Skip to main content
Start a Conversation

Unsolved

This post is more than 5 years old

relevant

161 Posts

1401

June 23rd, 2016 13:00

lsusb on XPS 13 (9343): two USB 2.0 buses and one USB 3.0 bus

Hi, I have some questions regarding the output of lsusb on my XPS 13:

$ lsusb 

Bus 003 Device 002: ID 8087:8001 Intel Corp.
Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 002: ID 0c45:670c Microdia
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
$

I have two normal-sized USB ports, and both of those are 3.0. I guess the display port is 2.0? But why have two 2.0 buses for that display port? I find it strange that two USB 3.0 physical ports map to one bus. Is that normal? If I use two USB 3.0 devices, since only one bus controls both of them does that mean that they both cannot operate at full speed at the same time?

I know nothing about this stuff so my questions are just for the sake of quenching curiosity. I would love to learn more.

cloph

74 Posts

July 13th, 2016 06:00

There are not two usb 2.0 buses for display port, one of them is the usb 2.0 compatibility layer for the 3.0 one.

When you connect a usb 2.0 device to one of the ports, it will be associated with the 2.0 hub, if it is a usb 3  device, it will be associated with the 3.0 one. Compare the following "lsusb.py -c" outputs:

  • first usb 2.0 (android phone) connected to the right usb port (where cardreader is), and usb 3.0 storage stick connected to the left usb port (where power-connector and headphone jack is):

    usb1    1d6b:0002 09  2.00  480MBit/s 0mA 1IF  (ehci_hcd 0000:00:1d.0) hub

     1-1    8087:8001 09  2.00  480MBit/s 0mA 1IF  (Intel Corp.) hub

    usb2    1d6b:0002 09  2.00  480MBit/s 0mA 1IF  (Linux 4.4.13-desktop-1.mga5 xhci-hcd xHCI Host Controller 0000:00:14.0) hub

     2-1    0bb4:0c02 00  2.00  480MBit/s 500mA 2IFs (MediaTek JY-G3 0123456789ABCDEF)

     2-3    0a5c:216f ff  2.00  > 12MBit/s 0mA 4IFs (Broadcom Corp BCM20702A0 C48E8FF4E832)

     2-5    0c45:670c ef  2.01  480MBit/s 500mA 2IFs (CN09GTFM7248754FB5YSA00 Integrated_Webcam_HD)

    usb3    1d6b:0003 09  3.00 5000MBit/s 0mA 1IF  (Linux 4.4.13-desktop-1.mga5 xhci-hcd xHCI Host Controller 0000:00:14.0) hub

     3-2    0781:5583 00  3.00 5000MBit/s 896mA 1IF  (SanDisk Ultra Fit 4C530001100531117360)

  • second with the devices connected to the opposite ports (android phone on the left, data-stick on the  right now):

    usb1    1d6b:0002 09  2.00  480MBit/s 0mA 1IF  (ehci_hcd 0000:00:1d.0) hub

     1-1    8087:8001 09  2.00  480MBit/s 0mA 1IF  (Intel Corp.) hub

    usb2    1d6b:0002 09  2.00  480MBit/s 0mA 1IF  (Linux 4.4.13-desktop-1.mga5 xhci-hcd xHCI Host Controller 0000:00:14.0) hub

     2-2    0bb4:0c02 00  2.00  480MBit/s 500mA 2IFs (MediaTek JY-G3 0123456789ABCDEF)

     2-3    0a5c:216f ff  2.00  > 12MBit/s 0mA 4IFs (Broadcom Corp BCM20702A0 C48E8FF4E832)

     2-5    0c45:670c ef  2.01  480MBit/s 500mA 2IFs (CN09GTFM7248754FB5YSA00 Integrated_Webcam_HD)

    usb3    1d6b:0003 09  3.00 5000MBit/s 0mA 1IF  (Linux 4.4.13-desktop-1.mga5 xhci-hcd xHCI Host Controller 0000:00:14.0) hub

     3-1    0781:5583 00  3.00 5000MBit/s 896mA 1IF  (SanDisk Ultra Fit 4C530001100531117360)

relevant

161 Posts

July 13th, 2016 14:00

Ah thank you for this information! I did not know about compatibilty layer but now I understand and that totally makes sense!

View More

View All

No Events found!

Top