kobject_add-优快云博客

本文链接：https://blog.youkuaiyun.com/wmzjzwlzs/article/details/123658475

本文介绍了Linux内核中kobject结构及其作用，详细讲述了kobject_add函数的工作流程，包括对象初始化、名称设置、sysfs目录创建及错误处理。重点在于kobject如何加入kset和创建sysfs目录的过程。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

struct kobject {
   const char       *name;
   struct list_head   entry;
   struct kobject       *parent;
   struct kset       *kset;
   struct kobj_type   *ktype;
   struct kernfs_node   *sd; /* sysfs directory entry */
   struct kref       kref;
#ifdef CONFIG_DEBUG_KOBJECT_RELEASE
   struct delayed_work   release;
#endif
   unsigned int state_initialized:1;
   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;
};

int kobject_add(struct kobject *kobj, struct kobject *parent,
       const char *fmt, ...)
{
   va_list args;
   int retval;

if (!kobj)
return -EINVAL;

   if (!kobj->state_initialized) {
       printk(KERN_ERR "kobject '%s' (%p): tried to add an "
               "uninitialized object, something is seriously wrong.\n",
               kobject_name(kobj), kobj);
       dump_stack();
       return -EINVAL;
   }
   va_start(args, fmt);
   retval = kobject_add_varg(kobj, parent, fmt, args);
   va_end(args);

return retval;
}

static __printf(3, 0) 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);
   if (retval) {
       printk(KERN_ERR "kobject: can not set name properly!\n");
       return retval;
   }
   kobj->parent = parent;
   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]) {
       WARN(1, "kobject: (%p): attempted to be registered with empty "
           "name!\n", kobj);
       return -EINVAL;
   }

parent = kobject_get(kobj->parent);

   /* 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);
       kobj_kset_join(kobj);
       kobj->parent = parent;
   }

   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);
   if (error) {
       kobj_kset_leave(kobj);
       kobject_put(parent);
       kobj->parent = NULL;

       /* be noisy on error issues */
       if (error == -EEXIST)
           pr_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
           pr_err("%s failed for %s (error: %d parent: %s)\n",
                   __func__, kobject_name(kobj), error,
                   parent ? kobject_name(parent) : "'none'");
   } else
       kobj->state_in_sysfs = 1;

return error;
}

static int create_dir(struct kobject *kobj)
{
const struct kobj_ns_type_operations *ops;
int error;

   error = sysfs_create_dir_ns(kobj, kobject_namespace(kobj));
   if (error)
       return error;

   error = populate_dir(kobj);
   if (error) {
       sysfs_remove_dir(kobj);
       return error;
   }

   /*
   * @kobj->sd may be deleted by an ancestor going away. Hold an
   * extra reference so that it stays until @kobj is gone.
   */
   sysfs_get(kobj->sd);

   /*
   * If @kobj has ns_ops, its children need to be filtered based on
   * their namespace tags. Enable namespace support on @kobj->sd.
   */
   ops = kobj_child_ns_ops(kobj);
   if (ops) {
       BUG_ON(ops->type <= KOBJ_NS_TYPE_NONE);
       BUG_ON(ops->type >= KOBJ_NS_TYPES);
       BUG_ON(!kobj_ns_type_registered(ops->type));

sysfs_enable_ns(kobj->sd);
}

return 0;
}

int sysfs_create_dir_ns(struct kobject *kobj, const void *ns)
{
struct kernfs_node *parent, *kn;

BUG_ON(!kobj);

   if (kobj->parent)
       parent = kobj->parent->sd;
   else
       parent = sysfs_root_kn;

if (!parent)
return -ENOENT;

   kn = kernfs_create_dir_ns(parent, kobject_name(kobj),
                  S_IRWXU | S_IRUGO | S_IXUGO, kobj, ns);
   if (IS_ERR(kn)) {
       if (PTR_ERR(kn) == -EEXIST)
           sysfs_warn_dup(parent, kobject_name(kobj));
       return PTR_ERR(kn);
   }

kobj->sd = kn;
return 0;
}

int __init sysfs_init(void)
{
int err;

   sysfs_root = kernfs_create_root(NULL, KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK,
                   NULL);
   if (IS_ERR(sysfs_root))
       return PTR_ERR(sysfs_root);

sysfs_root_kn = sysfs_root->kn; ///sys

   err = register_filesystem(&sysfs_fs_type);
   if (err) {
       kernfs_destroy_root(sysfs_root);
       return err;
   }

return 0;
}