Re: [PATCH 3/5] [pm] Respect the actual device power states in sysfs interface

Patrick Mochel
2006-02-20T18:08:36Z

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On Mon, 20 Feb 2006, Pavel Machek wrote:

> Hi!
>
> > > > > Compatibility is already restored.
> > > >
> > > > No, the interface is currently broken. The driver core does not
> > > > dictate
> > >
> > > There were two different interfaces, one accepted 0 and 2, everything
> > > else was invalid, and second accepted 0, 1, 2, 3.
> > >
> > > If you enter D2 on echo 2, you are breaking compatibility with 2.6.15
> > > or something like that.
> >
> > I don't see how this is true. If a process writes "2" to a PCI device's
> > state file, what else are sane things to do?
>
> In some kernel version (2.6.15, iirc), device entered D3 if you wrote
> "2" to state file, and there are programs out there that depend on
> it.

Like what?

> > You dropped the fundamental point, and I don't understand why you disagree
> > with it - the driver core should not be dictating policy to the downstream
> > drivers. It is currently doing this by filtering the power state that is
> > passed in via the "state" file.
>
> That's best we can do to stay compatible. Please introduce new file,
> and make states string-based.

You are still overlooking the point - the core should not be filtering the
values. It currently is, but it's trivial to fix. What is your issue with
that?

Thanks,

Pat