static ssize_t state_store(struct device *dev, struct device_attribute *attr,
			   const char *buf, size_t count)
{
	const int online_type = memhp_online_type_from_str(buf);
	struct memory_block *mem = to_memory_block(dev);
	int ret;

	if (online_type < 0)
		return -EINVAL;

	ret = lock_device_hotplug_sysfs();
	if (ret)
		return ret;

	switch (online_type) {
	case MMOP_ONLINE_KERNEL:
	case MMOP_ONLINE_MOVABLE:
	case MMOP_ONLINE:
		/* mem->online_type is protected by device_hotplug_lock */
		mem->online_type = online_type;
		ret = device_online(&mem->dev);
		break;
	case MMOP_OFFLINE:
		ret = device_offline(&mem->dev);
		break;
	default:
		ret = -EINVAL; /* should never happen */
	}

	unlock_device_hotplug();

	if (ret < 0)
		return ret;
	if (ret)
		return -EINVAL;

	return count;
}
static ssize_t state_store(struct device *dev, struct device_attribute *attr,
			   const char *buf, size_t count)
{
	const int online_type = memhp_online_type_from_str(buf);
	struct memory_block *mem = to_memory_block(dev);
	int ret;

	if (online_type < 0)
		return -EINVAL;

	ret = lock_device_hotplug_sysfs();
	if (ret)
		return ret;

	switch (online_type) {
	case MMOP_ONLINE_KERNEL:
	case MMOP_ONLINE_MOVABLE:
	case MMOP_ONLINE:
		 
		mem->online_type = online_type;
		ret = device_online(&mem->dev);
		break;
	case MMOP_OFFLINE:
		ret = device_offline(&mem->dev);
		break;
	default:
		ret = -EINVAL;  
	}

	unlock_device_hotplug();

	if (ret < 0)
		return ret;
	if (ret)
		return -EINVAL;

	return count;
}