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
[cpp]
- 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
[cpp]
- ---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; }