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    SubjectRe: [linux-usb-devel] [PATCH] USB: consolidate error values from EHCI, UHCI and OHCI _suspend()
    On Tue, 19 Sep 2006, Jiri Kosina wrote:

    > On Mon, 18 Sep 2006, David Brownell wrote:
    > > > EHCI, UHCI and OHCI USB host drivers are not consistent when returining
    > > > error values from their _suspend() functions, in case that the device is
    > > > not in suspended state. This could confuse users, so let all three of them
    > > > return -EBUSY.
    > > Shouldn't you also update uhci_suspend()? Currently it just ignores
    > > hcd->state ...
    > You are right that the patch is possibly not fully correct. I was trying
    > to fix the situation I was getting into with the bug in usb_resume_both()
    > (see my "[PATCH] 2.6.18-rc6-mm2 - usb_resume_both() - fix suspend/resume"
    > mail from yesterday), but now it is obvious that the EINVAL from UHCI is
    > of a "different kind" than EBUSY from OHCI and UHCI (though they are
    > triggered in the same situations -- when the previous resume was not done
    > correctly).

    Sort of. The real trigger is that the PM core tries to suspend the
    upper-level PCI device but the lower-level root-hub device has not been
    suspended. You saw this occurring because during the previous resume, the
    root-hub device's power.power_state.event was not updated, causing the PM
    core to think the root hub was still suspended when in fact it wasn't.

    > As far as I can see, the UHCI driver is, strangely enough, not using
    > hcd->state at all.
    > (by the way, EHCI and OHCI seem to have broken (read: missing) locking
    > when accessing the hcd->state. Should I fix it by per-hcd spinlock, or
    > does the patch already exist somewhere?)

    Believe it or not, these two paragraphs are closely connected. The reason
    uhci-hcd doesn't use hcd->state at all is because there is no locking to
    protect it!

    My feeling has long been that hcd->state deserves to disappear. It tries
    to serve too many functions. Please don't add any code in a futile
    attempt to preserve it.

    Alan Stern

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