關於Linux設備模型kobject，kset，ktype

一、sysfs文件系統下的每個目錄對應於一個kobj，kset是kobj的封裝，內嵌了一個kobj，其代表kset自身，ktype代表屬性操作集，但由於通用性，因此把ktype單獨剝離出來，kobj，kset，ktype成為了各個驅動模型最底層的關聯元素，並由此形成了sys下的各種拓撲結構。

二、關於kobject

首先看一下kobject的原型

[cpp]

1. struct kobject {
2. const char *name; //名字
3. struct list_head entry; //連接到kset建立層次結構
4. struct kobject *parent; //指向父節點，面向對象的層次架構
5. struct kset *kset;
6. struct kobj_type *ktype; //屬性文件
7. struct sysfs_dirent *sd;
8. struct kref kref; //引用計數
9. unsigned int state_initialized:1; //初始化狀態...
10. unsigned int state_in_sysfs:1;
11. unsigned int state_add_uevent_sent:1;
12. unsigned int state_remove_uevent_sent:1;
13. unsigned int uevent_suppress:1;
14. };

分析一下kobject的初始化過程

初始化函數為

[cpp]

1. ---int kobject_init_and_add(struct kobject *kobj, struct kobj_type *ktype, //參數為kobject和屬性結構體
2. struct kobject *parent, const char *fmt, ...)
3. {
4. va_list args;
5. int retval;
6. kobject_init(kobj, ktype);
7. va_start(args, fmt);
8. retval = kobject_add_varg(kobj, parent, fmt, args);
9. va_end(args);
10. return retval;
11. }
12. ---void kobject_init(struct kobject *kobj, struct kobj_type *ktype)
13. {
14. char *err_str;
15. if (!kobj) { //kobj為NULL錯誤退出
16. err_str = "invalid kobject pointer!";
17. goto error;
18. }
19. if (!ktype) { //ktype為NULL錯誤退出
20. err_str = "must have a ktype to be initialized properly!/n";
21. goto error;
22. }
23. if (kobj->state_initialized) { //如果初始化狀態為1報錯
24. /* do not error out as sometimes we can recover */
25. printk(KERN_ERR "kobject (%p): tried to init an initialized "
26. "object, something is seriously wrong./n", kobj);
27. dump_stack();
28. }
29. kobject_init_internal(kobj); //初始化kobj
30. kobj->ktype = ktype; //關聯obj和ktype
31. return;
32. error:
33. printk(KERN_ERR "kobject (%p): %s/n", kobj, err_str);
34. dump_stack();
35. }
36. -------static void kobject_init_internal(struct kobject *kobj)
37. {
38. if (!kobj)
39. return;
40. kref_init(&kobj->kref); //計數變成1
41. INIT_LIST_HEAD(&kobj->entry); //都指向自己，prev和next
42. kobj->state_in_sysfs = 0;
43. kobj->state_add_uevent_sent = 0;
44. kobj->state_remove_uevent_sent = 0;
45. kobj->state_initialized = 1;
46. }
47. -------static int kobject_add_varg(struct kobject *kobj, struct kobject *parent,
48. const char *fmt, va_list vargs)
49. {
50. int retval;
51. retval = kobject_set_name_vargs(kobj, fmt, vargs); //設置名字，名字中不能有“/”
52. if (retval) {
53. printk(KERN_ERR "kobject: can not set name properly!/n");
54. return retval;
55. }
56. kobj->parent = parent; //設置parent，其父節點
57. return kobject_add_internal(kobj);
58. }
59. ----static int kobject_add_internal(struct kobject *kobj)
60. {
61. int error = 0;
62. struct kobject *parent;
63. if (!kobj)
64. return -ENOENT;
65. if (!kobj->name || !kobj->name[0]) { //名字不能為空
66. WARN(1, "kobject: (%p): attempted to be registered with empty "
67. "name!/n", kobj);
68. return -EINVAL;
69. }
70. parent = kobject_get(kobj->parent); //如果parent為真，則增加kobj->kref計數，也就是父節點的引用計數
71. /* join kset if set, use it as parent if we do not already have one */
72. if (kobj->kset) {
73. if (!parent)
74. parent = kobject_get(&kobj->kset->kobj); //如果kobj-parent父節點為NULL那麼就用kobj->kset->kobj
75. // 作其父節點，並增加其引用計數
76. kobj_kset_join(kobj); //把kobj的entry成員添加到kobj->kset>list的尾部，現在的層次就是
77. kobj->parent = parent; //kobj->kset->list指向kobj->parent
78. } // ->parent 指向kset->kobj
79. pr_debug("kobject: '%s' (%p): %s: parent: '%s', set: '%s'/n",
80. kobject_name(kobj), kobj, __func__,
81. parent ? kobject_name(parent) : "<NULL>",
82. kobj->kset ? kobject_name(&kobj->kset->kobj) : "<NULL>");
83. error = create_dir(kobj); //利用kobj創建目錄和屬性文件，其中會判斷，如果parent為NULL那麼就在sysfs_root下創建
84. if (error) {
85. kobj_kset_leave(kobj);
86. kobject_put(parent);
87. kobj->parent = NULL;
88. /* be noisy on error issues */
89. if (error == -EEXIST)
90. printk(KERN_ERR "%s failed for %s with "
91. "-EEXIST, don't try to register things with "
92. "the same name in the same directory./n",
93. __func__, kobject_name(kobj));
94. else
95. printk(KERN_ERR "%s failed for %s (%d)/n",
96. __func__, kobject_name(kobj), error);
97. dump_stack();
98. } else
99. kobj->state_in_sysfs = 1;
100. return error;
101. }
102. ---static int create_dir(struct kobject *kobj)
103. {
104. int error = 0;
105. if (kobject_name(kobj)) {
106. error = sysfs_create_dir(kobj); //創建目錄
107. if (!error) {
108. error = populate_dir(kobj); //創建屬性文件
109. if (error)
110. sysfs_remove_dir(kobj);
111. }
112. }
113. return error;
114. }