Difference between revisions of "USB Device Diagnostics in Linux"

Revision as of 20:17, 28 February 2019

To detect your USB device, in a terminal, you can try:

lsusb
lsusb -v

The second, verbose, offering more detail.

Device are mainly identified using a pair of hexadecimal numbers, like 04b3:3108

The 4 first hexadecimal digits are the Vendor ID (04b3 = IBM).

The 4 last hexadecimal digits are the Device ID (3108 = ThinkPad 800dpi Optical Travel Mouse).

When your device is listed as "unknown" you can update your local usb-id definition by running update-usbids as root.

Try this:

lsusb -v | grep -E '\<(Bus|iProduct|bDeviceClass|bDeviceProtocol)' 2>/dev/null

Another way is to dump the information from the running kernel

sudo cat /sys/kernel/debug/usb/devices

Parse it a little

sudo cat /sys/kernel/debug/usb/devices | grep -E "^([TSPD]:.*|)$"

USB Input Devices

Input devices include keyboards, mice, remotes, etc.

They do not include flash drives.

xev - Tool that can provide keycodes from input devices. Useful after you have determined your usb input device works and if it is a hid device like a keyboard or mouse. see Multimedia Keys for details on getting the codes from those extra keys in a keyboard.

summary

Another tool that provides extensive details for USB diagnostics:

sudo lsinput

You may have to install it first, it is part of input-utils

sudo apt install input-utils

A tool to show the device being recognized when inserted is

udevadm monitor --udev

The udevadm command cannot be run by itself. You must include a parameter to tell it what to do.

input-utils package

input-utils: utilities for the input layer of the Linux kernel: This is a collection of utilities which are useful when working with the input layer of the Linux kernel (version 2.6 and later). Included are utilities to list the input devices known to the kernel, show the input events that are received by a device, and query or modify keyboard maps. Specifically the tools deal with /dev/input/event* input devices.

• lsinput - dumps out all the input devices and the associated details
• input-kbd - dump out the keyboard mapping of a particular event device, must specify the device number such as 'sudo input-kbd 3'
• input-events - observe input events for watching a specific input device, must specify the device number such as 'sudo input-events 3'

udevadm

udevadm can be used to monitor USB connections

udevadm -h
Usage: udevadm [--help] [--version] [--debug] COMMAND [COMMAND OPTIONS]
  info         query sysfs or the udev database
  trigger      request events from the kernel
  settle       wait for the event queue to finish
  control      control the udev daemon
  monitor      listen to kernel and udev events
  hwdb         maintain the hardware database index
  test         test an event run
  test-builtin test a built-in command

To monitor USB connections here are some command usage examples:

udevadm monitor --subsystem-match=usb --property
udevadm monitor --subsystem-match=usb --property --udev

discover package

use the command discover

discover

a working example

I have connected a tiny USB receiver for an unknown pointing device. The manufacturer is unknown. I'm not sure if it is the correct dongle and if the device works. Here is where I start:

udevadm monitor --udev

Now that it is running, I will insert the USB receiver.

A lot of information showed up. Too many lines to share here. Whats important is this one:

UDEV  [42556.827151] add      /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.7/2-1.7:1.0/0003:26E3:106C.0015 (hid)

I can find the device identification which is: 0003:26E3:106C.0015 and that it is a human interface device (hid) which includes the category of mouse and keyboard

Lets look at 0003:26E3:106C.0015, right now we care about the second and third part of the HEX values each part separated by a :

• 26E3 = the vendor or manufacturer, as a hex value 0x26e3
• 106C = the product name, as a hex value 0x106c

Now we have a way to match up the device, and we know the device was recognized by the system.

I use control-c to get out of udevadm monitor and now run 'lsusb' and I get:

Bus 002 Device 008: ID 26e3:106c  
Bus 002 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
[...]

Now I can see that the device 008 is my device because I match the 26e3:106c up. However, lsusb isn't telling me a name. Must not be in its database.

Lets try the command 'sudo lsinput' which spits out a lot of devices. Look through the output and find the group with the matching hex value. Like this:

/dev/input/event7
   bustype : BUS_USB
   vendor  : 0x26e3
   product : 0x106c
   version : 257
   name    : "EXCEL EXCELDIGI Wireless Device"
   phys    : "usb-0000:00:1d.0-1.7/input1"
   uniq    : ""
   bits ev : EV_SYN EV_KEY EV_REL EV_MSC

Ok, now I know

• 26E3 (0x26e3) = EXCEL EXCELDIGI
• 106C (0x106c) = Wireless Device

I can also tell it is an input device. Next lets see if it provides input to the computer, or more accurately, if the computer is seeing input from the device when I turn the device on and press buttons or move it.

We're going to use the command 'sudo input-events' yet we need to know the device number so we can add it to the end of the command. Above we see from the output of lsinput "event7" so the device number is 7 and we will issue the command like this: 'sudo input-events 7'

Nothing happens until the device is manipulated, such as pressing a button or moving it. Now information begins scrolling up the screen indicating the kernel is getting input from the device. here is a sample:

19:48:45.979478: EV_SYN code=0 value=0
19:48:45.987504: EV_REL REL_X 13
19:48:45.987504: EV_REL REL_Y -11

Those are input coordinates from pointer events, so now we can tell we have a pointing device.

This concludes the example using the mystery device.