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I posted this question first on StackOverflow. I got the hint to post it here with additional information. So here is the updated question.

Original question:

I tried to connect a usb webcam directly to my computer running linux. However the webcam doesn't get detectet. If I run lsusb there are only the "Linux Foundation root hub" things showing up but no device. Just to test I connected a passive usb hub with 4 ports to my computer and connected the webcam to the hub. Surprisingly the webcam shows up in lsusb.

Why does my computer only detect the webcam through a passive usb hub and not directly? Where is the difference and how to probably fix this issue?

Additional information:

It's a usb 2.0 hub with usb 2.0 webcam connected.

lsusb output when the webcam is connected through hub to computer:

Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 001 Device 003: ID 046d:082b Logitech, Inc.
Bus 001 Device 002: ID 05e3:0608 Genesys Logic, Inc. USB-2.0 4-Port HUB
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

lsusb output when the webcam is connected directly to computer:

Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

dmesg doesn't show something special when the webcam is connected directly to the computer.

Additional information #2:

If I connect the webcam directly to the computer it stays stable. But if I connect the webcam through the passive usb hub the computer shuts down (obviously because it draws to much power for a moment). But after the computer booted up again, it shows my webcam.

The "computer" is a C.H.I.P. from Next Thing Co. with only one usb port. I control it headless via ssh terminal.

Kind regards

  • @Xen2050 I corrected the question. You are right. :) – user765412 Aug 27 '17 at 14:43
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    Usually usb problems are related to bad wire/plug/power, or incompatible hub/devices, even the wrong moon phase, who knows... But especially if you're using the same wire and plugs then I'm not at all sure. dmesg might show more info when plugging in/umplugging, or syslog maybe even more info. – Xen2050 Aug 27 '17 at 14:51
  • @Xen2050 I disconnected and connected the webcam (directly to the computer). dmesg | tail didn't show a difference. Which syslogs could I provide? – user765412 Aug 27 '17 at 14:55
  • dmesg shows about 20 lines when I plug in a usb drive, it should show something if it's doing something, but that would be consistent with it not seeing it at all. Usually /var/log/syslog is a main one. – Xen2050 Aug 27 '17 at 15:05
  • What kind of USB host controller topology do you have in your "computer running Linux"? Does it have EHCI for USB2, UHCI or OHCI for other USB types? Did you try to look at device tree topology using more elaborate tool like USB tree viewer for Linux? superuser.com/q/1180854/620011 – Ale..chenski Aug 28 '17 at 2:17

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