Messages in this thread |  | | Date | Fri, 13 Sep 2002 12:36:41 -0700 (PDT) | Subject | Re: Streaming DMA mapping question | From | "David S. Miller" <> |
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From: Adam Kropelin <akropel1@rochester.rr.com> Date: Fri, 13 Sep 2002 15:39:16 -0400
According to the docs, you should either unmap or sync your DMA buffer before touching it from the host. The i386 implementation of pci_unmap is empty --no problem; there must not be any unmap work to do on this arch. But the implementation of pci_dma_sync does contain a flush_write_buffers() call. This makes me think that perhaps if I'm going to modify the buffer before I submit it back to the controller I need to do:
Actually, rather it appears that the i386 pci_unmap_*() routines need the write buffer flush as well.
The x86 implementation is a bad example to read if you're trying to see what the worst case scenerio is.
Just follow the document and your driver will work properly on all platforms. DMA-mapping.txt was meant to be written in a way such that you should not ever need to look at an implementation of the interfaces to figure out how to use them. - 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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