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Quoting Ingo Molnar <mingo@elte.hu>: > > * Pavel Roskin <proski@gnu.org> wrote: > >> > btw., what are the technical reasons why ndiswrapper cannot be done >> > in userspace, much like the (wildly successful) FUSE concept? >> >> ndiswrapper contains essentially two drivers in one - PCI and USB. >> The PCI driver uses DMA, which should be a strong argument for keeping >> it in the kernel. > > how exactly does it use DMA - how does it allocate the memory it later > on DMAs into, and how does it typically program that DMA target - is > there any control over that in the NDIS protocol - or will NDIS drivers > just write random addresses to the mmio space and then the hardware does > DMA to/from those addresses? [without the NDIS framework having any > knowledge about the encoding of those bits?] Sorry for delay. I'm really not sure. The maintainer of ndiswrapper is currently offline, and I'm just trying to take care of the basic stuff. All I can say is NdisMAllocateSharedMemory maps to dma_alloc_coherent(), and there are some references to scatter-gather lists. There is a call to dma_map_single(), which is ultimately called by the Tx function net_dev->hard_start_xmit. I understand there is some control from NDIS. At least it can request memory available for DMA. > on modern hardware it might even be possible to jail an ndiswrapper > driver to its own pages via the IOMMU. It's possible that ndiswrapper would support Vista drivers only on x86_64, which should always have IOMMU, if I understand correctly. But it would be nice to have proper support for older XP drivers on x86. -- Regards, Pavel Roskin | |||||||||
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