Re: newbus ioport usage

From: M. Warner Losh (imp_at_bsdimp.com)
Date: 01/27/04

  • Next message: Nate Lawson: "Re: newbus ioport usage" 
    Date: Tue, 27 Jan 2004 15:09:36 -0700 (MST)
To: nate@root.org

    In message: <20040127133251.W75080@root.org>
                Nate Lawson <nate@root.org> writes:
    : On Tue, 27 Jan 2004, M. Warner Losh wrote:
    : > In message: <20040127125547.G74774@root.org>
    : > Nate Lawson <nate@root.org> writes:
    : > : Ok, let me propose a design and I'd appreciate your comments. The probe
    : > : routine for acpi_sysresource will stay the same. The attach will allocate
    : > : the resources to its parent device (acpi0).
    : > :
    : > : acpi0 will make this set of resources available to its children via a
    : > : flag included with bus_alloc_resource, say ACPIDEV_REQUEST. If
    : > : acpi_resource_alloc finds a range already has that flag set, it will
    : > : refuse the request. Otherwise, it will release that range and then
    : > : immediately allocate it to the child.
    : >
    : > That seems overly convoluted. Why not just allocate it in acpi0? If
    : > a driver requests something that acpi0 has allocated, it assigns it to
    : > the child and takes it out of its resource manager. If not, then it
    : > passes things up a level in the tree. No special flags needed,
    : > although acpi does get a little more complicated. This will ensure
    : > that the resources are owned by someone, and can easily be delegated.
    : > These resource ranges are there to be used by acpi, and only acpi.
    :
    : So acpi0 would do a resource_list_delete for the given resource if it's in
    : the list and then perform the alloc request. This would then succeed
    : since no one owns the resource at that point. Once it succeeds, the child
    : owns the range and it can't be stolen. And I guess when the child
    : releases the range, acpi0 can reclaim all such resources. I wouldn't want
    : a pccard device plugged in later to grab the IO ports after a child
    : temporarily releases them (say while the ACPI Performance cpufreq driver
    : is unloaded and then reloaded).

    Right, that's why it would delegate the resource. This implies that
    when the delegation is released, it would go back to being owned by
    acpi0.

    : > There's nothing magical about the acpi_sysresource device, and it can
    : > be relegated to the scrap-heap of history if needed.
    :
    : Well, the way we find out about the resources is through a pseudo-device
    : with a PNPID. So it makes sense to use the normal device discovery method
    : to find these resources. This leads me to do the allocation for the
    : parent by the acpi_sysresource0 attach method.

    This gets ugly. The reason that I suggested not doing the discovery
    this way is because you want to allocate *ALL* resources up front
    before giving any to any children. pci has issues with this right now
    that I'm working to fix.

    Warner
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  • Next message: Nate Lawson: "Re: newbus ioport usage"

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