Re: [linux-pm] Power management for SCSI

From: Alan Stern
Date: Fri Aug 22 2008 - 18:15:05 EST


On Fri, 22 Aug 2008, Pavel Machek wrote:

> Hi!
>
> > > - suspending has side effects
> >
> > I'm not sure what you mean by that. Suspension always has side effects
> > of one kind or another.
> >
> > > Suspension in USB has always side effects. That's not true for other
> > > subsystems.
> >
> > Name one. At the very least, suspending a device means you can't use
> > it again without first calling the driver's resume method. That's a
> > side effect.
>
> IDE, actually. I don't think it is relevant, but you can do hdparm -y,
> and it will automatically spin up when you try to talk to it next
> time.

It's a matter of definitions... "hdparm -y" doesn't call the driver's
suspend method, so in some sense it isn't truly a suspend.

But it's true that some systems can power down more or less
transparently (with restart latency as the only visible side effect).

Alan Stern

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