Am Freitag, 26. Januar 2007 16:28 schrieb Alan Stern:
> On Fri, 26 Jan 2007, Oliver Neukum wrote:
>
> > Am Donnerstag, 25. Januar 2007 20:55 schrieb Alan Stern:
> > > Now something we _could_ use is an API allowing userspace to do runtime
> > > suspend/resume of USB devices. The /sys/devices/.../power/state thing is
> > > deprecated and will be removed soon. I posted a patch for this purpose
> > > some time ago:
> > >
> > > http://marc.theaimsgroup.com/?l=linux-usb-devel&m=115151191222054&w=2
> > >
> > > Greg said that it wasn't needed yet. But eventually something like it
> > > _will_ be needed.
> >
> > Upon further thought, why yet another USB specific mechanism?
>
> How quickly they forget... :-)
I wish I had forgotten about all that.
> Remember all those endless discussions on the linux-pm list about runtime
> PM and the PM sysfs API? In the end people agreed that
> /sys/devices/.../power/state was no good. People also agreed that runtime
> power management is inherently device-specific (or at the very least,
> bus-specific) and should not be constrained to fit in a single inflexible
> mold.
Specifically it was decided that the existing interface is crap. There was
never a decision what was to replace that.
IIRC at one time we had an interface that exported the supported power
states.
> For example, USB devices have two power states: on and suspended. PCI
> devices can have four states: D0 - D3hot. Other devices have other sets
> of states and other parameters to control them (which power lines and
> which clocks should be gated on, etc.).
>
> In short, our suspend/resume API _has_ to be USB-specific.
We were talking about autosuspend. Which is strictly speaking not about
how to suspend, but under which conditions to suspend. Do you want to
move it to power core or not?
Unfortunately I am not not ready to come up with the interface that will
make everybody happy ;-). I just see the discrepancies.
Regards
Oliver
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