linux-kernel - Re: DMA from memory to local bus

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Date:	Fri, 28 Nov 2008 21:24:40 -0600
From:	Robert Hancock <hancockr@...w.ca>
To:	linux-kernel@...r.kernel.org
Cc:	maciej.sosnowski@...el.com, dan.j.williams@...el.com
Subject:  Re: DMA from memory to local bus

Hommel, Thomas (GE EntSol, Intelligent Platforms) wrote:
> Hi all,
> I'm currently developing a driver and want to make use of the DMA
> offload engine. Data has to be transferred from memory to a device on
> the local bus and vice versa.
> At a first look, the function dma_async_memcpy_buf_to_buf() seemed to be
> suitable, but it does not translate addresses correctly. Both addresses
> are treated as if they were in memory.

That would be the normal use of these things, I believe.. normally when 
copying to/from a device the device does it itself with bus master DMA.

> In my configuration, the buffer is located in memory, but the device's
> I/O space is mapped into vmalloc space via ioremap(). How can I access
> the I/O space corectly from the DMA controller?
> 
> Thanks for your help
> Thomas

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