I'm following this guide on passing through an entire USB controller to a VM.

At one point he says to plug in a flash drive to every USB port on the computer to see which ports correspond to which bus.

Weird thing is that I plugged 2 different devices into the same port, and lsusb always reported BUS 3 for one device, and BUS 4 for the other.

Why is that?

  • 1
    could be one device is USB2 the other is USB3, which will "route" to a different controller or port or whatever
    – A.B
    Jul 1 '18 at 19:12
  • That's what I'm suspecting now as well. Darn Jul 1 '18 at 19:14
  • BTW, lsusb -t really helps to debug which port belongs to which root, including the distinction between USB2 and USB3.
    – dirkt
    Jul 2 '18 at 9:58

After a bit more testing, I found that any USB 3 device plugged into a USB 3 slot was mapped to BUS 4. Any USB 2 device plugged into any USB 3 slot was mapped to BUS 3.

However any USB 3 device plugged into a USB 2 slot was mapped to BUS 3.

Seems that the LCD determines the BUS.

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