On Sat, 25 Sep 2004, David Brownell wrote:

> On Friday 24 September 2004 12:13 pm, Alan Stern wrote:
> > 
> > What I've learned from this discussion is that there needs to be 
> > another PM device state, or really a pseudo-state.  Let's call it 
> > PM_SUSPEND_IDLE. 
> 
> There do need to be activity states as well as power states,
> and IDLE could be an activity state.  It'd be one that could
> be visible to system PM activities like "suspend to disk",
> which needs to quiesce all activities THEN write an image
> to disk (activity!) and suspend all the hardware.

[Sigh]

In fact there are three distinct but closely related concepts involved,
and they all need to be handled simultaneously in some reasonably way.  
They are: power level, IRQ/DMA enabled (or activity level if you prefer),
and wakeup enabled.  These things are almost independent (except that
wakeup is meaningless in the full-power state).  But they are tied
together in bizarre ways, such as not being able to change the wakeup
enable setting if the device isn't at full power.  Or the fact that at 
some points in the device tree, wakeup requests are transformed into 
interrupt requests.

Alan Stern



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