Stefan Richter wrote:

I didn't read the start of this thread and may misunderstand the issue,
but I comment anyway...:

Documentation/DMA-API.txt says the following about (pci_)dma_sync_single
and friends:  "All the parameters must be the same as those passed into
the single mapping API."
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob;f=Documentation/DMA-API.txt;h=5aceb88b3f8b622c8c23ed288f37f42de705c904;hb=HEAD#l367

So, it might be considered an API bug --- but it is a documented one. :-)

Disregard my comment.  I just noticed that there is more qualified
discussion of this in the thread "[PATCH] sky2: Fix WARNING: at
lib/dma-debug.c:902 check_sync".
-- 
Stefan Richter
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http://arcgraph.de/sr/