Subject: uhub w/ external power: device problem, disabling port
To: None <>
From: Hubert Feyrer <>
List: tech-kern
Date: 10/29/2006 14:49:39
I've came across a driver problem that I hope someone can help me with:

I have a very old laptop on which I have to boot a kernel from floppy, and 
then have root on an external USB disk (the laptop's BIOS won't recognize 
any modern disk size, and there is no update available). The USB disk is 
behind a cardbus->4*usb card and has two USB connectors for power reasons. 
Besides the disk, I want to connect two usb->ethernet dongles, and to 
power all that, the cardbus->usb card has external power.

Now when I try to operate just the card with external power and add an
usb->ethernet dongle (or two), uhub(4) thinks there's a device problem and 
disables the port:

 	uhub0: device problem, disabling port 1

I've looked in the uhub.c code and even added some retries, but they 
always bring errors. As soon as I unplug the external power (which isn't 
needed for ethernet), the dongle is recognized properly.

FWIW, the power supply is according to the specs of the card (5V, 2A), and 
I can reproduce the problems on a cardbus->2*usb as well as on a 
cardbus->4*usb card.

Is there any known problem with external power supplies on cardbus->usb 
adapters and our uhub(4)?


  - Hubert

P.S.: I've tried ~every other combination of the devices, including an 
externally powered usb hub, but neither USB ethernet nor the disk seem to 
work well behind the hub. From what I've heared at least USB ethernets 
have problems behind hubs on other operating systems (Windows) as well, so 
that's why I'd like to get things on this cardbus->4*usb card going.