On Thu, 2008-04-17 at 16:44 +0200, Andi Kleen wrote: > > > > For drivers that can alter their descriptor types, we have this > > function: > > > > dma_get_required_mask() > > Are you sure we have it? It seems to be in drivers/base/platform.c > conditional on ARCH_HAS_DMA_GET_REQUIRED_MASK, but according to my > grep no architecture ever sets that flag. Yes ... positive. That's the default and correct implementation based on the largest addressable physical memory. > I don't think it would be very hard to implement on x86 at least, > mind you. Just nobody seems to have done it so far. Really, only machines with IOMMUs that want to restrict this need implement it. Current safety is predicated on the assumption that no architectures with IOMMUs never return bus physical addresses above memory physical. If that's not true, then they *have* to implement this. For all others its an optimisation to return a more restricted range. James -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
