linux-kernel - Re: Logs being spammed with "Unable to enumerate USB device"

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Message-ID: <48E2B868.9070407@lwfinger.net>
Date:	Tue, 30 Sep 2008 18:38:16 -0500
From:	Larry Finger <Larry.Finger@...inger.net>
To:	Larry Finger <Larry.Finger@...inger.net>
CC:	Robert Hancock <rwh461@...l.usask.ca>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Logs being spammed with "Unable to enumerate USB device"

Larry Finger wrote:
> Robert Hancock wrote:
>> Is this just occurring during bootup? I think this is normal if the EHCI
>> driver is loaded after UHCI or OHCI because it causes the device to be
>> switched away from the other controller that's trying to enumerate it,
>> at least momentarily.
> 
> It sometimes happens at bootup, but at other times I will get hundreds
> of them in a row in the logs. I have put in some debugging where the
> message is triggered, but have not seen any of the flood-type since.

I now have more information. The if statement that triggers the
message is as follows:

if (hub->hdev->parent ||
    !hcd->driver->port_handed_over ||
    !(hcd->driver->port_handed_over)(hcd, port1))

For all the messages that I have captured, the first condition
(hub->hdev->parent) is always true.

For the isolated message that occurs at bootup, the second condition
(!hcd->driver->port_handed_over) is true and the third is false.

When the message storm occurs, the second condition is false, i.e.
hcd->driver->port_handed_over is not zero, but
!(hcd->driver->port_handed_over)(hcd, port1) is true.

As before, I am willing to test any patches. As the message storm is
rare, it will be difficult to show that a patch fixes the problem.

Larry

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