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    SubjectRe: New conflict message in latest GIT
    Hi Fabio,

    On Wed, 23 Jul 2008 21:50:24 +0200, Fabio Comolli wrote:
    > Hi.
    > On Wed, Jul 23, 2008 at 8:56 PM, Bjorn Helgaas <> wrote:
    > > On Tuesday 22 July 2008 12:56:36 pm Fabio Comolli wrote:
    > >> Linus' GIT tree 2.6.26-05752-g93ded9b shows this message:
    > >>
    > >> i801_smbus 0000:00:1f.3: PCI INT B -> GSI 19 (level, low) -> IRQ 19
    > >> ACPI: I/O resource 0000:00:1f.3 [0x18e0-0x18ff] conflicts with ACPI
    > >> region SMBI [0x18e0-0x18ef]
    > >> ACPI: Device needs an ACPI driver
    > >>
    > >> There is no equivalent in 2.6.26 or previous kernels.
    > >
    > > The "ACPI: I/O resource ... conflicts with ..." message was added by
    > > Thomas:
    > >;a=commitdiff;h=df92e695998e1bc6e426a840eb86d6d1ee87e2a5
    > >
    > > That conflict checking infrastructure was in 2.6.26, but Jean's
    > > change to make the i801_smbus driver use it didn't happen until
    > > about a week ago:
    > >;a=commitdiff;h=54fb4a05af0a4b814e6716cfdf3fa97fc6be7a32
    > >
    > > The message is telling us that the i801_smbus driver thinks it owns
    > > the 0x18e0-0x18ff region, but there's also an ACPI opregion that
    > > references that region. There's no coordination between ACPI and
    > > the i801_smbus driver, so there may be issues where nearly
    > > simultaneous accesses cause incorrect behavior, e.g,. one may
    > > read the wrong value from a temperature sensor. That, of course,
    > > can lead to more serious things like unintended machine shutdowns.
    > >
    > > I don't have any ideas about how to address this. I think Thomas's
    > > intent was to collect better information for unreproducible bugs.
    > > (Maybe this sort of conflict should even set a taint flag?)

    Yes, at this point these messages are informative only and displayed as
    a hint when investigating bug reports. In the long run, we might
    decide to grant exclusive access to the shared region to either ACPI or
    the native driver, or to setup a safe concurrent access mechanism.
    That's a long way to go though, due to the diversity of BIOSes out
    there and the fact that many of them declare opregions in bogus ways.

    > OK, I actually didn't even know what i801_smbus (i2c_801 I suppose)
    > was. It seems that my laptop has a super-IO chip which is detected by
    > lm-sensors as `Nat. Semi. PC87591 Super IO' which doesn't have a
    > driver and never will.
    > So, if I'm correct, this modules is totally useless for me and I
    > better compile it out. Am I correct?

    Yes you are. If you don't need i2c-i801 on this machine, best is to not
    build it or to prevent it from loading. Or you can boot with
    acpi_enforce_resources=strict to prevent the i2c-i801 driver from
    attaching to the device.

    I am a bit curious though, why ACPI would declare an opregion for a
    device that isn't used. Might be yet another case of BIOS copied from
    another machine and not cleaned up appropriately.

    Jean Delvare

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