On Fri, Jun 17, 2022 at 10:23:13PM +0800, Zhangfei Gao wrote: > @@ -312,12 +345,20 @@ static ssize_t available_instances_show(struct device > *dev, > char *buf) > { > struct uacce_device *uacce = to_uacce_device(dev); > + ssize_t ret; > > - if (!uacce->ops->get_available_instances) > - return -ENODEV; > + mutex_lock(&uacce_mutex); > + if (!uacce->ops || !uacce->ops->get_available_instances) { Doesn't the sysfs group go away with uacce_remove()? We shouldn't need this check Thanks, Jean