From: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> Date: Fri, 21 Sep 2012 08:22:44 +1000 > Hrm, that's ancient gunk, I'll have to dig. We potentially can support > ISA devices DMA'ing from an ISA bridge... but via the iommu, which means > isa_virt_to_bus is a non-starter. > > But then, do we really care ? IE. Is there single device that actually > requires ISA_DMA_API and that is expected to work on any currently > supported powerpc hw ? :-) > > We don't even support PReP anymore, so that leaves us with what ? ISA_DMA_API implies a fixed window of addresses which are <= 32-bits on the bus, which is a hardware requirement of these devices. isa_virt_to_bus() goes to that physical address, and the expection is that you use GFP_DMA and thus the physical addresses fit inside of an unsigned int. isa_virt_to_bus() basically amounts to a virt-->phys plus a cast. > Anybody has an objection to turning ISA_DMA_API off ? Then you can remove all of the DMA api stuff in powerpc's asm/dma.h but some of it looks like it might be in use. -- To unsubscribe from this list: send the line "unsubscribe linux-next" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
