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I ran lsusb on my Linux (Ubuntu) machine and here is my result:

Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 002: ID 8087:0020 Intel Corp. Integrated Rate Matching Hub
Bus 002 Device 002: ID 8087:0020 Intel Corp. Integrated Rate Matching Hub
Bus 001 Device 003: ID 413c:2005 Dell Computer Corp. RT7D50 Keyboard
Bus 001 Device 004: ID 413c:3016 Dell Computer Corp. Optical 5-Button Wheel Mouse
Bus 001 Device 005: ID 03f0:a007 Hewlett-Packard 

The last 3 entries are my USB keyboard, mouse, and headphones which makes sense since I have them physically plugged into the computer. I am confused on what the Linux Foundation 2.0 root hub and the Intel Corp. Integrated Rate Matching Hub is.

I also am wondering why some of the entries are listed twice and what the difference is between 'Bus' and 'Device'. Some of the entries are on bus 001 while others are on bus 002.

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2 Answers 2

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I had the same question - after some further research here is my attempt at a better answer: The output of lsusb gives you:

  1. Bus 001 The SB busses available on your machine. As far as I understand it (but please correct me if I am wrong), these are software-busses implemented in the Linux kernel without a physical equivalence. On my system for example, I have Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub, which is a 3.0 USB Bus. Yet my computer is an old model and does not have any USB 3.0 ports. Each bus serves as a root hub which can be linked to other hubs.
  2. Device 001 does not mean an actual physical device. Each entity gets its own device number, starting with 001 the root-hub itself. Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub is another internal hub at a lower level connected to the root-hub. To this hub other devices can be linked. The device numbers change every time you plug or unplug a physical device. In fact, if you unplug a device and replug it again, it gets assigned a new number. However Device 001 is always the root-hub of the corresponding bus.
  3. The number after the device e.g. ID 8087:0024 is the Manufacturer and Product ID You will find further explanation here: interpreting the output of lsusb
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That is probably usb units found on your motherboard.

And the bus tells you about where the unit is connected, more or less what usb controller is handling the device.

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