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From: Alan Stern <>
To: Larry Finger <>
Cc: Greg Kroah-Hartman <>, <>,
	LKML <>
Subject: Re: [PATCH] usbcore: Limit number of 'unable to enumerate USB device' messages
Date: Fri, 24 Oct 2008 09:57:37 -0400 (EDT)	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Thu, 23 Oct 2008, Larry Finger wrote:

> In my system, a number of messages that state "unable to enumerate USB device"
> are logged. These are intermittent and likely due to some race condition
> at bootup.
> Some of these happen when the EHCI driver is loaded after UHCI or OHCI, which
> causes the device to be switched away from the other controller that's trying
> to enumerate it, at least momentarily. This type of message is logged at most
> once for each hub and occurs in about 70% of my reboots.

This is normal; it is caused by userspace loading the drivers in the
wrong order.  ehci-hcd is supposed to be loaded before uhci-hcd or
ohci-hcd, not after.  There's no point trying to change the kernel to
avoid it.

> A more insidious form of the message occurs hundreds of times in about 10% of
> reboots. They continue until the system is rebooted. This patch limits the
> number of these messages to 20. Once the actual cause of this message is
> located, this patch can be reverted.

I would prefer to attack this problem directly rather than wallpaper 
over it.  Can you provide more information?  For example, a dmesg log 
with CONFIG_USB_DEBUG and CONFIG_PRINTK_TIME enabled would help.  It 
might also help to know what the devices which can't be enumerated 
actually are.

Alan Stern

      parent reply	other threads:[~2008-10-24 13:57 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-10-23 23:35 [PATCH] usbcore: Limit number of 'unable to enumerate USB device' messages Larry Finger
2008-10-23 23:36 ` Greg KH
2008-10-24 16:25   ` Larry Finger
2008-10-24 17:00     ` Greg KH
2008-10-25  3:16       ` Larry Finger
2008-10-25 14:59         ` Alan Stern
2008-10-27 16:37           ` Larry Finger
2008-10-24 13:57 ` Alan Stern [this message]

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