kobject.c 添加注释

最近结合《Linux Device Drivers》对kobject的理解，对kobject.c文件添加注释，仅供参考！



1 /**

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.

*

*/

static int populate_dir(struct kobject * kobj)

{

/* [cgw]: 从kobject取出kobj_type成员指针 */

struct kobj_type * t = get_ktype(kobj);

struct attribute * attr;

int error = 0;

int i;

/* [cgw]: kobj_type中默认属性default_attrs不为空，即已经添加一个或以上

* 属性项

*/

if (t && t->default_attrs) {

/* [cgw]: 轮询default_attrs中的指针不为空，即已经添加属性 */

for (i = 0; (attr = t->default_attrs[i]) != NULL; i++) {

/* [cgw]: 在sysfs中为这个kobj创建一个属性文件 */

if ((error = sysfs_create_file(kobj,attr)))

break;

}

}

return error;

}

1 static int create_dir(struct kobject * kobj, struct dentry *shadow_parent)

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 */

error = sysfs_create_dir(kobj, shadow_parent);

if (!error) {

/* [cgw]: 添加kobj属性*/

if ((error = populate_dir(kobj)))

/* [cgw]: 添加失败，删除kobj对象目录 */

sysfs_remove_dir(kobj);

}

}

return error;

}

1 static inline struct kobject * to_kobj(struct list_head * entry)

{

/* [cgw]: 从链表list_head取出一个entry

* 根据这个entry，找到包含这个entry的

* kobject结构体地址

*/

return container_of(entry,struct kobject,entry);

}

1 static int get_kobj_path_length(struct kobject *kobj)

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 */

/* [cgw]: 逐个节点查找对象的名字，计算每节点对象的名字长度，

* 并加1，加1是每个名字前有个'/'，并累计所有名字长度

*/

do {

/* [cgw]: 名字不为空 */

if (kobject_name(parent) == NULL)

return 0;

/* [cgw]: 累计名字长度 */

length += strlen(kobject_name(parent)) + 1;

/* [cgw]: 指向上一节点(当前对象的父辈) */

parent = parent->parent;

} while (parent);

return length;

}

1 static void fill_kobj_path(struct kobject *kobj, char *path, int length)

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));

/* back up enough to print this name with '/' */

/* [cgw]: 总长度减去一个名字的长度 */

length -= cur;

/* [cgw]: 把这个对象名字填装到path的path + length位置 */

strncpy (path + length, kobject_name(parent), cur);

/* [cgw]: 在path的path + length -1的位置插入'/' */

*(path + --length) = '/';

}

pr_debug("%s: path = '%s'\n",__FUNCTION__,path);

}

1 /**

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)

{

char *path;

int len;

/* [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

* 总长度

*/

len = get_kobj_path_length(kobj);

/* [cgw]: 长度为0，错误 */

if (len == 0)

return NULL;

/* [cgw]: 分配长度len个字节的内存空间，并清0内存 */

path = kzalloc(len, gfp_mask);

if (!path)

return NULL;

/* [cgw]: 把所有节点对象名字填装到path中 */

fill_kobj_path(kobj, path, len);

return path;

}

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;

/* [cgw]: 初始化kobj->kref引用计数为1 */

kref_init(&kobj->kref);

/* [cgw]: 初始化kobj->entry链表 */

INIT_LIST_HEAD(&kobj->entry);

/* [cgw]: 初始化kobj->poll */

init_waitqueue_head(&kobj->poll);

/* [cgw]: 获得kset成员的指针 */

kobj->kset = kset_get(kobj->kset);

}

/**

* 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!\n");

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\n",

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.\n",

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)\n",

kobject_name(kobj), error);

dump_stack();

}

return error;

}

1 /**

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

*/

return kobject_shadow_add(kobj, NULL);

}

1 /**

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 */

if (kobj) {

/* [cgw]: 初始化这个kobj对象 */

kobject_init(kobj);

/* [cgw]: 添加这个kobj到sysfs目录，kset集合 */

error = kobject_add(kobj);

/* [cgw]: 添加成功 */

if (!error)

/* [cgw]: 通知用户空间发生了KOBJ_ADD事件 */

kobject_uevent(kobj, KOBJ_ADD);

}

return error;

}

1 /**

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 */

int kobject_set_name(struct kobject * kobj, const char * fmt, ...)

{

int error = 0;、

/* [cgw]: kobj名字长度限制 */

int limit = KOBJ_NAME_LEN;

int need;

va_list args;

char * name;

/*

* First, try the static array

*/

/* [cgw]: 格式化参数中的字符到kobj->name数组 */

va_start(args,fmt);

need = vsnprintf(kobj->name,limit,fmt,args);

va_end(args);

/* [cgw]: 长度在限制以内 */

if (need < limit)

/* [cgw]: name指向kobj->name */

name = kobj->name;

else {

/*

* Need more space? Allocate it and try again

*/

/* [cgw]: 长度超出限制以外 */

limit = need + 1;

/* [cgw]: 分配长度为need + 1个字节的内存空间 */

name = kmalloc(limit,GFP_KERNEL);

/* [cgw]: 分配失败 */

if (!name) {

error = -ENOMEM;

goto Done;

}

/* [cgw]: 重新格式化到name */

va_start(args,fmt);

need = vsnprintf(name,limit,fmt,args);

va_end(args);

/* Still? Give up. */

/* [cgw]: 还是不够? 算了，有心无力了 */

if (need >= limit) {

/* [cgw]: 释放分配给name的内存空间 */

kfree(name);

error = -EFAULT;

goto Done;

}

}

/* Free the old name, if necessary. */

/* [cgw]: 旧的名字不要了 */

if (kobj->k_name && kobj->k_name != kobj->name)

/* [cgw]: 释放旧名字的内存空间 */

kfree(kobj->k_name);

/* Now, set the new name */

/* [cgw]: 重置新名字 */

kobj->k_name = name;

Done:

return error;

}

EXPORT_SYMBOL(kobject_set_name);

1 /**

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;

const char *devpath = NULL;

char *devpath_string = NULL;

char *envp[2];

/* [cgw]: kobj引用计数+1 */

kobj = kobject_get(kobj);

/* [cgw]: kobj为空 */

if (!kobj)

return -EINVAL;

/* [cgw]: kobj的父节点为空 */

if (!kobj->parent)

return -EINVAL;

/* [cgw]: 获得当前节点kobj和所有父节点的名字 */

devpath = kobject_get_path(kobj, GFP_KERNEL);

/* [cgw]: 获取失败 */

if (!devpath) {

error = -ENOMEM;

goto out;

}

/* [cgw]: 分配strlen(devpath) + 15字节内存空间 */

devpath_string = kmalloc(strlen(devpath) + 15, GFP_KERNEL);

/* [cgw]: 分配失败 */

if (!devpath_string) {

error = -ENOMEM;

goto out;

}

/* [cgw]: 格式化"DEVPATH_OLD=%s" + devpath 存到devpath_string */

sprintf(devpath_string, "DEVPATH_OLD=%s", devpath);

/* [cgw]: 存入环境变量 */

envp[0] = devpath_string;

envp[1] = NULL;

/* Note : if we want to send the new name alone, not the full path,

* we could probably use kobject_name(kobj); */

/* [cgw]: 重命名kobj对象 */

error = sysfs_rename_dir(kobj, kobj->parent->dentry, new_name);

/* This function is mostly/only used for network interface.

* Some hotplug package track interfaces by their name and

* therefore want to know when the name is changed by the user. */

/* [cgw]: 重命名成功 */

if (!error)

/* [cgw]: 发送一个用户事件KOBJ_MOVE，和环境变量 */

kobject_uevent_env(kobj, KOBJ_MOVE, envp);

out:

/* [cgw]: 释放devpath_string和devpath内存 */

kfree(devpath_string);

kfree(devpath);

/* [cgw]: kobj引用计数-1，并删除kobj */

kobject_put(kobj);

return error;

}

1 /**

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)

{

int error = 0;

/* [cgw]: kobj引用计数+1*/

kobj = kobject_get(kobj);

if (!kobj)

return -EINVAL;

/* [cgw]: 重命名kobj对象 */

error = sysfs_rename_dir(kobj, new_parent, new_name);

/* [cgw]: kobj引用计数-1，并删除kobj */

kobject_put(kobj);

return error;

}

1 /**

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;

struct kobject *old_parent;

const char *devpath = NULL;

char *devpath_string = NULL;

char *envp[2];

/* [cgw]: kobj引用计数+1*/

kobj = kobject_get(kobj);

/* [cgw]: kobj指针为空*/

if (!kobj)

return -EINVAL;

/* [cgw]: kobj父节点引用计数+1*/

new_parent = kobject_get(new_parent);

/* [cgw]: kobj指针为空*/

if (!new_parent) {

/* [cgw]: kobj所属kset存在 */

if (kobj->kset)

/* [cgw]: kobj->kset->kobj引用计数+1

*/

new_parent = kobject_get(&kobj->kset->kobj);

}

/* old object path */

/* [cgw]: 获得kobj 和所有父节点对象名字，即路径名*/

devpath = kobject_get_path(kobj, GFP_KERNEL);

/* [cgw]: 获取失败 */

if (!devpath) {

error = -ENOMEM;

goto out;

}

/* [cgw]: 分配strlen(devpath) + 15字节内存空间 */

devpath_string = kmalloc(strlen(devpath) + 15, GFP_KERNEL);

/* [cgw]: 分配失败 */

if (!devpath_string) {

error = -ENOMEM;

goto out;

}

/* [cgw]: 格式化"DEVPATH_OLD=%s" + devpath 存到devpath_string */

sprintf(devpath_string, "DEVPATH_OLD=%s", devpath);

/* [cgw]: 存入环境变量 */

envp[0] = devpath_string;

envp[1] = NULL;

/* [cgw]: 移动kobj到新的父节点对象 */

error = sysfs_move_dir(kobj, new_parent);

/* [cgw]: 失败 */

if (error)

goto out;

/* [cgw]: 记录kobj旧的的父节点对象 */

old_parent = kobj->parent;

/* [cgw]: 用新的父节点对象代替旧的 */

kobj->parent = new_parent;

new_parent = NULL;

/* [cgw]: kobj旧的父节点对象引用计数-1， 并删除旧的父节点对象 */

kobject_put(old_parent);

/* [cgw]: 发送一个用户事件KOBJ_MOVE，和环境变量 */

kobject_uevent_env(kobj, KOBJ_MOVE, envp);

out:

/* [cgw]: kobj新的父节点对象引用计数-1， 并删除新的父节点对象 */

kobject_put(new_parent);

/* [cgw]: kobj引用计数-1， 并删除kobj */

kobject_put(kobj);

/* [cgw]: 释放devpath_string和devpath内存 */

kfree(devpath_string);

kfree(devpath);

return error;

}

1 /**

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)

return;

/* [cgw]: 从sysfs目录移除kobj对象，清0 kobj->dentry节点 */

sysfs_remove_dir(kobj);

/* [cgw]: 删除kobj->dentry节点 */

unlink(kobj);

}

1 /**

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;

pr_debug("kobject %s: unregistering\n",kobject_name(kobj));

/* [cgw]: 通知用户空间发生了KOBJ_REMOVE事件 */

kobject_uevent(kobj, KOBJ_REMOVE);

/* [cgw]: 从sysfs目录删除kobj对象(删除kobj->entery, kobj->kset->list节点) */

kobject_del(kobj);

/* [cgw]: 删除kobj对象，释放内存空间 */

kobject_put(kobj);

}

1 /**

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)

/* [cgw]: 引用计数+1 */

kref_get(&kobj->kref);

return kobj;

}

1 /**

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);

struct kset * s = kobj->kset;

struct kobject * parent = kobj->parent;

pr_debug("kobject %s: cleaning up\n",kobject_name(kobj));

/* [cgw]: k_name没有指向name */

if (kobj->k_name != kobj->name)

/* [cgw]: 释放k_name内存空间 */

kfree(kobj->k_name);

/* [cgw]: k_name指针清零 */

kobj->k_name = NULL;

/* [cgw]: ktype定义的release函数 */

if (t && t->release)

/* [cgw]: 删除kobj，并释放内存 */

t->release(kobj);

if (s)

/* [cgw]: kobj->kset->kobj引用计数-1 */

kset_put(s);

/* [cgw]: kobj父节点引用计数-1 */

kobject_put(parent);

}

1 static void kobject_release(struct kref *kref)

{

/* [cgw]: 删除kobj->k_name, kobj, kobj->parent, kobj->kset,

* 调用kobj->ktype->release

*/

kobject_cleanup(container_of(kref, struct kobject, kref));

}

1 /**

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 */

if (kobj)

/* [cgw]: 引用计数-1 ，kobj->kref为0时，调用kobject_release */

kref_put(&kobj->kref, kobject_release);

}

1 static void dir_release(struct kobject *kobj)

{

/* [cgw]: 释放kobj内存空间 */

kfree(kobj);

}

1 static struct kobj_type dir_ktype = {

.release = dir_release,

.sysfs_ops = NULL,

.default_attrs = NULL,

};

1 /**

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,

struct kobject *parent, const char *name)

{

struct kobject *k;

int ret;

/* [cgw]: parent指针为空 */

if (!parent)

return NULL;

/* [cgw]: 分配一个struct kobject的内存空间 */

k = kzalloc(sizeof(*k), GFP_KERNEL);

/* [cgw]: 分配失败 */

if (!k)

return NULL;

/* [cgw]: 分配kobj->kset */

k->kset = kset;

/* [cgw]: 分配kobj->parent */

k->parent = parent;

/* [cgw]: 分配kobj->ktype */

k->ktype = &dir_ktype;

/* [cgw]: 给kobj->k_name分配名字 */

kobject_set_name(k, name);

/* [cgw]: 注册kobj */

ret = kobject_register(k);

/* [cgw]: 注册失败 */

if (ret < 0) {

printk(KERN_WARNING "%s: kobject_register error: %d\n",

__func__, ret);

/* [cgw]: 删除kobj */

kobject_del(k);

return NULL;

}

return k;

}

1 /**

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 {

/* [cgw]: 添加一个kobj对象子目录

* kobj->kset为空

*/

return kobject_kset_add_dir(NULL, parent, name);

}

1 /**

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);

/* [cgw]: 初始化kset成员list链表 */

INIT_LIST_HEAD(&k->list);

/* [cgw]: 初始化保护kset成员list链表的自旋锁 */

spin_lock_init(&k->list_lock);

}

1 /**

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 *

*/

return kobject_add(&k->kobj);

}

1 /**

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)

return -EINVAL;

/* [cgw]: 初始化并添加kset */

kset_init(k);

return kset_add(k);

}

1 /**

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)

return;

/* [cgw]: 删除kset，实际是删除kset->kobj */

kobject_unregister(&k->kobj);

}

1 /**

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 */

struct kobject * kset_find_obj(struct kset * kset, const char * name)

{

struct list_head * entry;

struct kobject * ret = NULL;

/* [cgw]: 进入临界区 */

spin_lock(&kset->list_lock);

/* [cgw]: 以kset->list为头节点开始轮询kset->list链表中

* 每个节点，取出存到entry

*/

list_for_each(entry,&kset->list) {

/* [cgw]: 取出一个entry，根据这个entry，找到对应kobj

*/

struct kobject * k = to_kobj(entry);

/* [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 */

if (kobject_name(k) && !strcmp(kobject_name(k),name)) {

/* [cgw]: 找到了这个kobj，引用计数+1 */

ret = kobject_get(k);

break;

}

}

/* [cgw]: 退出临界区 */

spin_unlock(&kset->list_lock);

return ret;

}

1 void subsystem_init(struct kset *s)

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 }

int subsystem_register(struct kset *s)

{

/* [cgw]: 注册kset */

return kset_register(s);

}

void subsystem_unregister(struct kset *s)

{

/* [cgw]: 注销kset */

kset_unregister(s);

}

/**

* subsystem_create_file - export sysfs attribute file.

* @s: subsystem.

* @a: subsystem attribute descriptor.

*/

int subsys_create_file(struct kset *s, struct subsys_attribute *a)

{

int error = 0;

if (!s || !a)

return -EINVAL;

/* [cgw]: 这个操作最终导致，kset->kobj引用计数+1

* 并返回ket指针

*/

if (subsys_get(s)) {

/* [cgw]: 为kset->kobj这个对象创建一个属性文件 */

error = sysfs_create_file(&s->kobj, &a->attr);

/* [cgw]: 这个操作最终导致，kset->kobj引用计数-1

* 并返回kset指针

*/

subsys_put(s);

}

return error;

}

EXPORT_SYMBOL(kobject_init);

EXPORT_SYMBOL(kobject_register);

EXPORT_SYMBOL(kobject_unregister);

EXPORT_SYMBOL(kobject_get);

EXPORT_SYMBOL(kobject_put);

EXPORT_SYMBOL(kobject_add);

EXPORT_SYMBOL(kobject_del);

EXPORT_SYMBOL(kset_register);

EXPORT_SYMBOL(kset_unregister);

EXPORT_SYMBOL(subsystem_register);

EXPORT_SYMBOL(subsystem_unregister);

EXPORT_SYMBOL(subsys_create_file);