From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CEFD5C433E6 for ; Wed, 13 Jan 2021 18:55:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7023D2250E for ; Wed, 13 Jan 2021 18:55:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728395AbhAMSzo (ORCPT ); Wed, 13 Jan 2021 13:55:44 -0500 Received: from mail.kernel.org ([198.145.29.99]:44684 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728328AbhAMSzn (ORCPT ); Wed, 13 Jan 2021 13:55:43 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 644E32222B; Wed, 13 Jan 2021 18:55:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1610564102; bh=yuHsL79Rd3202Hi/UJQF2BDz8BRxCYQuw84DSpJYcDM=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=UsUMq6YOXYcOu6I4d3KphnjPuEzQGMmMHeCifzbpDARasRxk4mAo64ZTqQA4Ml6FR EphaTP+Ij6RI0+FrIywMXGIbbx4ucGUg07K64nOzp4LwIJz5dJreO8qH8UR+GXttTQ CwdPgg0ZdTs6wXD52cZNNuUy+XUziKZf37i9CZcAVQKi7QeaP+SvM6PpD7ey4o1B7E KHktYPP4zp/gqzP3bTIRDfUVaWQOBSRSOmUoMrAH8iONdbDdSbSg7ohmDVXTfCqEH+ HU3xKBwzcKJX/DWX5NYJzGt/5fH6JDLoq55Hz+lyx08LfYYliM/C22f8OwT9Ge9q1X Qe5l2AYkCmWkw== Date: Wed, 13 Jan 2021 12:55:00 -0600 From: Bjorn Helgaas To: Niklas Schnelle Cc: linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, Pierre Morel , Peter Oberparleiter , Viktor Mihajlovski Subject: Re: [RFC 1/1] s390/pci: expose UID checking state in sysfs Message-ID: <20210113185500.GA1918216@bjorn-Precision-5520> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4f5013a1-3dde-1633-a0cc-591fc439e29d@linux.ibm.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 13, 2021 at 08:47:58AM +0100, Niklas Schnelle wrote: > On 1/12/21 10:50 PM, Bjorn Helgaas wrote: > > On Mon, Jan 11, 2021 at 10:38:57AM +0100, Niklas Schnelle wrote: > >> We use the UID of a zPCI adapter, or the UID of the function zero if > >> there are multiple functions in an adapter, as PCI domain if and only if > >> UID Checking is turned on. > >> Otherwise we automatically generate domains as devices appear. > >> > >> The state of UID Checking is thus essential to know if the PCI domain > >> will be stable, yet currently there is no way to access this information > >> from userspace. > >> So let's solve this by showing the state of UID checking as a sysfs > >> attribute in /sys/bus/pci/uid_checking > >> +/* Global zPCI attributes */ > >> +static ssize_t uid_checking_show(struct kobject *kobj, > >> + struct kobj_attribute *attr, char *buf) > >> +{ > >> + return sprintf(buf, "%i\n", zpci_unique_uid); > >> +} > >> + > >> +static struct kobj_attribute sys_zpci_uid_checking_attr = > >> + __ATTR(uid_checking, 0444, uid_checking_show, NULL); > > > > Use DEVICE_ATTR_RO instead of __ATTR. > > It's my understanding that DEVICE_ATTR_* is only for > per device attributes. This one is global for the entire > Z PCI. I just tried with BUS_ATTR_RO instead > and that works but only if I put the attribute at > /sys/bus/pci/uid_checking instead of with a zpci > subfolder. This path would work for us too, we > currently don't have any other global attributes > that we are planning to expose but those could of > course come up in the future. Ah, I missed the fact that this is a kobj_attribute, not a device_attribute. Maybe KERNEL_ATTR_RO()? Very few uses so far, but seems like it might fit? Bjorn