linux-kernel - Re: [HOWTO] accessing the DMA mapped data

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Message-ID: <464304DD.9070600@cdac.in>
Date:	Thu, 10 May 2007 17:11:17 +0530
From:	Mahesh <maheshk@...c.in>
To:	David Miller <davem@...emloft.net>
CC:	linux-kernel@...r.kernel.org, kernelnewbies@...linux.org
Subject: Re: [HOWTO] accessing the DMA mapped data

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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