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Cc: linux-kernel@vger.kernel.org, mingo@elte.hu, jeremy@goop.org,
       fujita.tomonori@lab.ntt.co.jp, ian.campbell@citrix.com,
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From: Kumar Gala <galak@kernel.crashing.org>
To: Christoph Hellwig <hch@infradead.org>
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Subject: Re: [PATCH 4/7] swiotlb: Allow arch override of address_needs_mapping
Date: Wed, 8 Apr 2009 15:56:32 -0500
References: <1239199761-22886-1-git-send-email-galak@kernel.crashing.org> <1239199761-22886-2-git-send-email-galak@kernel.crashing.org> <1239199761-22886-3-git-send-email-galak@kernel.crashing.org> <1239199761-22886-4-git-send-email-galak@kernel.crashing.org> <1239199761-22886-5-git-send-email-galak@kernel.crashing.org> <20090408203823.GA14985@infradead.org>
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On Apr 8, 2009, at 3:38 PM, Christoph Hellwig wrote:

> On Wed, Apr 08, 2009 at 09:09:18AM -0500, Kumar Gala wrote:
>> From: Becky Bruce <beckyb@kernel.crashing.org>
>>
>> Some architectures require additional checking to determine
>> if a device can dma to an address and need to provide their
>> own address_needs_mapping..
>
> Shouldn't we just move it completely to the arch?  I think that ia64  
> and
> x86 currently use the same one is more of an accident.

It seems like the swiotlb code uses __weak for a number of things:

lib/swiotlb.c:void * __weak __init swiotlb_alloc_boot(size_t size,  
unsigned long nslabs)
lib/swiotlb.c:void * __weak swiotlb_alloc(unsigned order, unsigned  
long nslabs)
lib/swiotlb.c:dma_addr_t __weak swiotlb_phys_to_bus(struct device  
*hwdev, phys_addr_t paddr)
lib/swiotlb.c:phys_addr_t __weak swiotlb_bus_to_phys(struct device  
*hwdev, dma_addr_t baddr)
lib/swiotlb.c:void * __weak swiotlb_bus_to_virt(struct device *hwdev,  
dma_addr_t address)
lib/swiotlb.c:int __weak swiotlb_arch_address_needs_mapping(struct  
device *hwdev,
lib/swiotlb.c:int __weak swiotlb_arch_range_needs_mapping(phys_addr_t  
paddr, size_t size)

instead of #ifndef HAVE_ARCH_<FOO>.  Not sure if there is a historical  
reason for that.

- k
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