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    SubjectRe: [PATCH] usbcore: Limit number of 'unable to enumerate USB device' messages
    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

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