[linux-pm] [RFD] Automatic suspend

[Oliver Neukum]

Am Wednesday 18 February 2009 15:51:58 schrieb Arjan van de Ven:
> On Wed, 18 Feb 2009 09:53:48 +0100
> Oliver Neukum <oliver at neukum.org> wrote:
> 
> > Am Wednesday 18 February 2009 00:26:53 schrieb Rafael J. Wysocki:
> > > > Another possibility is to set up independent runtime PM for the
> > > > transport and the device.  This means allowing the possibility
> > > > that the transport is suspended while its child (the device) is
> > > > not.  This is a little simpler (there's only one idle-timeout per
> > > > device, since the link is treated as an independent device), but
> > > > it violates the principle of never suspending a parent while
> > > > there is an active child.
> > > 
> > > Well, I think the first approach would be better.
> > 
> > I am afraid it wouldn't be. How do you deal with shared transports?
> > 
> 
> realistically, something like this you need to design like this
> Step 1) Assume the hardware is smart and can do this for you on the fly,
>         but it might need guidance.
>         (For many busses there are platforms that do this)
> Step 2) For hardware that is not smart, emulate the smartness in the
>         driver, with help of the subsystem. These two together have
>         the right knowledge to make such decisions.

But the transport and the driver may be in different subsystems, e.g.
usb storage.

	Regards
		Oliver