Messages in this thread | | | Date | Thu, 28 Apr 2011 14:19:28 +0100 | From | Russell King - ARM Linux <> | Subject | Re: [RFC] ARM DMA mapping TODO, v1 |
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On Thu, Apr 28, 2011 at 03:02:16PM +0200, Arnd Bergmann wrote: > I think the misunderstanding is that you are saying we need the flag > in dma_map_ops because you prefer to keep the cache management outside > of the individual dma_map_ops implementations. > > What I guess Jörg is thinking of is to have the generic IOMMU version > of dma_map_ops call into the architecture specific code to manage the > caches on architectures that need it. That implementation would of > course not require the flag in dma_map_ops because the architecture > specific callback would use other ways (hardcoded for an architecture, > or looking at the individual device) to determine if this is ever needed. > > That is also what I had in mind earlier, but you argued against it > on the base that putting the logic into the common code would lead > to a higher risk of people accidentally breaking it when they only > care about coherent architectures.
You still need this same cache handling code even when you don't have an iommu. I don't see the point in having a dma_ops level of indirection followed by a separate iommu_ops level of indirection - it seems to me to be a waste of code and CPU time, and I don't see why its even necessary when there's a much simpler way to deal with it (as I illustrated). -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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