From: Alan Stern <stern@rowland.harvard.edu>
To: Eyal Lebedinsky <eyal@eyal.emu.id.au>
Cc: list linux-usb <linux-usb@vger.kernel.org>
Subject: Re: usb port enumeration changed?
Date: Mon, 26 Jul 2021 22:23:45 -0400 [thread overview]
Message-ID: <20210727022345.GA138425@rowland.harvard.edu> (raw)
In-Reply-To: <261c3985-28bc-b203-59fa-ecb650f2b42d@eyal.emu.id.au>
On Tue, Jul 27, 2021 at 11:15:11AM +1000, Eyal Lebedinsky wrote:
> 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.
Port numbers are stable. Bus numbers aren't. (They do tend to be stable
but there are no guarantees.)
> 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)
In fact it is device 25; see above. There is o device 11 in the lsusb
output.
> 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
Are you certain that device 3 really is one of the TEMPer devices and not
something else?
> This, naturally, confuses my script that collects the data from these sensors (I use temper-poll).
Are you certain you didn't change the wiring? I can't think of any other
explanation.
> Is this an intentional change?
Nope.
> If so then what is the way to stably disambiguate usb devices (there is no s/n available)?
Using port paths is a fairly good way to go. Unless the devices get
unplugged and then plugged back into different ports.
> If no change was expected then does this reflect a possible hwr problem here?
No, it represents a physical impossibility. Consider the following thought
experiment: You unplug the four-port hub that is device 6 on bus 1 (port
5). That will of course also disconnect anything that is plugged into that
hub, presumably including your two temperature sensors. But if one of them
is plugged into port 3 of the root hub instead, it won't be affected by
this operation. So what really happens?
Alan Stern
next prev parent reply other threads:[~2021-07-27 2:23 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-27 1:15 usb port enumeration changed? Eyal Lebedinsky
2021-07-27 2:23 ` Alan Stern [this message]
2021-07-27 6:43 ` usb port enumeration changed? [resolved] Eyal Lebedinsky
2021-07-27 13:39 ` Alan Stern
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