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To: David Brownell <david-b@pacbell.net>
cc: James Bottomley <James.Bottomley@SteelEye.com>,
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Subject: Re: [PATCH] generic device DMA (dma_pool update) 
In-Reply-To: Message from David Brownell <david-b@pacbell.net> 
   of "Tue, 31 Dec 2002 11:29:35 PST." <3E11F01F.7040205@pacbell.net> 
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Date: Tue, 31 Dec 2002 13:50:54 -0600
From: James Bottomley <James.Bottomley@steeleye.com>
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david-b@pacbell.net said:
> You didn't make anything store or return the dma_addr_t ... that was
> the issue I was referring to, it's got to be either (a) passed up from
> the very lowest level, like the pci_*() calls assume, or else (b)
> cheaply derived from the virtual address.  My patch added slab support
> in common cases where (b) applies. 

That's fairly simply done as part of the wrappers: The allocator stores the 
vaddr, paddr and size in a hash table.  Thus, the paddr can be deduced when 
kmem_cache_alloc is called by the allocation wrapper using the linearity 
property.

I've got to say though that the most sensible course of action is still to 
generalise pci_pool, which can be done easily and safely.  I think replacing 
it with a slab based scheme is probably a 2.7 thing.

James




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