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    SubjectRe: [PATCH v3] uio/pdrv_genirq: Add OF support
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    On Tuesday 19 April 2011, John Williams wrote:
    > OK, so let's talk about this interface. As I see it, it must be able
    > to handle bind per-instance, not per compatibility.

    Yes.

    > For example, we make systems with multiple, identical timers. One
    > will be used as the system timer, the others need to be (optionally)
    > bound to generic UIO.
    >
    > Therefore, it's not OK to just do
    >
    > echo "vendor,device" >> /sys/class/something/generic-uio/compatlist
    >
    > or whatever, as this would bind all instances matching vendor,device.
    >
    > So, the question I have is, how to handle bind per-instance?
    >
    > I can accept that the generic-uio idea is permanently blocked, but
    > please can we have some concrete suggestions on an approach that would
    > be acceptable?

    I think nobody has had a good idea so far, unfortunately. It would
    be nice if you could research how libusb, vfio and qemu pci passthrough
    work. Hopefully one of these uses a method that we can do here, too.

    > > In the mean time, explicitly modifying the match table is an okay
    > > compromise.
    >
    > My mind is still boggling that in this day and age it could possibly
    > be preferred to modify code, instead of a data structure. However,
    > clearly this is a lost cause!

    It's preferred to do a local modification to a single kernel build over
    introducing an interface that we have to maintain compatibility with
    when we already know we don't want it.

    Arnd


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