Messages in this thread | | | Date | Thu, 9 Apr 2009 06:15:07 +0900 | Subject | Re: [PATCH 4/7] swiotlb: Allow arch override of address_needs_mapping | From | FUJITA Tomonori <> |
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On Wed, 8 Apr 2009 15:56:32 -0500 Kumar Gala <galak@kernel.crashing.org> wrote:
> > 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.
ia64 and x86_64 use swiotlb but neither need this function. And neither need any above __weak. They were added for dom0 support. Yeah, swiotlb is much cleaner and better if we don't add dom0 support.
About this patch, I think that we could do better. What we need to do is allowing each architectures to have is_buffer_dma_capable().
I'm doing the dma_mapping_ops unification. I think that adding something like is_buffer_dma_capable to dma_map_ops struct is cleaner. Then we don't need this __weak function. But this patch is fine by me for now.
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