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Wed, 18 Mar 2026 06:33:08 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.45.242.6]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 619B019560AB; Wed, 18 Mar 2026 06:33:07 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id DE85821E6937; Wed, 18 Mar 2026 07:33:04 +0100 (CET) From: Markus Armbruster To: Alessandro Ratti Cc: Markus Armbruster , qemu-devel@nongnu.org, peter.maydell@linaro.org, berrange@redhat.com, mst@redhat.com, pbonzini@redhat.com Subject: Re: [PATCH v2 2/2] hw/qdev: Remove qdev_get_human_name() In-Reply-To: (Alessandro Ratti's message of "Tue, 17 Mar 2026 22:38:48 +0100") References: <20260311215003.664815-1-alessandro@0x65c.net> <20260311215003.664815-3-alessandro@0x65c.net> <87h5qflyqe.fsf@pond.sub.org> Date: Wed, 18 Mar 2026 07:33:04 +0100 Message-ID: <87bjglsl3z.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Received-SPF: pass client-ip=170.10.129.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -3 X-Spam_score: -0.4 X-Spam_bar: / X-Spam_report: (-0.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.819, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.903, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Alessandro Ratti writes: > On Tue, 17 Mar 2026 at 08:08, Markus Armbruster wrote: >> >> Alessandro Ratti writes: >> >> > Remove qdev_get_human_name() and switch its two callers in >> > hw/block/block.c to qdev_get_printable_name(). >> > >> > qdev_get_printable_name() subsumes qdev_get_human_name(): both >> > return the device ID when set and fall back to the canonical QOM >> > path, but qdev_get_printable_name() also tries the bus-specific >> > device path first, providing more informative output. >> > >> > Narrow the scope of dev_id in blk_check_size_and_read_all() to the >> > blocks where it is actually used. >> > >> > Suggested-by: Peter Maydell >> > Signed-off-by: Alessandro Ratti >> >> This replaces two ways to describe a device to the user by one. Good. >> >> One half of the uses is unchanged. Good. >> >> The other half can now show a bus-specific device path instead of the >> canonical QOM path. This path can be difficult to interpret: we have >> some twenty .get_dev_path() methods, and each of them can format however >> it wants. I need to guess the format to make sense of the value. I'm >> inclined to call this a regression. >> >> To address this, please insert another patch before this one that >> changes >> >> device >> >> to >> >> device >> >> This removes the guesswork, and actually satisfies the claim "more >> informative output". >> > > Will do. I've prototyped this using object_get_typename() on > dev->parent_bus to get the bus type. > > A complication: a few buses (virtio-pci-bus, ufs-bus) delegate > get_dev_path() to their parent unchanged, Like so: static char *ufs_bus_get_dev_path(DeviceState *dev) { BusState *bus = qdev_get_parent_bus(dev); return qdev_get_dev_path(bus->parent); } > so the path format doesn't > match the immediate bus type. .get_dev_path()'s contract: /** * qdev_get_dev_path(): Return the path of a device on its bus * @dev: device to get the path of * * Returns: A newly allocated string containing the dev path of * @dev. The caller must free this with g_free(). * The format of the string depends on the bus; for instance a * PCI device's path will be in the format:: * * Domain:00:Slot.Function:Slot.Function....:Slot.Function * * and a SCSI device's path will be:: * * channel:ID:LUN * * (possibly prefixed by the path of the SCSI controller). * * If @dev is NULL or not on a bus, returns NULL. */ This looks decent at a glance, but it's actually somewhat woolly. > I detect delegation by comparing the > child's path to the parent bus's path, and format as > " on device ". > > Tested with i440fx + virtio-blk + UFS + USB + SCSI: > > PCI device 0000:00:04.0 > virtio-pci-bus on PCI device 0000:00:04.0 > ufs-bus on PCI device 0000:00:04.0 > SCSI device 0000:00:04.0/0:0:0 > usb-bus device 0000:00:03.0/1 > > And with Q35: > > PCIE device 0000:00:04.0 > virtio-pci-bus on PCIE device 0000:00:04.0 > ufs-bus on PCIE device 0000:00:04.0 > SCSI device 0000:00:04.0/0:0:0 > usb-bus device 0000:00:03.0/1 > > If my understanding is correct, VMBus delegates to sysbus which has > no get_dev_path(), so it falls through to the QOM path. > > Note: object_get_typename() gives "PCI" on i440fx and "PCIE" on Q35 > for the same address format. Not sure if that's confusing enough to > warrant normalizing. > >> qdev_get_human_name() is a better name than qdev_get_printable_name(). >> Please consider renaming the function so we keep the better name. >> > > Ack, will rename. > > If my proposal to add " device" prefix sounds solid, > I'll send a v3 with the series restructured as: > > 1. Replace "" with canonical QOM path, clean up comments > 2. Add " device" prefix to bus-specific paths > 3. Consolidate into qdev_get_human_name() > > Thanks for your time and consideration. > > Best regards, > Alessandro