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    SubjectRe: [PATCH] ACPI: don't walk tables if ACPI was disabled


    On Tue, 24 Jun 2008, Ingo Molnar wrote:

    > * Vegard Nossum <vegard.nossum@gmail.com> wrote:
    >
    > > On Fri, Jun 20, 2008 at 11:27 PM, Vegard Nossum <vegard.nossum@gmail.com> 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@neo.rr.com>
    > > 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@neo.rr.com>
    > >
    > > 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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