Re: Understanding 'lsusb -t'

[Greg KH <gregkh@linuxfoundation.org>]

On Fri, Aug 30, 2024 at 10:14:20PM +1000, Eyal Lebedinsky wrote:
> I assume that the generated list is a tree, so each leaf (Device/If) is on only one point.
> 
> I note this output:
> 
> $ lsusb -tv
> /:  Bus 001.Port 001: Dev 001, Class=root_hub, Driver=xhci_hcd/16p, 480M
>     ID 1d6b:0002 Linux Foundation 2.0 root hub
> [trimmed]
>     |__ Port 004: Dev 004, If 0, Class=Hub, Driver=hub/4p, 480M
> [trimmed]
>     |__ Port 005: Dev 006, If 0, Class=Hub, Driver=hub/4p, 480M
> [trimmed]
>     |__ Port 006: Dev 019, If 0, Class=Hub, Driver=hub/4p, 480M
>         ID 2109:2817 VIA Labs, Inc.
> /:  Bus 002.Port 001: Dev 001, Class=root_hub, Driver=xhci_hcd/10p, 10000M
> [trimmed]
>     |__ Port 006: Dev 006, If 0, Class=Hub, Driver=hub/4p, 5000M
>         ID 2109:0817 VIA Labs, Inc.
> 
> I removed some content that is not relevant to my question.
> 
> Note the Bus 001.Port 006 and Bus 002.Port 006 entries.
> 
> I verified that both are for the same (one) device. They do not show when I disconnect it.
> The device is an external 4-port USB3.0 hub. It is listed once as 480M and once as 5000M.
> Nothing is plugged into any of the four ports.
> 
> Is this correct? Why does this device show twice in the list?

That's odd, as the same device shouldn't be on multiple busses.  Busses
are a "root port" on the system (i.e. a new PCI controller device), so
are you sure you just don't have multiple devices with the same
device/vendor id?

What is the diff between running the command before and after removing a
single device?

thanks,

greg k-h