most of the PCI alpha's support scatter gather in the chipset. ie you can
dynamically setup multiple bus->phys windows in the chipset.
so you could map any part of pci bus address to anywhere in physical space.
With multiple windows you could even map a contigious pci bus space to a
fragmented range of physical addresses.
Tru64 uses this for scatter gather support, even to 4GB+ phys addresses.
However linux doesn't use this feature at all. On linux we just setup two
2GB static mappings.
> In this situation we simply have to say this device does not work in
> this box and not allow it to be initialized.
>
> Ingo> probably the right solution is to introduce an Alpha-specific
> Ingo> DMA24BIT zone?
>
> Hmmm, there are several devices out there that will only do 24bit,
> 30bit and 31bit DMA respectively - we need a generic solution I think.
>
support for the 21172/21174 style hardware scatter gather would be nice and
generic.. :)
> Jes
paul jakma
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