总听有人说 Linux kernel 拥有一团无比巨大看似杂乱无章其实有迹可循的链表，今天参考一下其他大牛的相关资料记录一下。
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kset 结构体
151 /**
152 * struct kset - a set of kobjects of a specific type, belonging to a specific subsystem.
153 *
154 * A kset defines a group of kobjects. They can be individually
155 * different "types" but overall these kobjects all want to be grouped
156 * together and operated on in the same manner. ksets are used to
157 * define the attribute callbacks and other common events that happen to
158 * a kobject.
159 *
160 * @list: the list of all kobjects for this kset
161 * @list_lock: a lock for iterating over the kobjects
162 * @kobj: the embedded kobject for this kset (recursion, isn't it fun...)
163 * @uevent_ops: the set of uevent operations for this kset. These are
164 * called whenever a kobject has something happen to it so that the kset
165 * can add new environment variables, or filter out the uevents if so
166 * desired.
167 */
168 struct kset {
169 struct list_head list; // 这里边包含了这个 kset 所有的 kobject
170 spinlock_t list_lock;
171 struct kobject kobj; // 一个嵌入在里面的kobject
172 const struct kset_uevent_ops *uevent_ops; // 里面包含热拔插事件发生时的响应操作
173 };
// include/linux/kobject.h
63 struct kobject {
64 const char *name; // 名字
65 struct list_head entry; // 连接到 kset 建立层次结构
66 struct kobject *parent; // 上一个节点
67 struct kset *kset; // 指向所属的 kset
68 struct kobj_type *ktype; // 指向所属的 ktype
69 struct kernfs_node *sd; /* sysfs directory entry */ // 文件系统内的sysfs 的node
70 struct kref kref; // 引用计数
71 #ifdef CONFIG_DEBUG_KOBJECT_RELEASE
72 struct delayed_work release;
73 #endif
74 unsigned int state_initialized:1; // 初始化状态，只占 1 个位的空间，应用了位域
75 unsigned int state_in_sysfs:1;
76 unsigned int state_add_uevent_sent:1;
77 unsigned int state_remove_uevent_sent:1;
78 unsigned int uevent_suppress:1;
79 };
116 struct kobj_type {
117 void (*release)(struct kobject *kobj);
118 const struct sysfs_ops *sysfs_ops;
119 struct attribute **default_attrs;
120 const struct kobj_ns_type_operations *(*child_ns_type)(struct kobject *kobj);
121 const void *(*namespace)(struct kobject *kobj);
122 };
// lib/kobject.c
// 318 * This function will properly initialize a kobject such that it can then
// 319 * be passed to the kobject_add() call. 等下还有kobject_add()
// 321 * After this function is called, the kobject MUST be cleaned up by a call
// 322 * to kobject_put(), not by a call to kfree directly to ensure that all of
// 323 * the memory is cleaned up properly. 必须用 kobject_put 去释放，而不是 kfree
325 void kobject_init(struct kobject *kobj, struct kobj_type *ktype)
326 {
327 char *err_str;
328
329 if (!kobj) {
330 err_str = "invalid kobject pointer!";
331 goto error;
332 }
333 if (!ktype) {
334 err_str = "must have a ktype to be initialized properly!
";
335 goto error;
336 }
337 if (kobj->state_initialized) {
338 /* do not error out as sometimes we can recover */
339 printk(KERN_ERR "kobject (%p): tried to init an initialized "
340 "object, something is seriously wrong.
", kobj);
341 dump_stack();
342 }
343
344 kobject_init_internal(kobj); // 初始化有关的成员
345 kobj->ktype = ktype;
346 return;
347
348 error:
349 printk(KERN_ERR "kobject (%p): %s
", kobj, err_str);
350 dump_stack();
351 }
352 EXPORT_SYMBOL(kobject_init);
// kobject_init_internal 一些属性的初始化
187 static void kobject_init_internal(struct kobject *kobj)
188 {
189 if (!kobj)
190 return;
191 kref_init(&kobj->kref); // 设置计数为1
192 INIT_LIST_HEAD(&kobj->entry);
193 kobj->state_in_sysfs = 0;
194 kobj->state_add_uevent_sent = 0;
195 kobj->state_remove_uevent_sent = 0;
196 kobj->state_initialized = 1; // 设置初始化状态
// drivers/base/bus.c
// 这里先将 两个变量作为全局变量
25 /* /sys/devices/system */
26 static struct kset *system_kset;
178 static struct kset *bus_kset;
// 入口函数
1278 int __init buses_init(void)
1279 { // kset 创建和添加 , 名字为"bus" "bus事件操作" “父project 为空”
1280 bus_kset = kset_create_and_add("bus", &bus_uevent_ops, NULL);
1281 if (!bus_kset)
1282 return -ENOMEM;
1283
1284 system_kset = kset_create_and_add("system", NULL, &devices_kset->kobj);
1285 if (!system_kset)
1286 return -ENOMEM;
1287
1288 return 0;
1289 }
// kset_create_and_add
// 头文件 include/linux/kobject.h
178 extern struct kset * __must_check kset_create_and_add(const char *name,
179 const struct kset_uevent_ops *u,
180 struct kobject *parent_kobj);
// 源代码 lib/kobject.c
936 struct kset *kset_create_and_add(const char *name,
937 const struct kset_uevent_ops *uevent_ops,
938 struct kobject *parent_kobj)
939 {
940 struct kset *kset;
941 int error;
942 // 名字为"bus" ，申请一段空间并初始化相关kset 属性
943 kset = kset_create(name, uevent_ops, parent_kobj);
944 if (!kset)
945 return NULL;
946 error = kset_register(kset); // 注册
947 if (error) {
948 kfree(kset);
949 return NULL;
950 }
951 return kset;
952 }
// lib/kobject.c
// kset_register
809 int kset_register(struct kset *k)
810 {
811 int err;
812
813 if (!k)
814 return -EINVAL;
815 // 初始化
816 kset_init(k);
817 err = kobject_add_internal(&k->kobj); // 接下
818 if (err)
819 return err;
820 kobject_uevent(&k->kobj, KOBJ_ADD);
821 return 0;
822 }
823 EXPORT_SYMBOL(kset_register);
// kset 初始化
767 void kset_init(struct kset *k)
768 { // 这个在上面已经跟过了
// 最主要是初始化了 state_initialized = 1
769 kobject_init_internal(&k->kobj);
770 INIT_LIST_HEAD(&k->list); // 设置为链表头
771 spin_lock_init(&k->list_lock);
772 }
// kobject_add_internal
200 static int kobject_add_internal(struct kobject *kobj)
201 {
202 int error = 0;
203 struct kobject *parent;
204
205 if (!kobj)
206 return -ENOENT;
207
208 if (!kobj->name || !kobj->name[0]) {
209 WARN(1, "kobject: (%p): attempted to be registered with empty "
210 "name!
", kobj);
211 return -EINVAL;
212 }
213
214 parent = kobject_get(kobj->parent);
215
216 /* join kset if set, use it as parent if we do not already have one */
217 if (kobj->kset) {
218 if (!parent)
219 parent = kobject_get(&kobj->kset->kobj);
220 kobj_kset_join(kobj);
221 kobj->parent = parent;
222 }