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    SubjectRe: USB devices fail unnecessarily on unpowered hubs
    On Thu, 1 Jun 2006, Andrew Morton wrote:

    > On Thu, 1 Jun 2006 10:58:43 -0400 (EDT)
    > Alan Stern <stern@rowland.harvard.edu> wrote:
    >
    > > As an alternative, we could allow an "over-budget window" of say 10%.
    >
    > That, plus we should provide a suitable i-know-what-im-doing user override,
    > with the appropriate warnings, as well as a printk which directs users to
    > this option when we decided to disable their device.

    The user override already exists, as do the appropriate warnings. Daniel
    Drake just added a printk explaining why the device was not configured,
    although it doesn't tell how to configure the device by hand. Perhaps a
    FAQ entry at www.linux-usb.org would be appropriate.

    > The power supply spec is a conservative minimum, whereas the device spec is
    > a worst-case maximum. One would expect a lot of devices will work OK when
    > run "out of spec".
    >
    > (Goes away and pats all his 240V plugpacks which are happily working off 110V).

    They probably will. The question is, how far out-of-spec should the
    kernel allow by default? 200% is likely to be too far (your plugpacks
    notwithstanding).

    Alan Stern

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