Re: question on flushing buffers and spinning down disk

[Oliver Neukum <oliver@neukum.org>]

Am Montag 24 September 2007 schrieb Alan Stern:
> On Mon, 24 Sep 2007, Oliver Neukum wrote:
> 
> > > suspend.  The PM and driver cores don't include _any_ provision for
> > > runtime suspend; it has to be managed separately by each subsystem.
> > 
> > There we have a problem. We'd have to solve it for each subsystem transition.
> > Storage has this type of children, other devices will have to care for other
> > types of child devices. If we have a device tree, we should use it.
> 
> It sounds like you want to add the equivalent of
> usb_autopm_get/set_device() and usb_autopm_get/set_interface() into the

That would be an ideal solution, but it is not necessary to solve this
problem.

> driver model.  But it would not be appropriate, since other subsystems
> don't have the same kinds of runtime power levels as USB does.

But we don't bother when suspending the whole system. So why not simply
walk the subtrees under a USB device? Let the subsystem choose what
depth of sleep to use.
 
> There may be no way of getting around the need for specialized 
> communication methods between subsystems for runtime PM.

That's a lot of code duplication and should be a solution of last resort.

	Regards
		Oliver

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