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    SubjectRe: [patch 2/5] Staging: vme: add VME userspace driver
    Martyn Welch wrote:
    > suggest if you want something more complex that allows the user to just
    > pick a location/size and not worry about windows at all

    That's exactly the whole point. I think each bridge should manage
    its resources; putting this on the upper layer would mean the
    layer should have a mechanism of 'discovering' what the bridge
    can/can't do. Anyway this could be revisited later.
    I'm preparing a patch for this.

    >> - Most accesses are 32-bit accesses. Treating all of them
    >> as 64-bit accesses would decrease performance for most of
    >> them--which happen to be 32-bit.
    > I'm not - I'm storing them as 64-bit values, which they are, in the
    > structures used in *software*. These are then split *when* a write to
    > the hardware registers is required. Similarly, when the registers are
    > occasionally read they are combined and stored as a 64-bit value. This
    > simplifies all *software* checking and manipulation. By storing these as
    > 2 32-bit values every driver that uses the VME core will need to convert
    > pci addresses, vme addresses and counts to 2 32-bit values. That is
    > madness.

    I agree with you on that's painful for doing 64-bit accesses.
    However I'm still not convinced on the performance side (I mean
    software), since most of the time the upper 32bits will be empty.
    Will have a look though.


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