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    SubjectRe: RFC: ACPI/scsi/libata integration and hotswap
    On Tue, 13 Dec 2005 18:26:51 +0000
    Matthew Garrett <mjg59@srcf.ucam.org> wrote:

    > On Tue, Dec 13, 2005 at 10:14:17AM -0800, Randy Dunlap wrote:
    >
    > > 7. Most important: What good does the ACPI interface do/add?
    > > What I mean is that acpi_get_child() in scsi_acpi_find_channel()
    > > always returns a handle value of 0, so it doesn't get us
    > > any closer to determining the ACPI address (_ADR) of the SATA
    > > devices. The acpi_get_devices() technique in my patch (basically
    > > walking the ACPI namespace, looking at all "devices") is the
    > > only way that I know of doing this, but I would certainly
    > > like to find a better way.
    >
    > When the PCI bus is registered, acpi walks it and finds the appropriate
    > acpi handle for each PCI device. This is shoved in the
    > firmware_data field of the device structure. Later on, we register the
    > scsi bus. As each item on the bus is added, the acpi callback gets
    > called. If it's not an endpoint, scsi_acpi_find_channel gets called.
    > We're worried about the host case. The host number will correspond to
    > the appropriate _ADR underneath the PCI device that the host is on, so
    > we simply get the handle of the PCI device and then ask for the child
    > with the appropriate _ADR. That gives us the handle for the device, and
    > returning that sticks it back in the child's firmware_data field.
    >
    > At least, that's how it works here. If acpi_get_child always returns 0
    > for you, then it sounds like something's going horribly wrong. Do you
    > have a copy of the DSDT?

    Thanks for the explanation.
    The 136 KB DSDT is at:
    http://www.xenotime.net/linux/SATA/acpitbl.out .

    ---
    ~Randy
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