Re: [PATCH] gurantee DMA area for alloc_bootmem_low() ver. 2.

On Tue, 2005-08-09 at 14:15 -0700, Mike Kravetz wrote:

On Tue, Aug 09, 2005 at 08:11:20PM +0900, Yasunori Goto wrote:

quoted

I modified the patch which guarantees allocation of DMA area
at alloc_bootmem_low().

I was going to replace more instances of __pa(MAX_DMA_ADDRESS) with
max_dma_physaddr().  However, when grepping for MAX_DMA_ADDRESS I
noticed instances of virt_to_phys(MAX_DMA_ADDRESS) as well.  Can
someone tell me what the differences are between __pa() and virt_to_phys().

At least one is that virt_to_phys()'s argument is usually 'volatile'
while __pa() is not.  This, of course, varies from arch to arch. 

If somebody wants to go and rip __pa() out from all of the arches, I
won't be especially sorry :)

Actually, it would be nice to have one arch-generic version which is
just the usual (vaddr - PAGE_OFFSET).  That would probably take care of
80% of the individual implementations.

-- Dave

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