Can not connect bus-powered USB hubs?

James Wilkinson james at
Sun Nov 14 22:18:13 UTC 2004

Mark wrote:
> I switched from RH8 to FC1 some time ago. After that my USB-camera, which is
> connected to the PC with 2 single-port extension cables, didn't work anymore.
> Versions FC2 and FC3-test3 (that I am running now) have the same problem.
> Is there a solution to this problem?

So is that
USB port <-- extension cable --><-- extension cable --><-- USB camera -->
USB port <-- ext. cable --><-- ext. cable --><--camera cable--><-- camera -->

How complex are those cables? How likely is it that there are chips in

What happens if you take them out of the equation?

> Here's some output that may be of any help:
> Nov 12 23:32:55 amdrvk kernel: usb 2-2.2: can't connect bus-powered hub to this port

This message comes from drivers/usb/core/hub.c. Above it is the comment:
 /* consecutive bus-powered hubs aren't reliable; they can
  * violate the voltage drop budget.  if the new child has
  * a "powered" LED, users should notice we didn't enable it
  * (without reading syslog), even without per-port LEDs
  * on the parent.

The kernel may have become more fussy about proper cabling because the
alternative may well be lost data.

Hope this helps,


E-mail address: james |  ... File not found, I'll load something *I* think  |  is interesting.

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