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一、sysfs文件系统下的每个目录对应于一个kobj，kset是kobj的封装，内嵌了一个kobj，其代表kset自身，ktype代表属性操作集，但由于通用性，因此把ktype单独剥离出来，kobj，kset，ktype成为了各个驱动模型最底层的关联元素，并由此形成了sys下的各种拓扑结构。

二、关于kobject

      首先看一下kobject的原型

            struct kobject { const char *name; //名字 struct list_head entry; //连接到kset建立层次结构 struct kobject *parent; //指向父节点，面向对象的层次架构 struct kset *kset; struct kobj_type *ktype; //属性文件 struct sysfs_dirent *sd; struct kref kref; //引用计数 unsigned int state_initialized:1; //初始化状态... unsigned int state_in_sysfs:1; unsigned int state_add_uevent_sent:1; unsigned int state_remove_uevent_sent:1; unsigned int uevent_suppress:1; };

   分析一下kobject的初始化过程

   初始化函数为

           ---int kobject_init_and_add(struct kobject *kobj, struct kobj_type *ktype, //参数为kobject和属性结构体 struct kobject *parent, const char *fmt, ...) { va_list args; int retval; kobject_init(kobj, ktype); va_start(args, fmt); retval = kobject_add_varg(kobj, parent, fmt, args); va_end(args); return retval; } ---void kobject_init(struct kobject *kobj, struct kobj_type *ktype) { char *err_str; if (!kobj) { //kobj为NULL错误退出 err_str = "invalid kobject pointer!"; goto error; } if (!ktype) { //ktype为NULL错误退出 err_str = "must have a ktype to be initialized properly!/n"; goto error; } if (kobj->state_initialized) { //如果初始化状态为1报错 /* do not error out as sometimes we can recover */ printk(KERN_ERR "kobject (%p): tried to init an initialized " "object, something is seriously wrong./n", kobj); dump_stack(); } kobject_init_internal(kobj); //初始化kobj kobj->ktype = ktype; //关联obj和ktype return; error: printk(KERN_ERR "kobject (%p): %s/n", kobj, err_str); dump_stack(); } -------static void kobject_init_internal(struct kobject *kobj) { if (!kobj) return; kref_init(&kobj->kref); //计数变成1 INIT_LIST_HEAD(&kobj->entry); //都指向自己，prev和next kobj->state_in_sysfs = 0; kobj->state_add_uevent_sent = 0; kobj->state_remove_uevent_sent = 0; kobj->state_initialized = 1; } -------static int kobject_add_varg(struct kobject *kobj, struct kobject *parent, const char *fmt, va_list vargs) { int retval; retval = kobject_set_name_vargs(kobj, fmt, vargs); //设置名字，名字中不能有“/” if (retval) { printk(KERN_ERR "kobject: can not set name properly!/n"); return retval; } kobj->parent = parent; //设置parent，其父节点 return kobject_add_internal(kobj); } ----static int kobject_add_internal(struct kobject *kobj) { int error = 0; struct kobject *parent; if (!kobj) return -ENOENT; if (!kobj->name || !kobj->name[0]) { //名字不能为空 WARN(1, "kobject: (%p): attempted to be registered with empty " "name!/n", kobj); return -EINVAL; } parent = kobject_get(kobj->parent); //如果parent为真，则增加kobj->kref计数，也就是父节点的引用计数 /* join kset if set, use it as parent if we do not already have one */ if (kobj->kset) { if (!parent) parent = kobject_get(&kobj->kset->kobj); //如果kobj-parent父节点为NULL那么就用kobj->kset->kobj // 作其父节点，并增加其引用计数 kobj_kset_join(kobj); //把kobj的entry成员添加到kobj->kset>list的尾部，现在的层次就是 kobj->parent = parent; //kobj->kset->list指向kobj->parent } // ->parent 指向kset->kobj pr_debug("kobject: '%s' (%p): %s: parent: '%s', set: '%s'/n", kobject_name(kobj), kobj, __func__, parent ? kobject_name(parent) : "<NULL>", kobj->kset ? kobject_name(&kobj->kset->kobj) : "<NULL>"); error = create_dir(kobj); //利用kobj创建目录和属性文件，其中会判断，如果parent为NULL那么就在sysfs_root下创建 if (error) { kobj_kset_leave(kobj); kobject_put(parent); kobj->parent = NULL; /* be noisy on error issues */ if (error == -EEXIST) printk(KERN_ERR "%s failed for %s with " "-EEXIST, don't try to register things with " "the same name in the same directory./n", __func__, kobject_name(kobj)); else printk(KERN_ERR "%s failed for %s (%d)/n", __func__, kobject_name(kobj), error); dump_stack(); } else kobj->state_in_sysfs = 1; return error; } ---static int create_dir(struct kobject *kobj) { int error = 0; if (kobject_name(kobj)) { error = sysfs_create_dir(kobj); //创建目录 if (!error) { error = populate_dir(kobj); //创建属性文件 if (error) sysfs_remove_dir(kobj); } } return error; }

三、关于 kset

      首先看一下kset的原型

          struct kset { struct list_head list; //连接着他下面的kobj成员，与kobj-entry关联 spinlock_t list_lock; struct kobject kobj; //代表kset自己 const struct kset_uevent_ops *uevent_ops; };

       再来看一下kset的初始化操作，kset表现为更高级一点的kobj，其初始化操作仍然是围绕其内部的kobj展开的。

          struct kset *kset_create_and_add(const char *name, const struct kset_uevent_ops *uevent_ops, struct kobject *parent_kobj) { struct kset *kset; int error; kset = kset_create(name, uevent_ops, parent_kobj); //创建kset，关联操作函数和其父节点 if (!kset) return NULL; error = kset_register(kset); if (error) { kfree(kset); return NULL; } return kset; } ---static struct kset *kset_create(const char *name, const struct kset_uevent_ops *uevent_ops, struct kobject *parent_kobj) { struct kset *kset; int retval; kset = kzalloc(sizeof(*kset), GFP_KERNEL); //申请结构体内存 if (!kset) return NULL; retval = kobject_set_name(&kset->kobj, name); //设置名字 if (retval) { kfree(kset); return NULL; } kset->uevent_ops = uevent_ops; //关联操作函数 kset->kobj.parent = parent_kobj; //关联父节点 /* * The kobject of this kset will have a type of kset_ktype and belong to * no kset itself. That way we can properly free it when it is * finished being used. */ kset->kobj.ktype = &kset_ktype; //关联属性文件 kset->kobj.kset = NULL; return kset; } ----int kset_register(struct kset *k) { int err; if (!k) return -EINVAL; kset_init(k); err = kobject_add_internal(&k->kobj); //调用kobj操作函数 if (err) return err; kobject_uevent(&k->kobj, KOBJ_ADD); return 0; } ----void kset_init(struct kset *k) { kobject_init_internal(&k->kobj); //调用kobj操作函数 INIT_LIST_HEAD(&k->list); spin_lock_init(&k->list_lock); }

四、上面给出了kobj，kset的初始化过程，以及相互产生关联的关键点，下面给出整体的一个流程图：