Accessing a USB device

[Charles Hallenbeck]

I am trying for the first time to access a USB device and having a 
problem doing so. The device is my new UPS from American Power 
Conversion, which I plan to monitor with a program called apcupsd. The 
manual describes how to configure my system for USB and how to test the 
USB interface before running the program, and that is where I am stuck.

It appears to me to be an interrupt problem. Here is why I think so. For 
the past month or two I have noticed a peculiarity that happens within 
about a minute after booting up the computer. Normally I start logging 
in various users on difference consoles, and while I am doing that, I 
get a spontaneous message saying that IRQ 5 is being disabled. The 
message says something cute like, "Nobody cares!" and then disables IRQ 
5. Examining the IRQ assignments, I see that the only device assigned to 
that IRQ shown in /proc/interrupts is the uhci-hcd driver. That has not 
been a problem until now, since until now I have not attempted to access 
a USB device, which requires the uhci-hcd driver.

When I plug the cable from my UPS into a USB slot, the device is 
correctly identified by manufacturer, serial number, etc., but then it 
says that it fails to register with usbcore. And the test program 
confirms that the device cannot be accessed.

My kernel is 2.6.11.6, and all the relevant drivers are compiled into 
the kernel. It looks to me like the uhci-hcd driver has been assigned to 
IRQ 5 but is not responding to that interrupt when it occurs. If someone 
has seen this kind of thing before, or has any suggestion how to proceed 
with troubleshooting this one, I would sure appreciate hearing about it. 
The software I plan to run to monitor the UPS is not involved here as 
yet, since I have to resolve the USB interface to the UPS before there 
is a hope in hell of that software working. If it would be of value to 
share any of the error messages or other data, I would be happy to do 
so.

Any ideas? I have run out.

Chuck


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