On Mon, 2008-02-25 at 17:54 -0500, Jeff Garzik wrote:
> Matthew Wilcox wrote:
> > On Mon, Feb 25, 2008 at 11:40:35PM +0100, Andi Kleen wrote:
> >>> (I must have fixed it somehow because it works on parisc, which is most
> >>> unforgiving of drivers which do DMA without the DMA API).
> >> At least on x86 the DMA API cannot do ISA bouncing.
> >
> > You're saying that if I set a 24-bit DMA mask, and then do a
> > pci_alloc_coherent(), x86 might hand me back something that's not
> > accessible? That would be just broken.
>
> Indeed.
It's doing the right thing (from pci-dma_32.c):
void *dma_alloc_coherent(struct device *dev, size_t size,
dma_addr_t *dma_handle, gfp_t gfp)
[...]
if (dev == NULL || (dev->coherent_dma_mask < 0xffffffff))
gfp |= GFP_DMA;
ret = (void *)__get_free_pages(gfp, order);
Which correctly allocates the region.
James
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