Re: [PATCH 4/4] USB: export autosuspend delay in sysfs

Am Montag, 26. Februar 2007 18:37 schrieb Alan Stern:
> > - don't do an immediate suspend independent of autosuspend
> 
> Why not?  In extreme cases the user can force an immediate suspend by 
> doing suspend-to-RAM anyway.  This merely preserves the capability we are 
> about to lose when the power/state attribute disappears completely.

Arent we removing that attribute among other things precisely because
this capability violates the power tree requirements?

> > > Add a new power/suspended attribute.  Writing 1 will always try to suspend
> > > immediately (_not_ an autosuspend!) and writing 0 will always resume
> > > immediately (but will start the autosuspend timer).
> > 
> > This is problematic, as it is a totally new code path.
> 
> No it isn't.  It's the code path used for traditional
> suspend-to-{RAM,disk} and also used by power/state.

STR/D freeeze user space, thus making additional guarantees we wouldn't
meet. power/state is being obsoleted.
 
> > > BTW, note that an autosuspend request is different from a plain old
> > > suspend request.  Autosuspend will fail if an interface requires
> > > remote-wakeup capability but remote wakeup is disabled, whereas a regular
> > > suspend won't fail.
> > 
> > Yes, that too. It makes that even more asymmetric. We wake up on demand
> > in only one direction.
> 
> I don't know what you mean.  We _always_ wake up on demand.  What's
> asymmetrical about that?

We wake up for output. We suspend even if we can't wake up for input.

> >  If you want such an interface I'd suggest that it mean
> > that a device stay suspended until the user says so.
> 
> No.  One more time:
> 
>                 WE ALWAYS WAKE UP ON DEMAND!

Why? Repeating the assertion doesn't make it any more logical.
 
> If the user really wants a device to suspend and not wake up, he can take
> more drastic action.  Just don't send it any more demands.  Unbind it from
> its driver.  Unplug it -- and that would save even more power!

(Apart from the interesting question of how to unplug a touchpad built
into a laptop)

If we want that, than again I don't see why you want to suspend "in between"
autosuspend and full system suspend. It should be enough to suspend
immediately if the driver has agreed to autosuspension.

	Regards
		Oliver

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