构体priv，并且设置priv与bus之间的映射关系。然后会阻塞notifier。紧接着会初始化priv->subsys.kobj，其中包括设置名称、其属于bus_kset以及类型为bus_ktype，接着就会注册此kset（关于kset_register参见前文)。紧接着会在sysfs文件系统中创建响应的目录以及文件。
　　2、接下来，就会创建两个kset，一个用于组织本总线上的设备对应的kobject，另一个用于组织本总线上的驱动对应的kobject。如果成功，就会创建两个klist用于组织设备和驱动的相关信息。
　　3、最后，就是根据默认属性在sysfs文件系统中创建相关的文件。
　　注销 void bus_unregister(struct bus_type *bus) { pr_debug("bus: '%s': unregistering\n", bus->name); bus_remove_attrs(bus); remove_probe_files(bus); kset_unregister(bus->p->drivers_kset); kset_unregister(bus->p->devices_kset); bus_remove_file(bus, &bus_attr_uevent); kset_unregister(&bus->p->subsys); kfree(bus->p); bus->p = NULL; } 
　　和注册完全相反的过程。
　　驱动
　　注册 int driver_register(struct device_driver *drv) { int ret; struct device_driver *other; BUG_ON(!drv->bus->p); 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); other = driver_find(drv->name, drv->bus); if (other) { put_driver(other); printk(KERN_ERR "Error: Driver '%s' is already registered, " "aborting...\n", drv->name); return -EBUSY; } ret = bus_add_driver(drv); if (ret) return ret; ret = driver_add_groups(drv, drv->groups); if (ret) bus_remove_driver(drv); return ret; } EXPORT_SYMBOL_GPL(driver_register); 
　　其实这个函数绝大部分工作都推到了函数bus_add_driver中（添加设备也是这种做法），在调用这个函数前只是简单的验证了一下该驱动是否已经注册过了。 int bus_add_driver(struct device_driver *drv) { struct bus_type *bus; struct driver_private *priv; int error = 0; 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); priv->driver = drv; drv->p = priv; priv->kobj.kset = bus->p->drivers_kset; error = kobject_init_and_add(&priv->kobj, &driver_ktype, NULL, "%s", drv->name); if (error) goto out_unregister; if (drv->bus->p->drivers_autoprobe) { error = driver_attach(drv); if (error) goto out_unregister; } klist_add_tail(&priv->knode_bus, &bus->p->klist_drivers); module_add_driver(drv->owner, drv); error = driver_create_file(drv, &driver_attr_uevent); if (error) { printk(KERN_ERR "%s: uevent attr (%s) failed\n", __func__, drv->name); } 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); } if (!drv->suppress_bind_attrs) { 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: kobject_put(&priv->kobj); kfree(drv->p); drv->p = NULL; out_put_bus: bus_put(bus); return error; } 
　　这个函数在为驱动的私有数据分配了存储空间后，就会设置驱动模型中的核心结构，包括父节点、所属kset，以及初始化私有数据内嵌的kobject等。同时会将自己加入到所属总线的所有驱动构成的链表之中。
　　紧接着就会做sysfs相关的操作，包括创建对应的目录，属性文件等，同时会想用户空间发送uevent事件。
　　注销
　　和注册相反的过程
　　设备
　　注册 int device_register(struct device *dev) { device_initialize(dev); return device_add(dev); } void device_initialize(struct device *dev) { dev->kobj.kset = devices_kset; kobject_init(&dev->kobj, &device_ktype); INIT_LIST_HEAD(&dev->dma_pools); mutex_init(&dev->mutex); lockdep_set_novalidate_class(&dev->mutex); spin_lock_init(&dev->devres_lock); INIT_LIST_HEAD(&dev->devres_head); device_pm_init(dev); set_dev_node(dev, -1); } int device_add(struct device *dev) { struct device *parent = NULL; struct class_interface *class_intf; int error = -EINVAL; dev = get_device(dev); if (!dev) goto done; if (!dev->p) { error = device_private_init(dev); if (error) goto done; } /* * for statically allocated devices, which should all be converted * some day, we need to initialize the name. We prevent reading back * the name, and force the use of dev_name() */ if (dev->init_name) { dev_set_name(dev, "%s", dev->init_name); dev->init_name = NULL; } if (!dev_name(dev)) { error = -EINVAL; goto name_error; } pr_debug("device: '%s': %s\n", dev_name(dev), __func__); parent = get_device(dev->parent); setup_parent(dev, parent); /* use parent numa_node */ if (parent) set_dev_node(dev, dev_to_node(parent)); /* first, register with generic layer. */ /* we require the name to be set before, and pass NULL */ error = kobject_add(&dev->kobj, dev->kobj.parent, NULL); if (error) goto Error; /* notify platform of device entry */ if (platform_notify) platform_notify(dev); error = device_create_file(dev, &uevent_attr); if (error) goto attrError; if (MAJOR(dev->devt)) { error = device_create_file(dev, &devt_attr); if (error) goto ueventattrError; error = device_create_sys_dev_entry(dev); if (error) goto devtattrError; devtmpfs_create_node(dev); } error = device_add_class_symlinks(dev); if (error) goto SymlinkError; error = device_add_attrs(dev); if (error) goto AttrsError; error = bus_add_device(dev); if (error) goto BusError; error = dpm_sysfs_add(dev); if (error) goto DPMError; device_pm_add(dev); /* Notify clients of device addition. This call must come * after dpm_sysf_add() and before kobject_uevent(). */ if (dev->bus) blocking_notifier_call_chain(&dev->bus->p->bus_notifi er, BUS_NOTIFY_ADD_DEVICE, dev); kobject_uevent(&dev->kobj, KOBJ_ADD); bus_probe_device(dev); if (parent) klist_add_tail(&dev->p->knode_parent, &parent->p->klist_children); if (dev->class) { mutex_lock(&dev->class->p->class_mutex); /* tie the class to the device */ klist_add_tail(&dev->knode_class, &dev->class->p->klist_devices); /* notify any interfaces that the device is here */ list_for_each_entry(class_intf, &dev->class->p->class_interfaces, node) if (class_intf->add_dev) class_intf->add_dev(dev, class_intf); mutex_unlock(&dev->class->p->class_mutex); } done: put_device(dev); return error; DPMError: bus_remove_device(dev); BusError: device_remove_attrs(dev); AttrsError: device_remove_class_symlinks(dev); SymlinkError: if (MAJOR(dev->devt)) devtmpfs_delete_node(dev); if (MAJOR(dev->devt)) device_remove_sys_dev_entry(dev); devtattrError: if (MAJOR(dev->devt)) device_remove_file(dev, &devt_attr); ueventattrError: device_remove_file(dev, &uevent_attr); attrError: kobject_uevent(&dev->kobj, KOBJ_REMOVE); kobject_del(&dev->kobj); Error: cleanup_device_parent(dev); if (parent) put_device(parent); name_error: kfree(dev->p); dev->p = NULL; goto done; } 
　　1、首先初始化dev内嵌的kobject结构体，同时对内部的各种链表、互斥量惊醒初始化。
　　2、然后就会添加设备。首先会初始化设备私有数据device_private。然后会更新其名称（按照注释，以后所有的设备结构都会动态创建，不会有静态数据）。然后会在sysfs文件系统中创建相应的目录、文件。 int bus_add_device(struct device *dev) { struct bus_type *bus = bus_get(dev->bus); int error = 0; if (bus) { pr_debug("bus: '%s': add device %s\n", bus->name, dev_name(dev)); error = device_add_attrs(bus, dev); if (error) goto out_put; error = sysfs_create_link(&bus->p->devices_kset->kobj, &dev->kobj, dev_name(dev)); if (error) goto out_id; error = sysfs_create_link(&dev->kobj, &dev->bus->p->subsys.kobj, "subsystem"); if (error) goto out_subsys; klist_add_tail(&dev->p->knode_bus, &bus->p->klist_devices); } return 0; out_subsys: sysfs_remove_link(&bus->p->devices_kset->kobj, dev_name(dev)); out_id: device_remove_attrs(bus, dev); out_put: bus_put(dev->bus); return error; } 
　　3、紧接着会调用bus_add_device、bus_probe_device进行总线、设备、驱动三者之间的匹配、设置。
　　4、最后一步就是向用户空间发送uevent事件，设置设备类的关系。
　　注销
　　和注册相反的过程