On Tue, 24 Jun 2008, Ingo Molnar wrote:
> * Vegard Nossum <vegard.nossum@xxxxxxxxx> wrote:
>
> > On Fri, Jun 20, 2008 at 11:27 PM, Vegard Nossum <vegard.nossum@xxxxxxxxx> wrote:
> > > So I guess this function, pnpbios_init() needs the check as well. In
> > > fact, it has this:
> > >
> > > #ifdef CONFIG_PNPACPI
> > > if (!acpi_disabled && !pnpacpi_disabled) {
> > > pnpbios_disabled = 1;
> > > printk(KERN_INFO "PnPBIOS: Disabled by ACPI PNP\n");
> > > return -ENODEV;
> > > }
> > > #endif /* CONFIG_ACPI */
> > >
> > > ...I guess that should be changed to say if (acpi_disabled ||
> > > pnpacpi_disabled)? Or... I don't understand the purpose of the
> > > original test. But it seems to be there since the beginning of time
> > > (or, well, v2.6.12-rc2).
> >
> > Nope. I found the introduction of the change in the historical git repository:
> >
> > commit 4723ebe898a32262ed49fe677897ccea47e72ff4
> > Author: Adam Belay <ambx1@xxxxxxxxxx>
> > Date: Sun Oct 24 15:07:32 2004 -0400
> >
> > [PNPBIOS] disable if ACPI is active
> >
> > As further ACPI pnp functionaility is implemented it is no longer
> > safe to run ACPI and PNPBIOS concurrently.
> >
> > We therefore take the following approach:
> > - attempt to enable ACPI support
> > - if ACPI fails (blacklist etc.) enable pnpbios support
> > - if ACPI support is not compiled in the kernel enable pnpbios support
> >
> > Signed-off-by: Adam Belay <ambx1@xxxxxxxxxx>
> >
> > and now I understand the purpose of the check; pnpbios does not depend
> > on ACPI; ACPI/pnpacpi is incompatible with pnpbios.
>
> wow, rather old bug - i guess lockdep made it more visible.
No, that commit was not a bug, it was correct, and still is,
for pnpACPI and pnpBIOS must be mutually exclusive.
The thing that changed was the RTC specific code.
-Len
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