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#include <linux/kobject.h>
struct kobject {
	const char		*name;
	struct list_head	entry;
	struct kobject		*parent; // 指向父对象的指针
	struct kset		*kset;	 // 所属于哪个kset
	struct kobj_type	*ktype; // 对象类型描述符指针
	struct sysfs_dirent	*sd;
	struct kref		kref; // 对象引用计数
	unsigned int state_initialized:1;
	unsigned int state_in_sysfs:1;
	unsigned int state_add_uevent_sent:1;
	unsigned int state_remove_uevent_sent:1;
	unsigned int uevent_suppress:1;
};

struct kobj_type { 
    void (*release)(struct kobject *); /*当kobject的引用计数为0时调用此函数，用以释放资源*/
	const struct sysfs_ops *sysfs_ops;
	struct attribute	**default_attrs; 
}; 

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void kobject_init(struct kobject *kobj, struct kobj_type *ktype);
		/*初始化kobject, 设置引用计数为1， entry域指向自己，其所属的kset引用计数加1*/
int kobject_set_name(struct kobject *kobj, const char *name, ...);
		/*用于设置kobject的名字*/

int kobject_add(struct kobject *kobj, struct kobject *parent, const char *fmt, ...);
		/*该函数用于将kobject对象加入Linux设备层次，它会挂接该kobject对象到kset的list链中，增加父目录各级kobject的引用计数，在其parent指向的目录下创建文件节点，并启动该类型内核对象的hotplug函数*/
void kobject_del(struct kobject *kobj);
		/*该函数执行和kobject_add()相反的操作*/

void kobject_cleanup(struct kobject *kobj);
void kobject_release(struct kref *kref)
		/*这两个函数用于清除kobject，当其引用计数为0时，释放对象所占用的资源*/
struct kobject *kobject_get(struct kobject *kobj);
void kobject_put(struct kobject *kobj);
		/*这两个函数分配用于增加和减少引用计数，当引用计数为0时，所有该对象使用的资源将被释放*/

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#include <linux/kobject.h>
struct kset {
	struct list_head list;
	spinlock_t list_lock;
	struct kobject kobj; /* 内嵌一个kobject对象，用作kset的引用计数，也作为集合内所有kobject对象的parent*/
	const struct kset_uevent_ops *uevent_ops;
};

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void kset_init(struct kset *kset);
int __must_check kset_register(struct kset *kset);
void kset_unregister(struct kset *kset);
struct kset *kset_get(struct kset *k);
void kset_put(struct kset *k);

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struct kset_uevent_ops {
	int (* const filter)(struct kset *kset, struct kobject *kobj);//用与过滤掉不需要导出的事件
	const char *(* const name)(struct kset *kset, struct kobject *kobj);//用于导出一些环境变量给用户空间的热插拔处理程序。用户空间的热插拔脚本根据传入的参数，以及内核导出便来给你采取行动。
	int (* const uevent)(struct kset *kset, struct kobject *kobj,
		      struct kobj_uevent_env *env);
};

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#include <linux/device.h>
/**
 * struct device - The basic device structure
 * @parent:	The device's "parent" device, the device to which it is attached.
 * 		In most cases, a parent device is some sort of bus or host
 * 		controller. If parent is NULL, the device, is a top-level device,
 * 		which is not usually what you want.
 * @p:		Holds the private data of the driver core portions of the device.
 * 		See the comment of the struct device_private for detail.
 * @kobj:	A top-level, abstract class from which other classes are derived.
 * @init_name:	Initial name of the device.
 * @type:	The type of device.
 * 		This identifies the device type and carries type-specific
 * 		information.
 * @mutex:	Mutex to synchronize calls to its driver.
 * @bus:	Type of bus device is on.
 * @driver:	Which driver has allocated this
 * @platform_data: Platform data specific to the device.
 * 		Example: For devices on custom boards, as typical of embedded
 * 		and SOC based hardware, Linux often uses platform_data to point
 * 		to board-specific structures describing devices and how they
 * 		are wired.  That can include what ports are available, chip
 * 		variants, which GPIO pins act in what additional roles, and so
 * 		on.  This shrinks the "Board Support Packages" (BSPs) and
 * 		minimizes board-specific #ifdefs in drivers.
 * @power:	For device power management.
 * 		See Documentation/power/devices.txt for details.
 * @pwr_domain:	Provide callbacks that are executed during system suspend,
 * 		hibernation, system resume and during runtime PM transitions
 * 		along with subsystem-level and driver-level callbacks.
 * @numa_node:	NUMA node this device is close to.
 * @dma_mask:	Dma mask (if dma'ble device).
 * @coherent_dma_mask: Like dma_mask, but for alloc_coherent mapping as not all
 * 		hardware supports 64-bit addresses for consistent allocations
 * 		such descriptors.
 * @dma_parms:	A low level driver may set these to teach IOMMU code about
 * 		segment limitations.
 * @dma_pools:	Dma pools (if dma'ble device).
 * @dma_mem:	Internal for coherent mem override.
 * @archdata:	For arch-specific additions.
 * @of_node:	Associated device tree node.
 * @devt:	For creating the sysfs "dev".
 * @devres_lock: Spinlock to protect the resource of the device.
 * @devres_head: The resources list of the device.
 * @knode_class: The node used to add the device to the class list.
 * @class:	The class of the device.
 * @groups:	Optional attribute groups.
 * @release:	Callback to free the device after all references have
 * 		gone away. This should be set by the allocator of the
 * 		device (i.e. the bus driver that discovered the device).
 *
 * At the lowest level, every device in a Linux system is represented by an
 * instance of struct device. The device structure contains the information
 * that the device model core needs to model the system. Most subsystems,
 * however, track additional information about the devices they host. As a
 * result, it is rare for devices to be represented by bare device structures;
 * instead, that structure, like kobject structures, is usually embedded within
 * a higher-level representation of the device.
 */
struct device {
	struct device		*parent; 

	struct device_private	*p;

	struct kobject kobj; // 内嵌一个kobject对象
	const char		*init_name; /* initial name of the device */
	const struct device_type *type;

	struct mutex		mutex;	/* mutex to synchronize calls to its driver.*/

	struct bus_type	*bus;		/* type of bus device is on */
	struct device_driver *driver;	/* which driver has allocated this device */
	void		*platform_data;	/* Platform specific data, device
					   core doesn't touch it */
	/* 省略 */

	struct device_node	*of_node; /* associated device tree node */

	dev_t			devt;	/* dev_t, creates the sysfs "dev" */

	spinlock_t		devres_lock;
	struct list_head	devres_head;

	struct klist_node	knode_class;
	struct class		*class;
	const struct attribute_group **groups;	
	
	void	(*release)(struct device *dev);
};

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int __must_check device_register(struct device *dev); //此函数调用device_add()函数，将一个新的device对象插入设备模型，并自动在/sys/devices下创建一个对应的目录
void device_unregister(struct device *dev); //执行与device_register()函数相反的操作

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#include <linux/device.h>
/**
 * struct device_driver - The basic device driver structure
 * @name:	Name of the device driver.
 * @bus:	The bus which the device of this driver belongs to.
 * @owner:	The module owner.
 * @mod_name:	Used for built-in modules.
 * @suppress_bind_attrs: Disables bind/unbind via sysfs.
 * @of_match_table: The open firmware table.
 * @probe:	Called to query the existence of a specific device,
 *		whether this driver can work with it, and bind the driver
 *		to a specific device.
 * @remove:	Called when the device is removed from the system to
 *		unbind a device from this driver.
 * @shutdown:	Called at shut-down time to quiesce the device.
 * @suspend:	Called to put the device to sleep mode. Usually to a
 *		low power state.
 * @resume:	Called to bring a device from sleep mode.
 * @groups:	Default attributes that get created by the driver core
 *		automatically.
 * @pm:		Power management operations of the device which matched
 *		this driver.
 * @p:		Driver core's private data, no one other than the driver
 *		core can touch this.
 *
 * The device driver-model tracks all of the drivers known to the system.
 * The main reason for this tracking is to enable the driver core to match
 * up drivers with new devices. Once drivers are known objects within the
 * system, however, a number of other things become possible. Device drivers
 * can export information and configuration variables that are independent
 * of any specific device.
 */
struct device_driver {
	const char		*name;
	struct bus_type		*bus;

	struct module		*owner;
	const char		*mod_name;	/* used for built-in modules */

	bool suppress_bind_attrs;	/* disables bind/unbind via sysfs */

	const struct of_device_id	*of_match_table;

	int (*probe) (struct device *dev);
	int (*remove) (struct device *dev);
	void (*shutdown) (struct device *dev);
	int (*suspend) (struct device *dev, pm_message_t state);
	int (*resume) (struct device *dev);
	const struct attribute_group **groups;

	const struct dev_pm_ops *pm;

	struct driver_private *p;
};

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int __must_check driver_register(struct device_driver *drv);
void driver_unregister(struct device_driver *drv);

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#include <linux/device.h>
/**
 * struct bus_type - The bus type of the device
 *
 * @name:	The name of the bus.
 * @bus_attrs:	Default attributes of the bus.
 * @dev_attrs:	Default attributes of the devices on the bus.
 * @drv_attrs:	Default attributes of the device drivers on the bus.
 * @match:	Called, perhaps multiple times, whenever a new device or driver
 *		is added for this bus. It should return a nonzero value if the
 *		given device can be handled by the given driver.
 * @uevent:	Called when a device is added, removed, or a few other things
 *		that generate uevents to add the environment variables.
 * @probe:	Called when a new device or driver add to this bus, and callback
 *		the specific driver's probe to initial the matched device.
 * @remove:	Called when a device removed from this bus.
 * @shutdown:	Called at shut-down time to quiesce the device.
 * @suspend:	Called when a device on this bus wants to go to sleep mode.
 * @resume:	Called to bring a device on this bus out of sleep mode.
 * @pm:		Power management operations of this bus, callback the specific
 *		device driver's pm-ops.
 * @p:		The private data of the driver core, only the driver core can
 *		touch this.
 *
 * A bus is a channel between the processor and one or more devices. For the
 * purposes of the device model, all devices are connected via a bus, even if
 * it is an internal, virtual, "platform" bus. Buses can plug into each other.
 * A USB controller is usually a PCI device, for example. The device model
 * represents the actual connections between buses and the devices they control.
 * A bus is represented by the bus_type structure. It contains the name, the
 * default attributes, the bus' methods, PM operations, and the driver core's
 * private data.
 */

struct bus_type {
	const char		*name;
	struct bus_attribute	*bus_attrs;
	struct device_attribute	*dev_attrs;
	struct driver_attribute	*drv_attrs;

	int (*match)(struct device *dev, struct device_driver *drv);
	int (*uevent)(struct device *dev, struct kobj_uevent_env *env);
	int (*probe)(struct device *dev);
	int (*remove)(struct device *dev);
	void (*shutdown)(struct device *dev);

	int (*suspend)(struct device *dev, pm_message_t state);
	int (*resume)(struct device *dev);

	const struct dev_pm_ops *pm;

	struct subsys_private *p;
};

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int __must_check bus_register(struct bus_type *bus);
void bus_unregister(struct bus_type *bus);

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#include <linux/device.h>
/**
 * struct class - device classes
 * @name:	Name of the class.
 * @owner:	The module owner.
 * @class_attrs: Default attributes of this class.
 * @dev_attrs:	Default attributes of the devices belong to the class.
 * @dev_bin_attrs: Default binary attributes of the devices belong to the class.
 * @dev_kobj:	The kobject that represents this class and links it into the hierarchy.
 * @dev_uevent:	Called when a device is added, removed from this class, or a
 *		few other things that generate uevents to add the environment
 *		variables.
 * @devnode:	Callback to provide the devtmpfs.
 * @class_release: Called to release this class.
 * @dev_release: Called to release the device.
 * @suspend:	Used to put the device to sleep mode, usually to a low power
 *		state.
 * @resume:	Used to bring the device from the sleep mode.
 * @ns_type:	Callbacks so sysfs can detemine namespaces.
 * @namespace:	Namespace of the device belongs to this class.
 * @pm:		The default device power management operations of this class.
 * @p:		The private data of the driver core, no one other than the
 *		driver core can touch this.
 *
 * A class is a higher-level view of a device that abstracts out low-level
 * implementation details. Drivers may see a SCSI disk or an ATA disk, but,
 * at the class level, they are all simply disks. Classes allow user space
 * to work with devices based on what they do, rather than how they are
 * connected or how they work.
 */
struct class {
	const char		*name;
	struct module		*owner;

	struct class_attribute		*class_attrs;
	struct device_attribute		*dev_attrs;
	struct bin_attribute		*dev_bin_attrs;
	struct kobject			*dev_kobj;

	int (*dev_uevent)(struct device *dev, struct kobj_uevent_env *env);
	char *(*devnode)(struct device *dev, mode_t *mode);

	void (*class_release)(struct class *class);
	void (*dev_release)(struct device *dev);

	int (*suspend)(struct device *dev, pm_message_t state);
	int (*resume)(struct device *dev);

	const struct kobj_ns_type_operations *ns_type;
	const void *(*namespace)(struct device *dev);

	const struct dev_pm_ops *pm;

	struct subsys_private *p;
};

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struct bus_attribute {
	struct attribute	attr;
	ssize_t (*show)(struct bus_type *bus, char *buf);
	ssize_t (*store)(struct bus_type *bus, const char *buf, size_t count);
};

#define BUS_ATTR(_name, _mode, _show, _store)	\
struct bus_attribute bus_attr_##_name = __ATTR(_name, _mode, _show, _store) //创建初始化宏

int __must_check bus_create_file(struct bus_type *, struct bus_attribute *);
void bus_remove_file(struct bus_type *, struct bus_attribute *);
// xxx_create_file()函数会调用sysfs_create_file()函数创建对应的sys文件节点
// xxx_remove_file()函数会调用sysfs_remove_file()函数删除对应的sys文件节点