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    SubjectRe: [PATCH 4/5] usb_serial: Kill port mutex
    On Thu, 8 Oct 2009, Oliver Neukum wrote:

    > Am Donnerstag, 8. Oktober 2009 22:06:10 schrieb Alan Stern:
    >
    > >
    > > On further thought, unthrottle should autoresume if the device is
    > > open and autosuspended (but it shouldn't do anything if the device is
    > > suspended). After all, the reason for the autosuspend may have been
    > > the lack of activity caused by the throttling.
    > >
    > > In practice this isn't likely to come up. It would be surprising if
    > > throttling lasted long enough to cause an autosuspend or if the core
    > > decided to throttle while the device was autosuspended and hence idle.
    >
    > So you say that throttle() should do an autopm_put?

    The way you've coded the sierra and option drivers, it's not necessary.
    Those drivers do an autopm_get_async during submission and an
    autopm_put_async after the completion of every output URB (and they
    update the last_busy time in the completion of every input URB). When
    the driver is throttled no URBs will be submitted, so the usage count
    will remain at 0 with no effort on the part of throttle().

    For other drivers that use the simpler "autoresume on tty install,
    autosuspend on tty cleanup" approach provided by usb-serial.c, the
    throttle routines obviously don't need to worry about runtime PM.

    Alan Stern



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