kobject

/*
 * kobject.h - generic kernel object infrastructure.
 *
 * Copyright (c) 2002-2003    Patrick Mochel
 * Copyright (c) 2002-2003    Open Source Development Labs
 *
 * This file is released under the GPLv2.
 *
 *
 * Please read Documentation/kobject.txt before using the kobject
 * interface, ESPECIALLY the parts about reference counts and object
 * destructors.
 */

#ifndef _KOBJECT_H_
#define _KOBJECT_H_

#ifdef __KERNEL__

#include <linux/types.h>
#include <linux/list.h>
#include <linux/sysfs.h>
#include <linux/compiler.h>
#include <linux/spinlock.h>
#include <linux/kref.h>
#include <linux/kernel.h>
#include <linux/wait.h>
#include <asm/atomic.h>

#define KOBJ_NAME_LEN            20
#define UEVENT_HELPER_PATH_LEN        256

/* path to the userspace helper executed on an event */
extern char uevent_helper[];

/* counter to tag the uevent, read only except for the kobject core */
extern u64 uevent_seqnum;

/* the actions here must match the proper string in lib/kobject_uevent.c */
typedef int __bitwise kobject_action_t;
enum kobject_action {
    KOBJ_ADD    = (__force kobject_action_t) 0x01,    /* exclusive to core */
    KOBJ_REMOVE    = (__force kobject_action_t) 0x02,    /* exclusive to core */
    KOBJ_CHANGE    = (__force kobject_action_t) 0x03,    /* device state change */
    KOBJ_OFFLINE    = (__force kobject_action_t) 0x04,    /* device offline */
    KOBJ_ONLINE    = (__force kobject_action_t) 0x05,    /* device online */
    KOBJ_MOVE    = (__force kobject_action_t) 0x06,    /* device move */                                        
};

struct kobject {
//如果名称长度小于KOBJ_NAME_LEN（20）字节，则kobject的名称便存放到
//name数组中，k_name指向数组头，如果大于，则动态分配一个足够大的
//缓冲区来存放kobject的名称，这是k_name指向缓冲区。  
    const char        * k_name;    //指向kobject名称的起始位置  
    
/*kobject 的名字数组(sysfs入口使用的名字)，若名字数组大小不小于KOBJ_NAME_LEN，只储存前KOBJ_NAME_LEN个字符*/
    char            name[KOBJ_NAME_LEN];    //对象名称        
    struct kref        //kref;    /*引用计数*/
    
    struct list_head    entry;    /*kobject 之间的双向链表，与所属的kset形成环形链表*/
    
//指向kobject的父对象，以此来在内核中构造一个对象层次结构，并且
//可以将多个对象之间的关系表现出来，这就是sysfs的真相：一个
//用户空间的文件系统，用来表示内核中kobject对象的层次结构。
/*在sysfs分层结构中定位对象，指向上一级kset中的struct kobject kobj*/
    struct kobject        * parent;

    struct kset        * kset;    /*指向所属的kset*/      
    struct kobj_type    * ktype;        //指向对象类型描述符指针

//sysfs文件系统中与该对象对应的文件节点入口
//目录项，在sysfs中该结构体就表示这个kobject
    struct dentry        * dentry;。
    wait_queue_head_t    poll;    /*等待队列头*/
};

extern int kobject_set_name(struct kobject *, const char *, ...)
    __attribute__((format(printf,2,3)));

static inline const char * kobject_name(const struct kobject * kobj)
{
    return kobj->k_name;
}

extern void kobject_init(struct kobject *);
extern void kobject_cleanup(struct kobject *);

extern int __must_check kobject_add(struct kobject *);
extern int __must_check kobject_shadow_add(struct kobject *, struct dentry *);
extern void kobject_del(struct kobject *);

extern int __must_check kobject_rename(struct kobject *, const char *new_name);
extern int __must_check kobject_shadow_rename(struct kobject *kobj,
                        struct dentry *new_parent,
                        const char *new_name);
extern int __must_check kobject_move(struct kobject *, struct kobject *);

extern int __must_check kobject_register(struct kobject *);
extern void kobject_unregister(struct kobject *);

extern struct kobject * kobject_get(struct kobject *);
extern void kobject_put(struct kobject *);

extern struct kobject *kobject_kset_add_dir(struct kset *kset,
                        struct kobject *, const char *);
extern struct kobject *kobject_add_dir(struct kobject *, const char *);

extern char * kobject_get_path(struct kobject *, gfp_t);

struct kobj_type {
    void (*release)(struct kobject *);    //提供kobject结构的析构函数
    struct sysfs_ops    * sysfs_ops;    //属性操作,对应于sysfs操作
    struct attribute    ** default_attrs;    //默认属性
};


/**
 *    kset - a set of kobjects of a specific type, belonging
 *    to a specific subsystem.
 *
 *    All kobjects of a kset should be embedded in an identical
 *    type. This type may have a descriptor, which the kset points
 *    to. This allows there to exist sets of objects of the same
 *    type in different subsystems.
 *
 *    A subsystem does not have to be a list of only one type
 *    of object; multiple ksets can belong to one subsystem. All
 *    ksets of a subsystem share the subsystem's lock.
 *
 *    Each kset can support specific event variables; it can
 *    supress the event generation or add subsystem specific
 *    variables carried with the event.
 */
struct kset_uevent_ops {
    int (*filter)(struct kset *kset, struct kobject *kobj);        //事件过滤
    const char *(*name)(struct kset *kset, struct kobject *kobj);
    int (*uevent)(struct kset *kset, struct kobject *kobj, char **envp,
            int num_envp, char *buffer, int buffer_size);    //环境变量设置
};

struct kset {
    struct kobj_type    * ktype;    /*指向该kset对象类型描述符的指针*/
    struct list_head    list;    /*用于连接该kset中所有kobject以形成环形链表的链表头*/
    spinlock_t        list_lock;    /*当遍历list时，使用的锁,用于避免竞态*/
    struct kobject        kobj;    /*嵌入的kobject,    居然递归嵌套，我晕。。。。*/
/*原有的struct kset_hotplug_ops * hotplug_ops;已经不存在，被kset_uevent_ops 结构体替换
用于热插拔操作*/
//uevent相关操作函数，如果kset中的kobject发生事件，调用之
    struct kset_uevent_ops    * uevent_ops;
};

extern void kset_init(struct kset * k);    
extern int __must_check kset_add(struct kset * k);
extern int __must_check kset_register(struct kset * k);
extern void kset_unregister(struct kset * k);

static inline struct kset * to_kset(struct kobject * kobj)
{
    return kobj ? container_of(kobj,struct kset,kobj) : NULL;
}

static inline struct kset * kset_get(struct kset * k)
{
    return k ? to_kset(kobject_get(&k->kobj)) : NULL;
}

static inline void kset_put(struct kset * k)
{
    kobject_put(&k->kobj);
}

static inline struct kobj_type * get_ktype(struct kobject * k)
{
    if (k->kset && k->kset->ktype)
        return k->kset->ktype;
    else
        return k->ktype;
}

extern struct kobject * kset_find_obj(struct kset *, const char *);


/**
 * Use this when initializing an embedded kset with no other
 * fields to initialize.
 */
#define set_kset_name(str)    .kset = { .kobj = { .name = str } }


#define decl_subsys(_name,_type,_uevent_ops) \
struct kset _name##_subsys = { \
    .kobj = { .name = __stringify(_name) }, \
    .ktype = _type, \
    .uevent_ops =_uevent_ops, \
}
#define decl_subsys_name(_varname,_name,_type,_uevent_ops) \
struct kset _varname##_subsys = { \
    .kobj = { .name = __stringify(_name) }, \
    .ktype = _type, \
    .uevent_ops =_uevent_ops, \
}

/* The global /sys/kernel/ subsystem for people to chain off of */
extern struct kset kernel_subsys;
/* The global /sys/hypervisor/ subsystem  */
extern struct kset hypervisor_subsys;

/**
 * Helpers for setting the kset of registered objects.
 * Often, a registered object belongs to a kset embedded in a
 * subsystem. These do no magic, just make the resulting code
 * easier to follow.
 */

/**
 *    kobj_set_kset_s(obj,subsys) - set kset for embedded kobject.
 *    @obj:        ptr to some object type.
 *    @subsys:    a subsystem object (not a ptr).
 *
 *    Can be used for any object type with an embedded ->kobj.
 */

#define kobj_set_kset_s(obj,subsys) \
    (obj)->kobj.kset = &(subsys)

/**
 *    kset_set_kset_s(obj,subsys) - set kset for embedded kset.
 *    @obj:        ptr to some object type.
 *    @subsys:    a subsystem object (not a ptr).
 *
 *    Can be used for any object type with an embedded ->kset.
 *    Sets the kset of @obj's  embedded kobject (via its embedded
 *    kset) to @subsys.kset. This makes @obj a member of that
 *    kset.
 */

#define kset_set_kset_s(obj,subsys) \
    (obj)->kset.kobj.kset = &(subsys)

/**
 *    subsys_set_kset(obj,subsys) - set kset for subsystem
 *    @obj:        ptr to some object type.
 *    @subsys:    a subsystem object (not a ptr).
 *
 *    Can be used for any object type with an embedded ->subsys.
 *    Sets the kset of @obj's kobject to @subsys.kset. This makes
 *    the object a member of that kset.
 */

#define subsys_set_kset(obj,_subsys) \
    (obj)->subsys.kobj.kset = &(_subsys)

extern void subsystem_init(struct kset *);
extern int __must_check subsystem_register(struct kset *);
extern void subsystem_unregister(struct kset *);

static inline struct kset *subsys_get(struct kset *s)
{
    if (s)
        return kset_get(s);
    return NULL;
}

static inline void subsys_put(struct kset *s)
{
    kset_put(s);
}

struct subsys_attribute {
    struct attribute attr;
    ssize_t (*show)(struct kset *, char *);
    ssize_t (*store)(struct kset *, const char *, size_t);
};

extern int __must_check subsys_create_file(struct kset *,
                    struct subsys_attribute *);

#if defined(CONFIG_HOTPLUG)
int kobject_uevent(struct kobject *kobj, enum kobject_action action);
int kobject_uevent_env(struct kobject *kobj, enum kobject_action action,
            char *envp[]);

int add_uevent_var(char **envp, int num_envp, int *cur_index,
            char *buffer, int buffer_size, int *cur_len,
            const char *format, ...)
    __attribute__((format (printf, 7, 8)));
#else
static inline int kobject_uevent(struct kobject *kobj, enum kobject_action action)
{ return 0; }
static inline int kobject_uevent_env(struct kobject *kobj,
                      enum kobject_action action,
                      char *envp[])
{ return 0; }

static inline int add_uevent_var(char **envp, int num_envp, int *cur_index,
                      char *buffer, int buffer_size, int *cur_len,
                      const char *format, ...)
{ return 0; }
#endif

#endif /* __KERNEL__ */
#endif /* _KOBJECT_H_ */