I can understand what is port but not getting the Bus and Dev.

Bus 04.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/2p, 10000M
    |__ Port 1: Dev 3, If 0, Class=Mass Storage, Driver=uas, 10000M
/:  Bus 03.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/2p, 480M
/:  Bus 02.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/10p, 10000M
/:  Bus 01.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/16p, 480M

1 Answer 1


Bus is a usb host controller, which is usually provided by the chipset or the motherboard. In your example there are four host controllers, two with USB 3.1 speeds (10000M), two with USB 2.0 speeds (480M). In practice these may use the same physical ports, as USB 2 devices on USB 3 ports will be shown connected to a USB 2 host controller / root hub.

Dev is a running number for a connected device. It will change every time the device is disconnected and reconnected, so it will have little practical use for the user.

For more, see e.g.:

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