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    SubjectRe: [RFC][PATCH 2/3] PM / sleep: Mechanism to avoid resuming runtime-suspended devices unnecessarily
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    On Monday, May 19, 2014 03:53:58 PM Alan Stern wrote:
    > On Mon, 19 May 2014, Jacob Pan wrote:
    >
    > > > Wouldn't that go a bit too far? It seems to be based on the
    > > > assumption that all devices having no ->prepare() callback can be
    > > > safely left in runtime suspend over a system suspend/resume cycle,
    > > > but is that assumption actually satisfied for all such devices?
    > > >
    > > yes, I agree it is risky though i don't see problems with my limited
    > > testing. But on the other side, it is too strict.
    > > I also tried adding .prepare( return 1;) to usb_ep_device_type pm ops,
    > > that didn't work either. The reason is that ep devices don't support
    > > runtime pm (disable_depth > 0). I think in this case ignore_children
    > > flag should be the right indicator to ignore pm_runtime_suspended()?
    >
    > Maybe it would be better to add a new flag that means "This is a
    > virtual device and the PM core can ignore it completely".

    I like that idea. :-)

    Rafael



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