Description of problem: Currently when assigning a host USB device to a guest you must specify the bus + device numbers, or using a vendor+product ID pair. Both of these approaches are flawed in their own way: * Device numbers are not stable. Every time you plug+unplug the device the device number is incremented by one. So effectively the device number is only useful with transient guests - if using in a persistent guest config it will likely fail in the future * Vendor + product ID pairs are not unique if two or more identical devices are attached. Fortunately QEMU does now provide an alternative which is to address the host device based on a bus + port number pair. This is guaranteed unique and stable for as long as the device is plugged into the same physical port. This is clearly the most useful addressing method for persistent guests and libvirt should support it There was a patch for this sent upstream but we dropped the ball & never reviewed or merged it https://www.redhat.com/archives/libvir-list/2016-July/msg00127.html
After evaluating this issue, there are no plans to address it further or fix it in an upcoming release. Therefore, it is being closed. If plans change such that this issue will be fixed in an upcoming release, then the bug can be reopened.