From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: Sat, 22 Sep 2012 07:46:40 +1000
Right, but on ppc, GFP_DMA is a nop (no separate ZONE_DMA, or rather all
of memory is ZONE_DMA). It's always been like that afaik.
We could support ISA device limited addressability using the iommu but
that would involve a map/unmap type API (which I remember we did support
in the old days by passing NULL to pci_map_*, but we dropped that along
the way).
I think I'm going to just end up restricting this driver to X86
as was originally suggested.
There seems to be no real consistent Kconfig protection for users
of isa_virt_to_bus() and friends.
We know that ISA_DMA_API doesn't do it, and ISA doesn't do it either
as powerpc also allows that to bet set for CHRP and friends.
Thanks.