On Wed, 12 Jul 2006, Robert Watkins wrote:

> > Looks like the keyboard got disconnected here.  Did you unplug it and try 
> > again?
> The dmesg output starts, I think soon before, me unplugging the
> keyboard, which I then reconnected via the cable. I only unpluged once. 

Okay.

> > There should have been more after this.  What happened to the "Cannot 
> > enable port 1" messages?
> There is a lot more of the same, please see the attached file
> dmesg_cable+kb.
> The "Cannot enable port 1" messages are not there. Could the patch you
> suggested have made the difference?

It should not have had this effect.  Just to be sure, you can try taking
the patch back out and see if the behavior changes.

> > Have you tried plugging the cable/keyboard into a different Linux 
> > computer?
> I've just tried the same keyboard and extension cable on a borrowed
> laptop, running Knoppix 5.0 which has a 2.6.17 linux. The keyboard
> worked happily with the extension cable. usbview showed a single ohci
> controller on the laptop and no ehci at all.

That definitely indicates there's nothing terribly wrong with the cable or 
the keyboard.

> I tried the same Knoppix CD with my new PC. The keyboard still did not
> work with an extension cable, even though it works with the BIOS, grub
> and the same Knoppix CD on a laptop.

And this indicates that there's something funny with the PC's USB 
hardware, or the connection between the PC and the cable, although it 
doesn't explain why things work okay with the BIOS.

The log messages don't point to any software problem.  What they say is
that the keyboard is repeatedly being connected, disconnected, connected,
disconnected,... over and over again.  (I mean electrically disconnected
from the USB bus, not physically unplugged from the port.)  For example,
maybe the extension cable doesn't make a firm contact with the pins in the
computer's USB port.

I can't tell how quickly these events occurred because your log doesn't 
contain any timestamps.  If you set CONFIG_PRINTK_TIME then the kernel 
will add timestamps to the log entries.

Either this electrical activity really is happening or else the OHCI 
controller only thinks it is.  The only way to tell the difference is by 
using a USB analyzer of some sort... but even that wouldn't tell us _why_ 
it is happening.

I don't have any good ideas on what to do.  One possibility is to try 
using a different extension cable.  Or instead of using an extension, get 
a USB hub.

Alan Stern



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