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

Pavel Machek
2006-02-20T18:10:40Z

On Po 20-02-06 10:08:36, Patrick Mochel wrote:
>
> 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?

Search archives. Some PCMCIA, IIRC.

> > > 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?

That you are breaking compatibility in middle of 2.6 series. And very
close to 2.6.16 at that.
Pavel
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