From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@infradead.org>
Subject: Re: Question: how to map SCSI data DMA address to virtual address?
Date: Thu, 2 Mar 2006 17:09:15 +0000
Message-ID: <20060302170915.GA31316@infradead.org>
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To: "Ju, Seokmann" <Seokmann.Ju@lsil.com>
Cc: "Ju, Seokmann" <Seokmann.Ju@engenio.com>, linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org
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On Thu, Mar 02, 2006 at 09:53:06AM -0700, Ju, Seokmann wrote:
> Hi,
> 
> In the 'scsi_cmnd' structure, there are two entries holding address
> information for data to be transferred. One is 'request_buffer' and the
> other one is 'buffer'.
> In case of 'use_sg' is non-zero, those entries indicates the address of
> the scatter-gather table.
> 
> Is there way to get virtual address (so that the data could be accessed
> by the driver) of the actual data in the case of 'use_sg' is non-zero?

For each sg list entry do something like:

	buffer = kmap_atomic(sg->page, KM_USER0) + sg->offset;
	<access buffer>
	kunmap_atomic(buffer - sg->offset, KM_USER0);