Re: DMA memory limitation?

[Alan Cox]

> A problem arises on 64 bit platforms (such as IA64) if your PCI card is only 32bit (can
> address the first 4G) and you don't wan't to use bounce buffers. If you use GFP_DMA on

GFP_DMA is ISA dma reachable, Forget the IA64, their setup is weird and 
should best be ignored until 2.5 as and when they sort it out.

> bounce buffers are needed. On Alpha GFP_DMA is not limited at all (I think). Correct me if

Alpha has various IOMMU facilities

> I'm wrong, but I really think there should be a general way of allocating memory that is
> 32bit addressable (something like GFP_32BIT?) so you don't need a lot of #ifdef's in your
> code.

No ifdefs are needed

	GFP_DMA - ISA dma reachable
	pci_alloc_* and friends - PCI usable memory