kobject.c 添加注释

2  *    populate_dir - populate directory with attributes.
3  *    @kobj:    object we're working on.
4  *
5  *    Most subsystems have a set of default attributes that
6  *    are associated with an object that registers with them.
7  *    This is a helper called during object registration that
8  *    loops through the default attributes of the subsystem
9  *    and creates attributes files for them in sysfs.
10  *
11  */
12
13 static int populate_dir(struct kobject * kobj)
14 {
15     /* [cgw]: 从kobject取出kobj_type成员指针 */
16     struct kobj_type * t = get_ktype(kobj);
17     struct attribute * attr;
18     int error = 0;
19     int i;
20     /* [cgw]: kobj_type中默认属性default_attrs不为空，即已经添加一个或以上
21       * 属性项
22       */
23     if (t && t->default_attrs) {
24         /* [cgw]: 轮询default_attrs中的指针不为空，即已经添加属性 */
25         for (i = 0; (attr = t->default_attrs[i]) != NULL; i++) {
26             /* [cgw]: 在sysfs中为这个kobj创建一个属性文件 */
27             if ((error = sysfs_create_file(kobj,attr)))
28                 break;
29         }
30     }
31     return error;
32 }

2 {
3     int error = 0;
4     /* [cgw]: 获得这个kobj的名字，名字不为空 */
5     if (kobject_name(kobj)) {
6         /* [cgw]: 为kobj创建一个目录
7               * @shadow_parent:    parent parent object. (父对象)
8               *
9               */
10         error = sysfs_create_dir(kobj, shadow_parent);
11         if (!error) {
12             /* [cgw]: 添加kobj属性*/
13             if ((error = populate_dir(kobj)))
14                 /* [cgw]: 添加失败，删除kobj对象目录 */
15                 sysfs_remove_dir(kobj);
16         }
17     }
18     return error;
19 }

2 {
3     /* [cgw]: 从链表list_head取出一个entry
4           * 根据这个entry，找到包含这个entry的
5           * kobject结构体地址
6           */
7     return container_of(entry,struct kobject,entry);
8 }

2 {
3     int length = 1;
4     struct kobject * parent = kobj;
5
6     /* walk up the ancestors until we hit the one pointing to the
7      * root.
8      * Add 1 to strlen for leading '/' of each level.
9      */
10     /* [cgw]: 逐个节点查找对象的名字，计算每节点对象的名字长度，
11       * 并加1，加1是每个名字前有个'/'，并累计所有名字长度
12       */
13     do {
14         /* [cgw]: 名字不为空 */
15         if (kobject_name(parent) == NULL)
16             return 0;
17         /* [cgw]: 累计名字长度 */
18         length += strlen(kobject_name(parent)) + 1;
19         /* [cgw]: 指向上一节点(当前对象的父辈) */
20         parent = parent->parent;
21     } while (parent);
22     return length;
23 }

2 {
3     struct kobject * parent;
4
5     /* [cgw]: 逐个节点查找对象的名字，并填装到path中 */
6     --length;
7     for (parent = kobj; parent; parent = parent->parent) {
8         /* [cgw]: 计算当前节点对象名字长度 */
9         int cur = strlen(kobject_name(parent));
10         /* back up enough to print this name with '/' */
11         /* [cgw]: 总长度减去一个名字的长度 */
12         length -= cur;
13         /* [cgw]: 把这个对象名字填装到path的path + length位置 */
14         strncpy (path + length, kobject_name(parent), cur);
15         /* [cgw]: 在path的path + length -1的位置插入'/' */
16         *(path + --length) = '/';
17     }
18
19     pr_debug("%s: path = '%s' ",__FUNCTION__,path);
20 }

2  * kobject_get_path - generate and return the path associated with a given kobj and kset pair.
3  *
4  * @kobj:    kobject in question, with which to build the path
5  * @gfp_mask:    the allocation type used to allocate the path
6  *
7  * The result must be freed by the caller with kfree().
8  */
9 char *kobject_get_path(struct kobject *kobj, gfp_t gfp_mask)
10 {
11     char *path;
12     int len;
13
14     /* [cgw]: 根据当前节点kobj，统计从当前节点开始到所有父辈节点的名字
15           * 总长度
16           */
17     len = get_kobj_path_length(kobj);
18     /* [cgw]: 长度为0，错误 */
19     if (len == 0)
20         return NULL;
21     /* [cgw]: 分配长度len个字节的内存空间，并清0内存 */
22     path = kzalloc(len, gfp_mask);
23     if (!path)
24         return NULL;
25     /* [cgw]: 把所有节点对象名字填装到path中 */
26     fill_kobj_path(kobj, path, len);
27
28     return path;
29 }
30 EXPORT_SYMBOL_GPL(kobject_get_path);

1 /**
2  *    kobject_init - initialize object.
3  *    @kobj:    object in question.
4  */
5 void kobject_init(struct kobject * kobj)
6 {
7     /* [cgw]: kobj为空，错误 */
8     if (!kobj)
9         return;
10     /* [cgw]: 初始化kobj->kref引用计数为1 */
11     kref_init(&kobj->kref);
12     /* [cgw]: 初始化kobj->entry链表 */
13     INIT_LIST_HEAD(&kobj->entry);
14     /* [cgw]: 初始化kobj->poll */
15     init_waitqueue_head(&kobj->poll);
16     /* [cgw]: 获得kset成员的指针 */
17     kobj->kset = kset_get(kobj->kset);
18 }

*    unlink - remove kobject from kset list.
*    @kobj:    kobject.
*
*    Remove the kobject from the kset list and decrement
*    its parent's refcount.
*    This is separated out, so we can use it in both
*    kobject_del() and kobject_add() on error.
*/

static void unlink(struct kobject * kobj)
{
    /* [cgw]: kobj所在kobj->kset集合存在 */
    if (kobj->kset) {
        spin_lock(&kobj->kset->list_lock);
        /* [cgw]: 从链表中删除一个kobj条目 */
        list_del_init(&kobj->entry);
        spin_unlock(&kobj->kset->list_lock);
    }
    /* [cgw]: kobj引用计数-1 */
    kobject_put(kobj);
}

/**
*    kobject_shadow_add - add an object to the hierarchy.
*    @kobj:    object.
*    @shadow_parent: sysfs directory to add to.
*/

int kobject_shadow_add(struct kobject * kobj, struct dentry *shadow_parent)
{
    int error = 0;
    struct kobject * parent;

    /* [cgw]: kobj引用计数+1，并返回kobj指针 */
    if (!(kobj = kobject_get(kobj)))
        return -ENOENT;
    /* [cgw]: kobj对象名字为空，即指针为空 */
    if (!kobj->k_name)
        /* [cgw]: 添加名字，k_name指针指向name */
        kobj->k_name = kobj->name;
    /* [cgw]: kobj对象名字为空，即指针为空 */
    if (!*kobj->k_name) {
        pr_debug("kobject attempted to be registered with no name! ");
        WARN_ON(1);
        /* [cgw]: kobj引用计数-1，并返回kobj指针
          * 如果kobj引用计数为0，则kobj将被移除
          */
        kobject_put(kobj);
        return -EINVAL;
    }
    /* [cgw]: 找到kobj的父节点 */
    parent = kobject_get(kobj->parent);

    /* [cgw]: 打印当前节点和上一节点kobj的名字，和所属集合kset的kobj名字*/
    pr_debug("kobject %s: registering. parent: %s, set: %s ",
         kobject_name(kobj), parent ? kobject_name(parent) : "<NULL>",
         kobj->kset ? kobj->kset->kobj.name : "<NULL>" );
    /* [cgw]: kobj所在集合kset指针存在 */
    if (kobj->kset) {
        /* [cgw]: 进入临界区 */
        spin_lock(&kobj->kset->list_lock);
        /* [cgw]: kobj父节点不为空 */
        if (!parent)
            /* [cgw]: 找出kobj的成员kset的kobj对象 */
            parent = kobject_get(&kobj->kset->kobj);
        /* [cgw]: 把当前kobj成员entry插入到kobj->kset->list链表中，
                  * entry插入到kobj->kset->list节点前
                  */
        list_add_tail(&kobj->entry,&kobj->kset->list);
        /* [cgw]: 退出临界区 */
        spin_unlock(&kobj->kset->list_lock);
        /* [cgw]: kobj的父节点指针指向kobj的成员kset的kobj
          * 因为entry已经加入到kobj->kset->list中，即kobj已经加入了kset
          * 集合
          */
        kobj->parent = parent;
    }

    /* [cgw]: 为这个kobj创建目录，即加入到sysfs目录，
          * 并为这个kobj添加属性
          */
    error = create_dir(kobj, shadow_parent);
    /* [cgw]: 创建kobj目录发生错误 */
    if (error) {
        /* unlink does the kobject_put() for us */
        /* [cgw]: 移除当前kobj->entery节点 */
        unlink(kobj);
        /* [cgw]:  kobj父节点引用计数-1*/
        kobject_put(parent);

        /* be noisy on error issues */
        if (error == -EEXIST)
            /* [cgw]: 在相同目录下出现相同的对象名 */
            printk(KERN_ERR "kobject_add failed for %s with "
                   "-EEXIST, don't try to register things with "
                   "the same name in the same directory. ",
                   kobject_name(kobj));
        else
            /* [cgw]: kobject_add操作失败，因本函数是直接在kobject_add调用
                  *
                  */
            printk(KERN_ERR "kobject_add failed for %s (%d) ",
                   kobject_name(kobj), error);
        dump_stack();
    }

    return error;
}

2  *    kobject_add - add an object to the hierarchy.
3  *    @kobj:    object.
4  */
5 int kobject_add(struct kobject * kobj)
6 {
7     /* [cgw]: 添加kobj到层，实际上是把kobj添加到kset集合
8           * entry插入到kobj->kset->list链表中, 为这个kobj创建目录，
9           * 即加入到sysfs目录,并为这个kobj添加属性
10           */
11     return kobject_shadow_add(kobj, NULL);
12 }

2  *    kobject_register - initialize and add an object.
3  *    @kobj:    object in question.
4  */
5
6 int kobject_register(struct kobject * kobj)
7 {
8     int error = -EINVAL;
9     /* [cgw]: 已经定义了一个kobj对象 */
10     if (kobj) {
11         /* [cgw]: 初始化这个kobj对象 */
12         kobject_init(kobj);
13         /* [cgw]: 添加这个kobj到sysfs目录，kset集合 */
14         error = kobject_add(kobj);
15         /* [cgw]: 添加成功 */
16         if (!error)
17             /* [cgw]: 通知用户空间发生了KOBJ_ADD事件 */
18             kobject_uevent(kobj, KOBJ_ADD);
19     }
20     return error;
21 }

2  *    kobject_set_name - Set the name of an object
3  *    @kobj:    object.
4  *    @fmt:    format string used to build the name
5  *
6  *    If strlen(name) >= KOBJ_NAME_LEN, then use a dynamically allocated
7  *    string that @kobj->k_name points to. Otherwise, use the static
8  *    @kobj->name array.
9  */
10 int kobject_set_name(struct kobject * kobj, const char * fmt, ...)
11 {
12     int error = 0;、
13     /* [cgw]: kobj名字长度限制 */
14     int limit = KOBJ_NAME_LEN;
15     int need;
16     va_list args;
17     char * name;
18
19     /*
20      * First, try the static array
21      */
22     /* [cgw]: 格式化参数中的字符到kobj->name数组 */
23     va_start(args,fmt);
24     need = vsnprintf(kobj->name,limit,fmt,args);
25     va_end(args);
26     /* [cgw]: 长度在限制以内 */
27     if (need < limit)
28         /* [cgw]: name指向kobj->name */
29         name = kobj->name;
30     else {
31         /*
32          * Need more space? Allocate it and try again
33          */
34         /* [cgw]: 长度超出限制以外 */
35         limit = need + 1;
36         /* [cgw]: 分配长度为need + 1个字节的内存空间 */
37         name = kmalloc(limit,GFP_KERNEL);
38         /* [cgw]: 分配失败 */
39         if (!name) {
40             error = -ENOMEM;
41             goto Done;
42         }
43         /* [cgw]: 重新格式化到name */
44         va_start(args,fmt);
45         need = vsnprintf(name,limit,fmt,args);
46         va_end(args);
47
48         /* Still? Give up. */
49         /* [cgw]: 还是不够? 算了，有心无力了 */
50         if (need >= limit) {
51             /* [cgw]: 释放分配给name的内存空间 */
52             kfree(name);
53             error = -EFAULT;
54             goto Done;
55         }
56     }
57
58     /* Free the old name, if necessary. */
59     /* [cgw]: 旧的名字不要了 */
60     if (kobj->k_name && kobj->k_name != kobj->name)
61         /* [cgw]: 释放旧名字的内存空间 */
62         kfree(kobj->k_name);
63
64     /* Now, set the new name */
65     /* [cgw]: 重置新名字 */
66     kobj->k_name = name;
67  Done:
68     return error;
69 }
70
71 EXPORT_SYMBOL(kobject_set_name);

2  *    kobject_rename - change the name of an object
3  *    @kobj:    object in question.
4  *    @new_name: object's new name
5  */
6
7 int kobject_rename(struct kobject * kobj, const char *new_name)
8 {
9     int error = 0;
10     const char *devpath = NULL;
11     char *devpath_string = NULL;
12     char *envp[2];
13
14     /* [cgw]: kobj引用计数+1 */
15     kobj = kobject_get(kobj);
16     /* [cgw]: kobj为空 */
17     if (!kobj)
18         return -EINVAL;
19     /* [cgw]: kobj的父节点为空 */
20     if (!kobj->parent)
21         return -EINVAL;
22     /* [cgw]: 获得当前节点kobj和所有父节点的名字 */
23     devpath = kobject_get_path(kobj, GFP_KERNEL);
24     /* [cgw]: 获取失败 */
25     if (!devpath) {
26         error = -ENOMEM;
27         goto out;
28     }
29     /* [cgw]: 分配strlen(devpath) + 15字节内存空间 */
30     devpath_string = kmalloc(strlen(devpath) + 15, GFP_KERNEL);
31     /* [cgw]: 分配失败 */
32     if (!devpath_string) {
33         error = -ENOMEM;
34         goto out;
35     }
36     /* [cgw]: 格式化"DEVPATH_OLD=%s" + devpath 存到devpath_string */
37     sprintf(devpath_string, "DEVPATH_OLD=%s", devpath);
38     /* [cgw]: 存入环境变量 */
39     envp[0] = devpath_string;
40     envp[1] = NULL;
41     /* Note : if we want to send the new name alone, not the full path,
42      * we could probably use kobject_name(kobj); */
43     /* [cgw]: 重命名kobj对象 */
44     error = sysfs_rename_dir(kobj, kobj->parent->dentry, new_name);
45
46     /* This function is mostly/only used for network interface.
47      * Some hotplug package track interfaces by their name and
48      * therefore want to know when the name is changed by the user. */
49     /* [cgw]: 重命名成功 */
50     if (!error)
51         /* [cgw]: 发送一个用户事件KOBJ_MOVE，和环境变量 */
52         kobject_uevent_env(kobj, KOBJ_MOVE, envp);
53
54 out:
55     /* [cgw]: 释放devpath_string和devpath内存 */
56     kfree(devpath_string);
57     kfree(devpath);
58     /* [cgw]: kobj引用计数-1，并删除kobj */
59     kobject_put(kobj);
60
61     return error;
62 }

2  *    kobject_rename - change the name of an object
3  *    @kobj:    object in question.
4  *    @new_parent: object's new parent
5  *    @new_name: object's new name
6  */
7
8 int kobject_shadow_rename(struct kobject * kobj, struct dentry *new_parent,
9               const char *new_name)
10 {
11     int error = 0;
12     /* [cgw]: kobj引用计数+1*/
13     kobj = kobject_get(kobj);
14     if (!kobj)
15         return -EINVAL;
16     /* [cgw]: 重命名kobj对象 */
17     error = sysfs_rename_dir(kobj, new_parent, new_name);
18     /* [cgw]: kobj引用计数-1，并删除kobj */
19     kobject_put(kobj);
20
21     return error;
22 }

2  *    kobject_move - move object to another parent
3  *    @kobj:    object in question.
4  *    @new_parent: object's new parent (can be NULL)
5  */
6
7 int kobject_move(struct kobject *kobj, struct kobject *new_parent)
8 {
9     int error;
10     struct kobject *old_parent;
11     const char *devpath = NULL;
12     char *devpath_string = NULL;
13     char *envp[2];
14
15     /* [cgw]: kobj引用计数+1*/
16     kobj = kobject_get(kobj);
17     /* [cgw]: kobj指针为空*/
18     if (!kobj)
19         return -EINVAL;
20     /* [cgw]: kobj父节点引用计数+1*/
21     new_parent = kobject_get(new_parent);
22     /* [cgw]: kobj指针为空*/
23     if (!new_parent) {
24         /* [cgw]: kobj所属kset存在 */
25         if (kobj->kset)
26             /* [cgw]: kobj->kset->kobj引用计数+1
27                   */
28             new_parent = kobject_get(&kobj->kset->kobj);
29     }
30     /* old object path */
31     /* [cgw]: 获得kobj 和所有父节点对象名字，即路径名*/
32     devpath = kobject_get_path(kobj, GFP_KERNEL);
33     /* [cgw]: 获取失败 */
34     if (!devpath) {
35         error = -ENOMEM;
36         goto out;
37     }
38     /* [cgw]: 分配strlen(devpath) + 15字节内存空间 */
39     devpath_string = kmalloc(strlen(devpath) + 15, GFP_KERNEL);
40     /* [cgw]: 分配失败 */
41     if (!devpath_string) {
42         error = -ENOMEM;
43         goto out;
44     }
45     /* [cgw]: 格式化"DEVPATH_OLD=%s" + devpath 存到devpath_string */
46     sprintf(devpath_string, "DEVPATH_OLD=%s", devpath);
47     /* [cgw]: 存入环境变量 */
48     envp[0] = devpath_string;
49     envp[1] = NULL;
50     /* [cgw]: 移动kobj到新的父节点对象 */
51     error = sysfs_move_dir(kobj, new_parent);
52     /* [cgw]: 失败 */
53     if (error)
54         goto out;
55     /* [cgw]: 记录kobj旧的的父节点对象 */
56     old_parent = kobj->parent;
57     /* [cgw]: 用新的父节点对象代替旧的 */
58     kobj->parent = new_parent;
59     new_parent = NULL;
60     /* [cgw]: kobj旧的父节点对象引用计数-1，并删除旧的父节点对象 */
61     kobject_put(old_parent);
62     /* [cgw]: 发送一个用户事件KOBJ_MOVE，和环境变量 */
63     kobject_uevent_env(kobj, KOBJ_MOVE, envp);
64 out:
65     /* [cgw]: kobj新的父节点对象引用计数-1，并删除新的父节点对象 */
66     kobject_put(new_parent);
67     /* [cgw]: kobj引用计数-1，并删除kobj */
68     kobject_put(kobj);
69     /* [cgw]: 释放devpath_string和devpath内存 */
70     kfree(devpath_string);
71     kfree(devpath);
72     return error;
73 }

2  *    kobject_del - unlink kobject from hierarchy.
3  *     @kobj:    object.
4  */
5
6 void kobject_del(struct kobject * kobj)
7 {
8     /* [cgw]: kobj对象不存在 */
9     if (!kobj)
10         return;
11     /* [cgw]: 从sysfs目录移除kobj对象，清0 kobj->dentry节点 */
12     sysfs_remove_dir(kobj);
13     /* [cgw]: 删除kobj->dentry节点 */
14     unlink(kobj);
15 }

2  *    kobject_unregister - remove object from hierarchy and decrement refcount.
3  *    @kobj:    object going away.
4  */
5
6 void kobject_unregister(struct kobject * kobj)
7 {
8     if (!kobj)
9         return;
10     pr_debug("kobject %s: unregistering ",kobject_name(kobj));
11     /* [cgw]: 通知用户空间发生了KOBJ_REMOVE事件 */
12     kobject_uevent(kobj, KOBJ_REMOVE);
13     /* [cgw]: 从sysfs目录删除kobj对象(删除kobj->entery, kobj->kset->list节点) */
14     kobject_del(kobj);
15     /* [cgw]: 删除kobj对象，释放内存空间 */
16     kobject_put(kobj);
17 }

2  *    kobject_get - increment refcount for object.
3  *    @kobj:    object.
4  */
5
6 struct kobject * kobject_get(struct kobject * kobj)
7 {
8     /* [cgw]: 指针不为空 */
9     if (kobj)
10         /* [cgw]: 引用计数+1 */
11         kref_get(&kobj->kref);
12     return kobj;
13 }

2  *    kobject_cleanup - free kobject resources.
3  *    @kobj:    object.
4  */
5
6 void kobject_cleanup(struct kobject * kobj)
7 {
8     /* [cgw]: 找到kobj->ktype */
9     struct kobj_type * t = get_ktype(kobj);
10     struct kset * s = kobj->kset;
11     struct kobject * parent = kobj->parent;
12
13     pr_debug("kobject %s: cleaning up ",kobject_name(kobj));
14     /* [cgw]: k_name没有指向name */
15     if (kobj->k_name != kobj->name)
16         /* [cgw]: 释放k_name内存空间 */
17         kfree(kobj->k_name);
18     /* [cgw]: k_name指针清零 */
19     kobj->k_name = NULL;
20     /* [cgw]: ktype定义的release函数 */
21     if (t && t->release)
22         /* [cgw]: 删除kobj，并释放内存 */
23         t->release(kobj);
24     if (s)
25         /* [cgw]: kobj->kset->kobj引用计数-1 */
26         kset_put(s);
27     /* [cgw]: kobj父节点引用计数-1 */
28     kobject_put(parent);
29 }

2 {
3     /* [cgw]: 删除kobj->k_name, kobj, kobj->parent, kobj->kset,
4           * 调用kobj->ktype->release
5           */
6     kobject_cleanup(container_of(kref, struct kobject, kref));
7 }

2  *    kobject_put - decrement refcount for object.
3  *    @kobj:    object.
4  *
5  *    Decrement the refcount, and if 0, call kobject_cleanup().
6  */
7 void kobject_put(struct kobject * kobj)
8 {
9     /* [cgw]: 指针不为空 */
10     if (kobj)
11         /* [cgw]: 引用计数-1 ，kobj->kref为0时，调用kobject_release */
12         kref_put(&kobj->kref, kobject_release);
13 }

2 {
3 /* [cgw]: 释放kobj内存空间 */
4 kfree(kobj);
5 }

2     .release    = dir_release,
3     .sysfs_ops    = NULL,
4     .default_attrs    = NULL,
5 };

2  *    kobject_kset_add_dir - add sub directory of object.
3  *    @kset:        kset the directory is belongs to.
4  *    @parent:    object in which a directory is created.
5  *    @name:    directory name.
6  *
7  *    Add a plain directory object as child of given object.
8  */
9 struct kobject *kobject_kset_add_dir(struct kset *kset,
10                      struct kobject *parent, const char *name)
11 {
12     struct kobject *k;
13     int ret;
14
15     /* [cgw]: parent指针为空 */
16     if (!parent)
17         return NULL;
18
19     /* [cgw]: 分配一个struct kobject的内存空间 */
20     k = kzalloc(sizeof(*k), GFP_KERNEL);
21     /* [cgw]: 分配失败 */
22     if (!k)
23         return NULL;
24
25     /* [cgw]: 分配kobj->kset */
26     k->kset = kset;
27     /* [cgw]: 分配kobj->parent */
28     k->parent = parent;
29     /* [cgw]: 分配kobj->ktype */
30     k->ktype = &dir_ktype;
31     /* [cgw]: 给kobj->k_name分配名字 */
32     kobject_set_name(k, name);
33     /* [cgw]: 注册kobj */
34     ret = kobject_register(k);
35     /* [cgw]: 注册失败 */
36     if (ret < 0) {
37         printk(KERN_WARNING "%s: kobject_register error: %d ",
38             __func__, ret);
39         /* [cgw]: 删除kobj */
40         kobject_del(k);
41         return NULL;
42     }
43
44     return k;
45 }

2  *    kobject_add_dir - add sub directory of object.
3  *    @parent:    object in which a directory is created.
4  *    @name:    directory name.
5  *
6  *    Add a plain directory object as child of given object.
7  */
8 struct kobject *kobject_add_dir(struct kobject *parent, const char *name)
9 {
10     /* [cgw]: 添加一个kobj对象子目录
11           * kobj->kset为空
12           */
13     return kobject_kset_add_dir(NULL, parent, name);
14 }

2  *    kset_init - initialize a kset for use
3  *    @k:    kset
4  */
5
6 void kset_init(struct kset * k)
7 {
8     /* [cgw]: 初始化kset成员kobj对象 */
9     kobject_init(&k->kobj);
10     /* [cgw]: 初始化kset成员list链表 */
11     INIT_LIST_HEAD(&k->list);
12     /* [cgw]: 初始化保护kset成员list链表的自旋锁 */
13     spin_lock_init(&k->list_lock);
14 }

2  *    kset_add - add a kset object to the hierarchy.
3  *    @k:    kset.
4  */
5
6 int kset_add(struct kset * k)
7 {
8     /* [cgw]: 添加kset成员kobj对象
9           *
10           */
11     return kobject_add(&k->kobj);
12 }

2  *    kset_register - initialize and add a kset.
3  *    @k:    kset.
4  */
5
6 int kset_register(struct kset * k)
7 {
8     /* [cgw]: 指针为空 */
9     if (!k)
10         return -EINVAL;
11     /* [cgw]: 初始化并添加kset */
12     kset_init(k);
13     return kset_add(k);
14 }

2  *    kset_unregister - remove a kset.
3  *    @k:    kset.
4  */
5
6 void kset_unregister(struct kset * k)
7 {
8     /* [cgw]: 指针为空 */
9     if (!k)
10         return;
11     /* [cgw]: 删除kset，实际是删除kset->kobj */
12     kobject_unregister(&k->kobj);
13 }

2  *    kset_find_obj - search for object in kset.
3  *    @kset:    kset we're looking in.
4  *    @name:    object's name.
5  *
6  *    Lock kset via @kset->subsys, and iterate over @kset->list,
7  *    looking for a matching kobject. If matching object is found
8  *    take a reference and return the object.
9  */
10
11 struct kobject * kset_find_obj(struct kset * kset, const char * name)
12 {
13     struct list_head * entry;
14     struct kobject * ret = NULL;
15
16     /* [cgw]: 进入临界区 */
17     spin_lock(&kset->list_lock);
18     /* [cgw]: 以kset->list为头节点开始轮询kset->list链表中
19       * 每个节点，取出存到entry
20       */
21     list_for_each(entry,&kset->list) {
22         /* [cgw]: 取出一个entry，根据这个entry，找到对应kobj
23               */
24         struct kobject * k = to_kobj(entry);
25         /* [cgw]: 找到对应的kobj，这个kobj的名字是否是要找的kobj的名字匹配 */
26         if (kobject_name(k) && !strcmp(kobject_name(k),name)) {
27             /* [cgw]: 找到了这个kobj，引用计数+1 */
28             ret = kobject_get(k);
29             break;
30         }
31     }
32     /* [cgw]: 退出临界区 */
33     spin_unlock(&kset->list_lock);
34     return ret;
35 }

2 {
3     /* [cgw]: 初始化kset，每一个 kset都属于一个子系统
4           * Every kset must belong to a subsystem. The subsystem
5           * membership helps establish the kset's position in the hierarchy
6           * <Linux Device Drivers>
7           */
8     kset_init(s);
9 }
10
11 int subsystem_register(struct kset *s)
12 {
13     /* [cgw]: 注册kset */
14     return kset_register(s);
15 }
16
17 void subsystem_unregister(struct kset *s)
18 {
19     /* [cgw]: 注销kset */
20     kset_unregister(s);
21 }
22
23 /**
24  *    subsystem_create_file - export sysfs attribute file.
25  *    @s:    subsystem.
26  *    @a:    subsystem attribute descriptor.
27  */
28
29 int subsys_create_file(struct kset *s, struct subsys_attribute *a)
30 {
31     int error = 0;
32
33     if (!s || !a)
34         return -EINVAL;
35     /* [cgw]: 这个操作最终导致，kset->kobj引用计数+1
36           * 并返回ket指针
37           */
38     if (subsys_get(s)) {
39         /* [cgw]: 为kset->kobj这个对象创建一个属性文件 */
40         error = sysfs_create_file(&s->kobj, &a->attr);
41         /* [cgw]: 这个操作最终导致，kset->kobj引用计数-1
42                   * 并返回kset指针
43                   */
44         subsys_put(s);
45     }
46     return error;
47 }
48
49 EXPORT_SYMBOL(kobject_init);
50 EXPORT_SYMBOL(kobject_register);
51 EXPORT_SYMBOL(kobject_unregister);
52 EXPORT_SYMBOL(kobject_get);
53 EXPORT_SYMBOL(kobject_put);
54 EXPORT_SYMBOL(kobject_add);
55 EXPORT_SYMBOL(kobject_del);
56
57 EXPORT_SYMBOL(kset_register);
58 EXPORT_SYMBOL(kset_unregister);
59
60 EXPORT_SYMBOL(subsystem_register);
61 EXPORT_SYMBOL(subsystem_unregister);
62 EXPORT_SYMBOL(subsys_create_file);