minimum guaranteed alignment of dma_alloc_coherent?
timur at freescale.com
Sat Feb 5 11:14:44 EST 2011
Is there any official statement on what the minimum alignment is for
memory returned by dma_alloc_coherent? I know that since it uses a
page allocator to do the actual allocation, that the memory is page
aligned (at least on PowerPC). Is this something I can rely on?
Would anyone have a complaint if I did this:
vaddr = dma_alloc_coherent(dev, ssize, &paddr, GFP_DMA | __GFP_ZERO);
BUG_ON(paddr & (alignment - 1));
'alignment' will always be 32 or less.
The reason I ask is that I currently have code that ensures an
alignment, but it does so by allocating extra memory, and that seems
On a side note, do I really need to pass GFP_DMA when calling
dma_alloc_coherent? That seems redundant, but I don't see the code
force it to be set. Should it be forced on?
Linux kernel developer at Freescale
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