ret = dev_attr->show(dev, buf);
ret = dev_attr->show(dev, dev_attr, buf);
dev_attr_show(struct kobject * kobj, struct attribute * attr, char * buf){	struct device_attribute * dev_attr = to_dev_attr(attr);	struct device * dev = to_dev(kobj);	ssize_t ret = -EIO;	if (dev_attr->show)		ret = dev_attr->show(dev, buf);	return ret;}