Message-ID: <464304DD.9070600@cdac.in>
Date: Thu, 10 May 2007 17:11:17 +0530
From: Mahesh <maheshk@cdac.in>
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To: David Miller <davem@davemloft.net>
CC: linux-kernel@vger.kernel.org, kernelnewbies@nl.linux.org
Subject: Re: [HOWTO] accessing the DMA mapped data
References: <4642D095.6070305@cdac.in><20070510.014751.74749340.davem@daveml
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	<20070510.043233.08323827.davem@davemloft.net>
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Hi,
> You haven't given an example of where this might actually happen.
>
> The driver is where the DMA mappings almost always occur because
> that is the layer that knows the bus technology and therefore
> the correct DMA interfaces to call.
>
> What kind of driver do you have and what is this upper layer
> doing the mappings for you but not giving you a pointer to
> the kernel buffer as well?
>   
Here I am dealing with a infiniband (see www.openfabrics.org) network 
device driver. The layer above the
driver is the standard infiniband core interface. Now I have a situation 
where I need to peek into the packets
and do some modifications(some hacking). So I just want know whether I 
can access the original data region
using the bus address generated by the dma_map_single.

FYI, architecture I am working on is x86_64.

-Mahesh


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