Re: [linux-pm] [patch update 2 fix] PM: Introduce core framework for run-time PM of I/O devices

From: Rafael J. Wysocki
Date: Mon Jun 22 2009 - 11:27:24 EST

On Monday 22 June 2009, Alan Stern wrote:
> On Sun, 21 Jun 2009, Rafael J. Wysocki wrote:
> > > Seriously, there _are_ places where drivers get bound to device before
> > > those devices are registered. This happens for example in USB when a
> > > bunch of related interfaces are present in the same physical device.
> > > When the first interface is registered, its driver binds itself to all
> > > the others even though they haven't been registered yet.
> >
> > Well, the suspend functions could be protected against that under the
> > assumption that no suspend is possible for resume_counter = 0 (then, the "good
> > to go" value would be -1).
> >
> > Still, the resume functions start from acquring a spinlock, which is not going
> > to work if that spinlock is uninitialized.
> The initialization needs to be improved. Most of the code in
> pm_runtime_init() should be called from device_pm_init(), and the rest
> should be moved into a separate pm_runtime_add() routine to be called
> from device_pm_add().


In that case, I think, the initialization of the spinlock and resume_counter
can be put into the thing called by device_pm_init().

> One of the things pm_runtime_add() could do is change the status from

If the status is initially (ie. at the device_pm_init() point) RPM_ACTIVE and
resume_couter is initially 1, what are we going to need RPM_UNREGISTERED for?

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