[parisc-linux] ZONE_DMA

[Alan Cox]

> I'm not familiar with the hardware problem here.  Must EISA cards be
> restricted to a certain part of the address space?  I can glean from

EISA on PC can hit the full 32bits. DMA is meant to indicate the 16Mb lowest
memory segment that ISA can hit (which may not be at 0 depending on the box)

> the source that ISA cards are restricted to a 16MB address space --
> are we going to support ISA cards?

Some PCI cards have the same limit 8)

> I presume that no machine which supports ISA cards has an IOMMU that is
> capable of mapping a chunk of higher ram into the 16MB bus address space.

Some Alpha's probably can but we don't support that. The pci side API
pci_alloc_consistent does