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Re: [Xen-devel] USB virt status --- Help please!!!

from [Keir Fraser] [Permanent Link][Original]
To: Harry Butterworth <harry@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] USB virt status --- Help please!!!
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Mon, 14 Nov 2005 09:56:54 +0000
Cc: Ian Pratt <m+Ian.Pratt@xxxxxxxxxxxx>, mark.williamson@xxxxxxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxx, sanjay.kushwaha@xxxxxxxxx
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On 13 Nov 2005, at 18:28, Harry Butterworth wrote:


Is this the right approach? Is the check in dma_map_single overzealous?
When running on Xen, just because Linux has allocated adjacent pages from its 'physical' memory map, doesn't mean they really are physically contiguous. For I/O we have to go to extra effort to really allocate truly contiguous multi-page extents.
So your code is correct. If you can preallocate buffers then you could do that with dma_alloc_coherent and that would guarantee contigous buffers.... 

 -- Keir


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