Re: [PATCH 4/4] ACPI PCI slot detection driver

[Kenji Kaneshige]

Hi,

> My interpretation of this is that if Alex's driver scans the Fujitsu
> machine and calls _STA on one of the slots and gets Bit 0 (present) and
> Bit 3 (functioning) set, then it is ok to enumerate it's children and
> evaluate _ADR and _SUN for the children.  If they are returning 1023,
> that would mean you should not evaluate the children of that object
> since the functional bit is not set.  Is this correct?

Yes, it is one of the reason we should evaluate _STA before evaluating
_STA. Maybe you're referring '1023' as a _STA value on Fujitsu server,
but it is _SUN value. If a driver evaluate _SUN even if its corresponding
_STA is 0, Fujitsu firmware returns '1023' as a _SUN value. The reason why
Fujitsu firmware is doing so is because ACPI doesn't provide a way to
return errors in this situation.

> If that is the case, I would say that Alex's driver needs to obey the
> spec - or else if the this is allowed in an earlier version of the spec
> then he needs to check for the version of the spec that was implemented
> and make some different rules for that.

Yes. I thought it's a goot idea too. But it doesn't work because ACPI2.0
based HP's machines also want Alex's driver to ignore _STA.

Thanks,
Kenji Kaneshige


Kristen Carlson Accardi wrote:
> On Tue, 11 Mar 2008 22:10:40 +0900
> Kenji Kaneshige <kaneshige.kenji@xxxxxxxxxxxxxx> wrote:
>
> > Hi Alex-san,
> >
> > Alex Chiang wrote:
> > > > > It wasn't the IBM machine that was breaking; it was Fujitsu. They
> > > > > were returning an error code (the numerical value 1023) when I
> > > > > called the _SUN method on a slot object that existed in the ACPI
> > > > > namespace but was not present (as reported by the _STA method).
> > > > > By the time I got that error report, I'd already dropped the
> > > > > duplicate name detection code, and was letting the kobject
> > > > > infrastructure warn about duplicate names because for my test
> > > > > cases, refcounting was a better solution.
> > > > > [Kenji-san from Fujitsu seemed to be ok with the progress I'd
> > > > > made at the time, he can speak up if he's changed his mind ;)]
> > > > Unfortunatelly, I have not tried the new version of slot detection
> > > > driver because of the lack of test environment. Maybe we need more
> > > > several days to wait for test environment. 
> > > > BTW, does the new one fixes the issue I reported before? I could
> > > > not find it in the changelog. IIRC, this issue was difficult to
> > > > solve because the root cause of this issue is from the difference
> > > > of interpretation of ACPI spec between HP and Fujitsu (I still
> > > > don't think it's a good idea to evaluate _SUN for the device
> > > > object whose _STA is 0).
> > > It looks like we disagree on how to interpret the spec (IBM
> > > machines interpret the spec the same way HP machines do).
>
> OK, let me see if I can understand what the issue is here.  Please
> correct me if I'm wrong.  The debate is about whether or not it is
> legitimate to call _SUN if _STA indicates that the device is not
> present and functional.  I've checked ACPI 3.0b, and from what I've
> read, you may not evaluate _SUN until _INI is called.  And _INI should
> not be called unless _STA indicates that a device is present and
> functional.
>
> "OSPM evaluates the _STA object before it evaluates a device _INI
> method. The return values of the Present and Functioning bits
> determines whether _INI should be evaluated and whether children of the
> device should be enumerated and initialized. See section 6.5.1, â_INI
> (Init)â."
>
> My interpretation of this is that if Alex's driver scans the Fujitsu
> machine and calls _STA on one of the slots and gets Bit 0 (present) and
> Bit 3 (functioning) set, then it is ok to enumerate it's children and
> evaluate _ADR and _SUN for the children.  If they are returning 1023,
> that would mean you should not evaluate the children of that object
> since the functional bit is not set.  Is this correct?
>
> If that is the case, I would say that Alex's driver needs to obey the
> spec - or else if the this is allowed in an earlier version of the spec
> then he needs to check for the version of the spec that was implemented
> and make some different rules for that.
>
> Thanks for the clarification,
> Kristen


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