I know that device numbers change, but bus/port numbers are stable and reflect the physical layout of the hubs and devices. I relied for years on these port numbers to identify specific (otherwise identical) devices. Searching the list (I am now subscribed) and the web did not yield an answer. For example, I have two TEMPer temperature sensor devices attached. They are both plugged into a 4-port USB3 hub. They are on ports 3 and 4. Port 2 is unused and port 1 has a bluetooth radio attached. I also have 5 dvb usb tuners which stayed in their old positions. Until now (fedora 34, last on 5.12.17-300.fc34.x86_64), I would see this: $ lsusb Bus 001 Device 013: ID 0c45:7401 Microdia TEMPer Temperature Sensor Bus 001 Device 025: ID 0c45:7401 Microdia TEMPer Temperature Sensor $ lsusb -t /: Bus 02.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/10p, 10000M |__ Port 4: Dev 2, If 0, Class=Hub, Driver=hub/4p, 5000M |__ Port 4: Dev 4, If 0, Class=Hub, Driver=hub/4p, 5000M |__ Port 5: Dev 3, If 0, Class=Hub, Driver=hub/4p, 5000M /: Bus 01.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/16p, 480M |__ Port 2: Dev 26, If 0, Class=Hub, Driver=hub/4p, 480M |__ Port 2: Dev 27, If 1, Class=Human Interface Device, Driver=usbhid, 12M |__ Port 2: Dev 27, If 0, Class=Human Interface Device, Driver=usbhid, 12M |__ Port 4: Dev 3, If 0, Class=Hub, Driver=hub/4p, 480M |__ Port 3: Dev 10, If 1, Class=Vendor Specific Class, Driver=, 480M |__ Port 3: Dev 10, If 0, Class=Vendor Specific Class, Driver=dvb_usb_rtl28xxu, 480M |__ Port 1: Dev 6, If 0, Class=Vendor Specific Class, Driver=dvb_usb_rtl28xxu, 480M |__ Port 1: Dev 6, If 1, Class=Vendor Specific Class, Driver=, 480M |__ Port 4: Dev 12, If 0, Class=Hub, Driver=hub/4p, 480M |__ Port 3: Dev 15, If 0, Class=Printer, Driver=usblp, 12M |__ Port 1: Dev 14, If 1, Class=Vendor Specific Class, Driver=, 480M |__ Port 1: Dev 14, If 0, Class=Vendor Specific Class, Driver=dvb_usb_rtl28xxu, 480M |__ Port 4: Dev 16, If 0, Class=Vendor Specific Class, Driver=dvb_usb_rtl28xxu, 480M |__ Port 4: Dev 16, If 1, Class=Vendor Specific Class, Driver=, 480M |__ Port 2: Dev 8, If 0, Class=Vendor Specific Class, Driver=dvb_usb_rtl28xxu, 480M |__ Port 2: Dev 8, If 1, Class=Vendor Specific Class, Driver=, 480M |__ Port 5: Dev 5, If 0, Class=Hub, Driver=hub/4p, 480M |__ Port 1: Dev 20, If 0, Class=Wireless, Driver=btusb, 12M |__ Port 1: Dev 20, If 1, Class=Wireless, Driver=btusb, 12M |__ Port 3: Dev 25, If 0, Class=Human Interface Device, Driver=, 1.5M <<<<< |__ Port 3: Dev 25, If 1, Class=Human Interface Device, Driver=, 1.5M <<<<< |__ Port 4: Dev 13, If 0, Class=Human Interface Device, Driver=, 1.5M <<<<< |__ Port 4: Dev 13, If 1, Class=Human Interface Device, Driver=, 1.5M <<<<< |__ Port 6: Dev 19, If 0, Class=Human Interface Device, Driver=usbfs, 1.5M The TEMPer devices show on Bus 01 as was always: Port 5.Port 3 (Dev 11) Port 5.Port 4 (Dev 13) After rebooting the newly installed kernel 5.13.4-200.fc34.x86_64 I get: $ lsusb Bus 001 Device 012: ID 0c45:7401 Microdia TEMPer Temperature Sensor Bus 001 Device 003: ID 0c45:7401 Microdia TEMPer Temperature Sensor $ lsusb -t /: Bus 02.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/10p, 10000M |__ Port 4: Dev 2, If 0, Class=Hub, Driver=hub/4p, 5000M |__ Port 4: Dev 4, If 0, Class=Hub, Driver=hub/4p, 5000M |__ Port 5: Dev 3, If 0, Class=Hub, Driver=hub/4p, 5000M /: Bus 01.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/16p, 480M |__ Port 2: Dev 2, If 0, Class=Hub, Driver=hub/4p, 480M |__ Port 2: Dev 4, If 1, Class=Human Interface Device, Driver=usbhid, 12M |__ Port 2: Dev 4, If 0, Class=Human Interface Device, Driver=usbhid, 12M |__ Port 3: Dev 3, If 0, Class=Human Interface Device, Driver=, 1.5M <<<<< |__ Port 3: Dev 3, If 1, Class=Human Interface Device, Driver=, 1.5M <<<<< |__ Port 4: Dev 5, If 0, Class=Hub, Driver=hub/4p, 480M |__ Port 3: Dev 11, If 1, Class=Vendor Specific Class, Driver=, 480M |__ Port 3: Dev 11, If 0, Class=Vendor Specific Class, Driver=dvb_usb_rtl28xxu, 480M |__ Port 1: Dev 7, If 0, Class=Vendor Specific Class, Driver=dvb_usb_rtl28xxu, 480M |__ Port 1: Dev 7, If 1, Class=Vendor Specific Class, Driver=, 480M |__ Port 4: Dev 13, If 0, Class=Hub, Driver=hub/4p, 480M |__ Port 3: Dev 15, If 0, Class=Printer, Driver=usblp, 12M |__ Port 1: Dev 14, If 1, Class=Vendor Specific Class, Driver=, 480M |__ Port 1: Dev 14, If 0, Class=Vendor Specific Class, Driver=dvb_usb_rtl28xxu, 480M |__ Port 4: Dev 16, If 0, Class=Vendor Specific Class, Driver=dvb_usb_rtl28xxu, 480M |__ Port 4: Dev 16, If 1, Class=Vendor Specific Class, Driver=, 480M |__ Port 2: Dev 9, If 0, Class=Vendor Specific Class, Driver=dvb_usb_rtl28xxu, 480M |__ Port 2: Dev 9, If 1, Class=Vendor Specific Class, Driver=, 480M |__ Port 5: Dev 6, If 0, Class=Hub, Driver=hub/4p, 480M |__ Port 1: Dev 10, If 0, Class=Wireless, Driver=btusb, 12M |__ Port 1: Dev 10, If 1, Class=Wireless, Driver=btusb, 12M |__ Port 3: Dev 12, If 0, Class=Human Interface Device, Driver=, 1.5M <<<<< |__ Port 3: Dev 12, If 1, Class=Human Interface Device, Driver=, 1.5M <<<<< |__ Port 6: Dev 18, If 0, Class=Human Interface Device, Driver=usbfs, 1.5M One can see that the TEMPer devices are now showing on Bus 01 but in separate positions: Port 3 (Dev 3) new position Port 5.Port 3 (Dev 12) old position This, naturally, confuses my script that collects the data from these sensors (I use temper-poll). Is this an intentional change? If so then what is the way to stably disambiguate usb devices (there is no s/n available)? If no change was expected then does this reflect a possible hwr problem here? -- Eyal Lebedinsky (eyal@xxxxxxxxxxxxxx)