From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752012AbWCBQ6U (ORCPT ); Thu, 2 Mar 2006 11:58:20 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752008AbWCBQ6U (ORCPT ); Thu, 2 Mar 2006 11:58:20 -0500 Received: from pentafluge.infradead.org ([213.146.154.40]:11739 "EHLO pentafluge.infradead.org") by vger.kernel.org with ESMTP id S1752011AbWCBQ6T (ORCPT ); Thu, 2 Mar 2006 11:58:19 -0500 Subject: Re: Question: how to map SCSI data DMA address to virtual address? From: Arjan van de Ven To: "Ju, Seokmann" Cc: "Ju, Seokmann" , linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org In-Reply-To: <9738BCBE884FDB42801FAD8A7769C2651420C1@NAMAIL1.ad.lsil.com> References: <9738BCBE884FDB42801FAD8A7769C2651420C1@NAMAIL1.ad.lsil.com> Content-Type: text/plain Date: Thu, 02 Mar 2006 17:58:11 +0100 Message-Id: <1141318691.3206.87.camel@laptopd505.fenrus.org> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 (2.2.3-2.fc4) Content-Transfer-Encoding: 7bit X-SRS-Rewrite: SMTP reverse-path rewritten from by pentafluge.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2006-03-02 at 09:53 -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. use_sg is never non-zero so that's easy > > 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? not really; unless you mapped it. The physical address may already been translated by the iommu... at which point there is no direct mapping to kernel memory. Why do you need to do this? It's generally bad for drivers to snoop data!