struct kobject { const char *name; /* 名字，对应sysfs下的一个目录 */ struct list_head entry; /* kobject中插入的 list_head结构，用于构造双向链表 */ struct kobject *parent; /* 指向当前kobject父对象的指针，体现在sys中就是包含当前kobject对象的目录对象 */ struct kset *kset; /* 当前kobject对象所属的集合 */ struct kobj_type *ktype; /* 当前kobject对象的类型 */ struct kernfs_node *sd; /* VFS文件系统的目录项，是设备和文件之间的桥梁，sysfs中的符号链接是通过kernfs_node内的联合体实现的 */ struct kref kref; /* kobject的引用计数，当计数为0时，回调之前注册的release方法释放该对象 */#ifdef CONFIG_DEBUG_KOBJECT_RELEASE struct delayed_work release;#endif unsigned int state_initialized:1; /* 初始化标志位，初始化时被置位 */ unsigned int state_in_sysfs:1; /* kobject在sysfs中的状态，在目录中创建则为1，否则为0 */ unsigned int state_add_uevent_sent:1; /* 添加设备的uevent事件是否发送标志，添加设备时向用户空间发送uevent事件，请求新增设备 */ unsigned int state_remove_uevent_sent:1; /* 删除设备的uevent事件是否发送标志，删除设备时向用户空间发送uevent事件，请求卸载设备 */ unsigned int uevent_suppress:1; /* 是否忽略上报（不上报uevent） */};

struct kset { struct list_head list; /* 包含在kset内的所有kobject构成一个双向链表 */ spinlock_t list_lock; struct kobject kobj; /* 归属于该kset的所有的kobject的共有parent */ const struct kset_uevent_ops *uevent_ops; /* kset的uevent操作函数集，当kset中的kobject有状态变化时，会回调这个函数集，以便kset添加新的环境变量或过滤某些uevent，如果一个kobject不属于任何kset时，是不允许发送uevent的 */} __randomize_layout;

struct kobj_type { void (*release)(struct kobject *kobj); /* 释放kobject对象的接口，有点类似面向对象中的析构 */ const struct sysfs_ops *sysfs_ops; /* 操作kobject的方法集 */ struct attribute **default_attrs; const struct kobj_ns_type_operations *(*child_ns_type)(struct kobject *kobj); const void *(*namespace)(struct kobject *kobj);};
struct sysfs_ops { /* kobject操作函数集 */ ssize_t (*show)(struct kobject *, struct attribute *, char *); ssize_t (*store)(struct kobject *, struct attribute *, const char *, size_t);};
/* 所谓的attribute就是内核空间和用户空间进行信息交互的一种方法，例如某个driver定义了一个变量，却希望用户空间程序可以修改该变量，以控制driver的行为，那么可以将该变量以sysfs attribute的形式开放出来 */struct attribute { const char *name; umode_t mode;#ifdef CONFIG_DEBUG_LOCK_ALLOC bool ignore_lockdep:1; struct lock_class_key *key; struct lock_class_key skey;#endif};

#include <linux/kernel.h>#include <linux/module.h>#include <linux/slab.h>#include <linux/kobject.h>
//自定义一个结构，包含了struct kobject子结构struct test_kobj { int value; struct kobject kobj;};
//自定义个属性结构体，包含了struct attribute结构struct test_kobj_attribute { struct attribute attr; ssize_t (*show)(struct test_kobj *obj, struct test_kobj_attribute *attr, char *buf); ssize_t (*store)(struct test_kobj *obj, struct test_kobj_attribute *attr, const char *buf, size_t count);};
//声明一个全局结构用于测试struct test_kobj *obj;
//用于初始化sysfs_ops中的函数指针static ssize_t test_kobj_attr_show(struct kobject *kobj, struct attribute *attr, char *buf){ struct test_kobj_attribute *test_kobj_attr; ssize_t ret = -EIO;
 test_kobj_attr = container_of(attr, struct test_kobj_attribute, attr);  //回调到具体的实现函数 if (test_kobj_attr->show) ret = test_kobj_attr->show(container_of(kobj, struct test_kobj, kobj), test_kobj_attr, buf);  return ret;}
//用于初始化sysfs_ops中的函数指针static ssize_t test_kobj_attr_store(struct kobject *kobj, struct attribute *attr, const char *buf, size_t count){ struct test_kobj_attribute *test_kobj_attr; ssize_t ret = -EIO;
 test_kobj_attr = container_of(attr, struct test_kobj_attribute, attr);  //回调到具体的实现函数 if (test_kobj_attr->store) ret = test_kobj_attr->store(container_of(kobj, struct test_kobj, kobj), test_kobj_attr, buf, count);  return ret;}
//用于初始化kobj_ktypeconst struct sysfs_ops test_kobj_sysfs_ops = { .show = test_kobj_attr_show, .store = test_kobj_attr_store,};
//用于初始化kobj_ktype，最终用于释放kobjectvoid obj_release(struct kobject *kobj){ struct test_kobj *obj = container_of(kobj, struct test_kobj, kobj);
 printk(KERN_INFO "test kobject release %s\n", kobject_name(&obj->kobj));  kfree(obj);}
//定义kobj_ktype，用于指定kobject的类型，初始化的时候使用static struct kobj_type test_kobj_ktype = { .release = obj_release, .sysfs_ops = &test_kobj_sysfs_ops,};
//show函数的具体实现ssize_t name_show(struct test_kobj *obj, struct test_kobj_attribute *attr, char *buffer){ return sprintf(buffer, "%s\n", kobject_name(&obj->kobj));}
//show函数的具体实现ssize_t value_show(struct test_kobj *obj, struct test_kobj_attribute *attr, char *buffer){ return sprintf(buffer, "%d\n", obj->value);}
//store函数的具体实现ssize_t value_store(struct test_kobj *obj, struct test_kobj_attribute *attr, const char *buffer, size_t size){ sscanf(buffer, "%d", &obj->value);
 return size;}
//定义属性，最终注册进sysfs系统struct test_kobj_attribute name_attribute = __ATTR(name, 0664, name_show, NULL);struct test_kobj_attribute value_attribute = __ATTR(value, 0664, value_show, value_store);struct attribute *test_kobj_attrs[] = { &name_attribute.attr, &value_attribute.attr, NULL,};
//定义组struct attribute_group test_kobj_group = { .name = "test_kobj_group", .attrs = test_kobj_attrs,};
//模块初始化函数static int __init test_kobj_init(void){ int retval; printk(KERN_INFO "test_kobj_init\n"); obj = kmalloc(sizeof(struct test_kobj), GFP_KERNEL); if (!obj) { return -ENOMEM; }  obj->value = 1; memset(&obj->kobj, 0, sizeof(struct kobject)); //添加进sysfs系统 kobject_init_and_add(&obj->kobj, &test_kobj_ktype, NULL, "test_kobj");
 //在sys文件夹下创建文件 retval = sysfs_create_files(&obj->kobj, (const struct attribute **)test_kobj_attrs); if (retval) { kobject_put(&obj->kobj); return retval; }  //在sys文件夹下创建group retval = sysfs_create_group(&obj->kobj, &test_kobj_group); if (retval) { kobject_put(&obj->kobj); return retval; }  return 0;}
//模块清理函数static void __exit test_kobj_exit(void){ printk(KERN_INFO "test_kobj_exit\n");
 kobject_del(&obj->kobj); kobject_put(&obj->kobj);  return;}
module_init(test_kobj_init);module_exit(test_kobj_exit);
MODULE_AUTHOR("LoyenWang");MODULE_LICENSE("GPL");

ifneq ($(KERNELRELEASE),)obj-m:=test_kobject.oelseKERDIR := /lib/modules/$(shell uname -r)/buildPWD:=$(shell pwd)all: make -C $(KERDIR) M=$(PWD) modulesclean: rm -f *.ko *.o *.symvers *.cmd *.cmd.o modules.* *.mod.cendif