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I am using a library (librealsense) that only outputs the bus and port number as such (9.1). It uses libusb internally. The issue is from this identifier in libusb I want to know what physical device it belongs to in /dev/video0. For instance, 9.1 -> /dev/video0 and 7.2 -> /dev/video2 when two cameras are plugged in in ports 9.1 and 7.2.

Is this possible? How do I acquire what devices paths belong to a bus and port? Any partial answer would be helpful.

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    Don't know your OS, but if the devices are created via udev, you could use udevadm info -n video0 -q all to see the created symlinks; e.g. S: v4l/by-path/pci-0000:00:13.2-usb-0:4.1:1.0-video-index0 shows the link in /dev/v4l/by-path. Or, if you know the ID of your cameras, /dev/v4l/by-idcould help. And configuring udev might give fixed devices for different cameras. – ridgy Feb 14 '17 at 10:43
  • You can do it the other way round (find which usb device belongs to which video* device) by examining /sys/class/video4linux/, which contains symlinks with the complete bus path (usb or otherwise). – dirkt Feb 14 '17 at 11:14
  • @ridgy Thanks that's what I was looking for, I can grep for existence of that path! Feel free to copy that as an answer, if you want. – nico Feb 14 '17 at 15:23
  • @dirkt I appreciate your answer, I tried that but I'm not quite sure which directory the video information is location within the /sys/class/video4linux folder. – nico Feb 14 '17 at 15:23
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    Just do ls -l /sys/class/video4linux/, you should see all video devices as symlinks. udevadm also just looks at the /sys file system, but extracts more information from it (most of which you don't need for your question). – dirkt Feb 14 '17 at 16:52
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Answering so I can close this question full credit to @ridgy and @dirkt for their help. With the command:

udevadm info -n video0 -q path

Or similarly with ls -l /sys/class/video4linux/, a path of the form /devices/pci0000:00/0000:00:10.0/usb7/7-2/7-2:1.0/video4linux/video0 can be found. That in combination with the listing of the video devices using either ls /dev/video* or v4l2-ctl --list-devices allows a map between the usb port and video device to be created.

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you can also use below command to get more information

udevadm info -a -p $(udevadm info -q path -n /dev/video0)

udevadm info -a -p $(udevadm info -q path -n /dev/video1)

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