Re: [RFC][PATCH 2/3] PM / sleep: Mechanism to avoid resuming runtime-suspended devices unnecessarily

Alan Stern
2014-05-19T19:53:58Z

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".

Alan Stern