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    SubjectRe: [PATCH 5/5] ACPI: Tie ACPI backlight devices to PCI devices if possible
    Date
    On Monday, February 07, 2011, Matthew Garrett wrote:
    > On Mon, Feb 07, 2011 at 02:32:35PM -0700, Bjorn Helgaas wrote:
    >
    > > I'm not familiar with video devices, but I agree, this situation does
    > > feel broken. Is it the case that there's a PCI device as well as an
    > > ACPI namespace Device for the same piece of hardware? If so, I assume
    > > the reason for the ACPI Device is to have a "standard" interface to
    > > a platform knob like backlight control.
    > >
    > > In that case, it seems like we should rely on PCI for enumeration and
    > > driver binding, have some sort of hook the PCI driver could use to
    > > twiddle that knob (using the ACPI methods), and make the ACPI Device
    > > ineligible for driver binding. In other words, it sounds like part
    > > of the problem is that we have two drivers binding to what's really
    > > a single piece of hardware.
    >
    > Part of the problem is that ACPI video devices aren't inherently PCI
    > devices.

    To me, this really isn't about video devices. The problem is that objects
    of type struct acpi_device are treated _differently_ depending on the context.

    In the meantime I've reviewed the code a bit and noticed that there's a
    parent pointer in struct acpi_device, which basically duplicates the device
    tree dependency, so it looks like the embedded dev in struct acpi_device is
    really redundant.


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