Dear @hippy,Something seems to be disconnecting the Debug Probe. Then it gets reconnected.... time passes
$ sudo dmesg | grep -i usb
[106223.600940] usb 1-2: USB disconnect, device number 8
[106228.518939] usb 1-2: new full-speed USB device number 9 using xhci_hcd
...
[108074.733585] usb 1-2: USB disconnect, device number 9
[109166.166898] usb 1-2: new full-speed USB device number 10 using xhci_hcd
...
[112344.897275] usb 1-2: USB disconnect, device number 10
[112794.105504] usb 1-2: new full-speed USB device number 11 using xhci_hcd
If that's not because you are unplugging it and re-plugging it I have no idea why that is.
Thanks for your response.
it is indeed myself plugging and unplugging the RPi Debug Probe. Or in earlier posts to this thread an RPi Pico.
Tried the following experiment. USB A with USB thumb drive stick.
Outcome this is not solely an RPi device issue it appears to affect other USB devices.
Plugging and unplugging another USB device to the same USB A port on Dell Ubuntu does appear to lead also a to continuous increase in device number. The USB thumb drive stick is plugged in and unplugged the device number is incremented when plugged in and then not decremented when it is unplugged. But this is only visible when a subsequent USB device is plugged in.
Dell Ubuntu host has been powered down and powered up. So the device number (count) is now reset. No USB devices have been plugged in. All the USB devices shown are internal to Dell Ubuntu host.
$ lsusb
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 002: ID 0cf3:e300 Qualcomm Atheros Communications QCA61x4 Bluetooth 4.0
Bus 001 Device 003: ID 138a:0091 Validity Sensors, Inc. VFS7552 Touch Fingerprint Sensor
Bus 001 Device 004: ID 04f3:24a1 Elan Microelectronics Corp. Touchscreen
Bus 001 Device 005: ID 0c45:6713 Microdia Integrated_Webcam_HD
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
$ sudo dmesg | grep -i usb
[ 0.475567] ACPI: bus type USB registered
[ 0.475567] usbcore: registered new interface driver usbfs
[ 0.475567] usbcore: registered new interface driver hub
[ 0.475567] usbcore: registered new device driver usb
[ 1.351634] xhci_hcd 0000:00:14.0: new USB bus registered, assigned bus number 1
[ 1.353462] xhci_hcd 0000:00:14.0: new USB bus registered, assigned bus number 2
[ 1.353465] xhci_hcd 0000:00:14.0: Host supports USB 3.0 SuperSpeed
[ 1.353514] usb usb1: New USB device found, idVendor=1d6b, idProduct=0002, bcdDevice= 6.14
[ 1.353517] usb usb1: New USB device strings: Mfr=3, Product=2, SerialNumber=1
[ 1.353520] usb usb1: Product: xHCI Host Controller
[ 1.353522] usb usb1: Manufacturer: Linux 6.14.0-37-generic xhci-hcd
[ 1.353524] usb usb1: SerialNumber: 0000:00:14.0
[ 1.353740] hub 1-0:1.0: USB hub found
[ 1.357134] usb usb2: New USB device found, idVendor=1d6b, idProduct=0003, bcdDevice= 6.14
[ 1.357138] usb usb2: New USB device strings: Mfr=3, Product=2, SerialNumber=1
[ 1.357141] usb usb2: Product: xHCI Host Controller
[ 1.357143] usb usb2: Manufacturer: Linux 6.14.0-37-generic xhci-hcd
[ 1.357145] usb usb2: SerialNumber: 0000:00:14.0
[ 1.357288] hub 2-0:1.0: USB hub found
[ 1.595635] usb 1-4: new full-speed USB device number 2 using xhci_hcd
[ 1.731494] usb 1-4: New USB device found, idVendor=0cf3, idProduct=e300, bcdDevice= 0.01
[ 1.731502] usb 1-4: New USB device strings: Mfr=0, Product=0, SerialNumber=0
[ 1.877816] usb 1-7: new full-speed USB device number 3 using xhci_hcd
[ 2.002594] usb 1-7: New USB device found, idVendor=138a, idProduct=0091, bcdDevice= 1.64
[ 2.002605] usb 1-7: New USB device strings: Mfr=0, Product=0, SerialNumber=1
[ 2.002609] usb 1-7: SerialNumber: 5514a8002548
[ 2.118603] usb 1-9: new full-speed USB device number 4 using xhci_hcd
[ 2.244541] usb 1-9: New USB device found, idVendor=04f3, idProduct=24a1, bcdDevice=11.11
[ 2.244548] usb 1-9: New USB device strings: Mfr=4, Product=14, SerialNumber=0
[ 2.244550] usb 1-9: Product: Touchscreen
[ 2.244552] usb 1-9: Manufacturer: ELAN
[ 2.357917] usb 1-12: new high-speed USB device number 5 using xhci_hcd
[ 2.517888] usb 1-12: New USB device found, idVendor=0c45, idProduct=6713, bcdDevice=56.05
[ 2.517907] usb 1-12: New USB device strings: Mfr=2, Product=1, SerialNumber=0
[ 2.517913] usb 1-12: Product: Integrated_Webcam_HD
[ 2.517918] usb 1-12: Manufacturer: CN045G28LOG00766B37AA01
[ 2.547589] input: ELAN Touchscreen as /devices/pci0000:00/0000:00:14.0/usb1/1-9/1-9:1.0/0003:04F3:24A1.0002/input/input13
[ 2.547841] input: ELAN Touchscreen UNKNOWN as /devices/pci0000:00/0000:00:14.0/usb1/1-9/1-9:1.0/0003:04F3:24A1.0002/input/input14
[ 2.547981] input: ELAN Touchscreen UNKNOWN as /devices/pci0000:00/0000:00:14.0/usb1/1-9/1-9:1.0/0003:04F3:24A1.0002/input/input15
[ 2.548295] hid-multitouch 0003:04F3:24A1.0002: input,hiddev0,hidraw1: USB HID v1.10 Device [ELAN Touchscreen] on usb-0000:00:14.0-9/input0
[ 2.548337] usbcore: registered new interface driver usbhid
[ 2.548339] usbhid: USB HID core driver
[ 4.705624] usb 1-12: Found UVC 1.00 device Integrated_Webcam_HD (0c45:6713)
[ 4.761604] usbcore: registered new interface driver uvcvideo
[ 4.781041] usbcore: registered new interface driver btusb
[ 4.782654] Bluetooth: hci0: using rampatch file: qca/rampatch_usb_00000302.bin
[ 5.138276] Bluetooth: hci0: using NVM file: qca/nvm_usb_00000302.bin
Plug in USB thumb drive stick. The device, interesting to note, is on Bus 002 Device 002.
$ lsusb
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 002: ID 0cf3:e300 Qualcomm Atheros Communications QCA61x4 Bluetooth 4.0
Bus 001 Device 003: ID 138a:0091 Validity Sensors, Inc. VFS7552 Touch Fingerprint Sensor
Bus 001 Device 004: ID 04f3:24a1 Elan Microelectronics Corp. Touchscreen
Bus 001 Device 005: ID 0c45:6713 Microdia Integrated_Webcam_HD
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 002 Device 002: ID 13fe:5500 Phison Electronics Corp. Flash drive
Unplug USB thumb drive stick.
$ lsusb
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 002: ID 0cf3:e300 Qualcomm Atheros Communications QCA61x4 Bluetooth 4.0
Bus 001 Device 003: ID 138a:0091 Validity Sensors, Inc. VFS7552 Touch Fingerprint Sensor
Bus 001 Device 004: ID 04f3:24a1 Elan Microelectronics Corp. Touchscreen
Bus 001 Device 005: ID 0c45:6713 Microdia Integrated_Webcam_HD
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Plug in USB thumb drive stick. A second time. The device is on Bus 002 Device 003.
$ lsusb
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 002: ID 0cf3:e300 Qualcomm Atheros Communications QCA61x4 Bluetooth 4.0
Bus 001 Device 003: ID 138a:0091 Validity Sensors, Inc. VFS7552 Touch Fingerprint Sensor
Bus 001 Device 004: ID 04f3:24a1 Elan Microelectronics Corp. Touchscreen
Bus 001 Device 005: ID 0c45:6713 Microdia Integrated_Webcam_HD
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 002 Device 003: ID 13fe:5500 Phison Electronics Corp. Flash drive
Unplug USB thumb drive stick.
$ sudo dmesg | grep -1 usb
[sudo] password for york-earwaker:
[ 0.475567] ACPI: bus type USB registered
[ 0.475567] usbcore: registered new interface driver usbfs
[ 0.475567] usbcore: registered new interface driver hub
[ 0.475567] usbcore: registered new device driver usb
[ 0.475567] pps_core: LinuxPPS API ver. 1 registered
--
[ 1.353465] xhci_hcd 0000:00:14.0: Host supports USB 3.0 SuperSpeed
[ 1.353514] usb usb1: New USB device found, idVendor=1d6b, idProduct=0002, bcdDevice= 6.14
[ 1.353517] usb usb1: New USB device strings: Mfr=3, Product=2, SerialNumber=1
[ 1.353520] usb usb1: Product: xHCI Host Controller
[ 1.353522] usb usb1: Manufacturer: Linux 6.14.0-37-generic xhci-hcd
[ 1.353524] usb usb1: SerialNumber: 0000:00:14.0
[ 1.353740] hub 1-0:1.0: USB hub found
[ 1.353778] hub 1-0:1.0: 16 ports detected
[ 1.357134] usb usb2: New USB device found, idVendor=1d6b, idProduct=0003, bcdDevice= 6.14
[ 1.357138] usb usb2: New USB device strings: Mfr=3, Product=2, SerialNumber=1
[ 1.357141] usb usb2: Product: xHCI Host Controller
[ 1.357143] usb usb2: Manufacturer: Linux 6.14.0-37-generic xhci-hcd
[ 1.357145] usb usb2: SerialNumber: 0000:00:14.0
[ 1.357288] hub 2-0:1.0: USB hub found
--
[ 1.572730] clocksource: Switched to clocksource tsc
[ 1.595635] usb 1-4: new full-speed USB device number 2 using xhci_hcd
[ 1.677077] wmi_bus wmi_bus-PNP0C14:03: [Firmware Bug]: WQBC data block query control method not found
--
[ 1.726759] scsi host0: ahci
[ 1.731494] usb 1-4: New USB device found, idVendor=0cf3, idProduct=e300, bcdDevice= 0.01
[ 1.731502] usb 1-4: New USB device strings: Mfr=0, Product=0, SerialNumber=0
[ 1.733088] scsi host1: ahci
--
[ 1.754602] platform i2c_designware.1: Adding to iommu group 19
[ 1.877816] usb 1-7: new full-speed USB device number 3 using xhci_hcd
[ 2.002594] usb 1-7: New USB device found, idVendor=138a, idProduct=0091, bcdDevice= 1.64
[ 2.002605] usb 1-7: New USB device strings: Mfr=0, Product=0, SerialNumber=1
[ 2.002609] usb 1-7: SerialNumber: 5514a8002548
[ 2.040407] ata2: SATA link down (SStatus 4 SControl 300)
[ 2.118603] usb 1-9: new full-speed USB device number 4 using xhci_hcd
[ 2.164768] nvme nvme0: pci function 0000:04:00.0
--
[ 2.201953] nvme nvme0: allocated 64 MiB host memory buffer (1 segment).
[ 2.244541] usb 1-9: New USB device found, idVendor=04f3, idProduct=24a1, bcdDevice=11.11
[ 2.244548] usb 1-9: New USB device strings: Mfr=4, Product=14, SerialNumber=0
[ 2.244550] usb 1-9: Product: Touchscreen
[ 2.244552] usb 1-9: Manufacturer: ELAN
[ 2.244860] nvme nvme0: 8/0/0 default/read/poll queues
--
[ 2.302468] hid-multitouch 0018:06CB:7A13.0001: input,hidraw0: I2C HID v1.00 Mouse [DLL07BE:01 06CB:7A13] on i2c-DLL07BE:01
[ 2.357917] usb 1-12: new high-speed USB device number 5 using xhci_hcd
[ 2.517888] usb 1-12: New USB device found, idVendor=0c45, idProduct=6713, bcdDevice=56.05
[ 2.517907] usb 1-12: New USB device strings: Mfr=2, Product=1, SerialNumber=0
[ 2.517913] usb 1-12: Product: Integrated_Webcam_HD
[ 2.517918] usb 1-12: Manufacturer: CN045G28LOG00766B37AA01
[ 2.547589] input: ELAN Touchscreen as /devices/pci0000:00/0000:00:14.0/usb1/1-9/1-9:1.0/0003:04F3:24A1.0002/input/input13
[ 2.547841] input: ELAN Touchscreen UNKNOWN as /devices/pci0000:00/0000:00:14.0/usb1/1-9/1-9:1.0/0003:04F3:24A1.0002/input/input14
[ 2.547981] input: ELAN Touchscreen UNKNOWN as /devices/pci0000:00/0000:00:14.0/usb1/1-9/1-9:1.0/0003:04F3:24A1.0002/input/input15
[ 2.548295] hid-multitouch 0003:04F3:24A1.0002: input,hiddev0,hidraw1: USB HID v1.10 Device [ELAN Touchscreen] on usb-0000:00:14.0-9/input0
[ 2.548337] usbcore: registered new interface driver usbhid
[ 2.548339] usbhid: USB HID core driver
[ 2.838103] EXT4-fs (nvme0n1p2): mounted filesystem 4b3393f8-940b-434d-bfda-7e738a90d1a8 ro with ordered data mode. Quota mode: none.
--
[ 4.697762] AES CTR mode by8 optimization enabled
[ 4.705624] usb 1-12: Found UVC 1.00 device Integrated_Webcam_HD (0c45:6713)
[ 4.715843] ACPI: battery: new hook: Dell Primary Battery Extension
--
[ 4.747895] audit: type=1400 audit(1766661620.883:10): apparmor="STATUS" operation="profile_load" profile="unconfined" name="brave" pid=696 comm="apparmor_parser"
[ 4.761604] usbcore: registered new interface driver uvcvideo
[ 4.764611] [drm] Initialized i915 1.6.0 for 0000:00:02.0 on minor 1
[ 4.781041] usbcore: registered new interface driver btusb
[ 4.782654] Bluetooth: hci0: using rampatch file: qca/rampatch_usb_00000302.bin
[ 4.782660] Bluetooth: hci0: QCA: patch rome 0x302 build 0x3e8, firmware rome 0x302 build 0x111
--
[ 5.113585] ath10k_pci 0000:02:00.0: htt-ver 3.87 wmi-op 4 htt-op 3 cal otp max-sta 32 raw 0 hwcrypto 1
[ 5.138276] Bluetooth: hci0: using NVM file: qca/nvm_usb_00000302.bin
[ 5.161349] Bluetooth: hci0: HCI Enhanced Setup Synchronous Connection command is advertised, but not supported.
--
[ 2901.325004] audit: type=1400 audit(1766664517.319:430): apparmor="DENIED" operation="open" class="file" profile="snap.brave.brave" name="/proc/3992/smaps_rollup" pid=3992 comm="MemoryInfra" requested_mask="r" denied_mask="r" fsuid=1000 ouid=1000
[ 2936.159214] usb 2-2: new SuperSpeed USB device number 2 using xhci_hcd
[ 2936.171910] usb 2-2: New USB device found, idVendor=13fe, idProduct=5500, bcdDevice= 1.10
[ 2936.171925] usb 2-2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 2936.171932] usb 2-2: Product: USB DISK 3.0
[ 2936.171937] usb 2-2: Manufacturer:
[ 2936.171942] usb 2-2: SerialNumber: 070B78FB9DFE7C22
[ 2936.225843] usb-storage 2-2:1.0: USB Mass Storage device detected
[ 2936.226055] scsi host2: usb-storage 2-2:1.0
[ 2936.226162] usbcore: registered new interface driver usb-storage
[ 2936.228825] usbcore: registered new interface driver uas
[ 2937.265276] scsi 2:0:0:0: Direct-Access USB DISK 3.0 PMAP PQ: 0 ANSI: 6
--
[ 3063.878285] audit: type=1400 audit(1766664679.875:434): apparmor="DENIED" operation="open" class="file" profile="snap.brave.brave" name="/proc/pressure/memory" pid=3992 comm="ThreadPoolForeg" requested_mask="r" denied_mask="r" fsuid=1000 ouid=0
[ 3190.179739] usb 2-2: USB disconnect, device number 2
[ 3201.321821] audit: type=1400 audit(1766664817.319:435): apparmor="DENIED" operation="open" class="file" profile="snap.brave.brave" name="/proc/3992/smaps_rollup" pid=3992 comm="MemoryInfra" requested_mask="r" denied_mask="r" fsuid=1000 ouid=1000
[ 3256.940868] usb 2-2: new SuperSpeed USB device number 3 using xhci_hcd
[ 3256.953066] usb 2-2: New USB device found, idVendor=13fe, idProduct=5500, bcdDevice= 1.10
[ 3256.953080] usb 2-2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 3256.953087] usb 2-2: Product: USB DISK 3.0
[ 3256.953092] usb 2-2: Manufacturer:
[ 3256.953097] usb 2-2: SerialNumber: 070B78FB9DFE7C22
[ 3256.956263] usb-storage 2-2:1.0: USB Mass Storage device detected
[ 3256.956840] scsi host2: usb-storage 2-2:1.0
[ 3257.966991] scsi 2:0:0:0: Direct-Access USB DISK 3.0 PMAP PQ: 0 ANSI: 6
--
[ 3258.303810] FAT-fs (sda1): Volume was not properly unmounted. Some data may be corrupt. Please run fsck.
[ 3594.101133] usb 2-2: USB disconnect, device number 3
Possibly the issue not unmounting the device before disconnecting it? Or is mouint/unmount just correlation and not causation.
My understanding of what is actually going on in Linux is somewhat limited. And I don't understand the causal chain events and/or the design rationale for constantly incrementing the device number.
Suppose one rationale for keeping count using the constant increment of the device number of USB devices plugged into host might be to track USB connections over time.
The device number is not a count of the number of devices actually plugged in at a given moment in time to the host.
The device number appears to be a count of the number of devices plugged in, to a given Bus, over a period of time to the host . The period of time since the last power down and power up cycle.
However you mentioned in another post that the device number is reset when it reaches a given maximum, modulo 127.
Possibly it might not have been considered that the maximum would ever be exceeded? That is that it was not conceived that 127 USB devices would be plugged and unplugged in any one host power up power down cycle. Or the register in which the device number (count) is held is only capable of holding 127 bits?
Still not clear on what the architectural design rationale is for incrementing the USB device number. Perhaps there are several uses, use cases, to which this device number count is put. Wonder if there is a design document somewhere in Linux kernel world which addressed this specific design rationale?
Every separate USB Bus appears to have its own distinct 'register' of modulo 127, 128 bits, which is used to keep track of device number (count). That is number of USB devices plugged into the host on a respective USB Bus over time.
Suppose it might be a requirement of the USB specifications from USB Implementer Forum USB-IF. Was looking at some of those specs regarding another post on this RPi Forum.
Thanks for your time on this post.
Yours,
York
Statistics: Posted by York Earwaker — Thu Dec 25, 2025 12:42 pm