Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757516Ab0GNTeI (ORCPT ); Wed, 14 Jul 2010 15:34:08 -0400 Received: from 8bytes.org ([88.198.83.132]:36383 "EHLO 8bytes.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753893Ab0GNTeG (ORCPT ); Wed, 14 Jul 2010 15:34:06 -0400 Date: Wed, 14 Jul 2010 21:34:03 +0200 From: Joerg Roedel To: Zach Pfeffer Cc: Hari Kanigeri , Daniel Walker , Andi Kleen , Randy Dunlap , mel@csn.ul.ie, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [RFC 3/3] mm: iommu: The Virtual Contiguous Memory Manager Message-ID: <20100714193403.GC23755@8bytes.org> References: <1277877350-2147-1-git-send-email-zpfeffer@codeaurora.org> <1277877350-2147-3-git-send-email-zpfeffer@codeaurora.org> <20100701101746.3810cc3b.randy.dunlap@oracle.com> <20100701180241.GA3594@basil.fritz.box> <4C2D908E.9030309@codeaurora.org> <20100710143635.GA10080@8bytes.org> <4C3BF7C1.9040904@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4C3BF7C1.9040904@codeaurora.org> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1144 Lines: 25 On Mon, Jul 12, 2010 at 10:21:05PM -0700, Zach Pfeffer wrote: > Joerg Roedel wrote: > > The DMA-API already does this with the help of IOMMUs if they are > > present. What is the benefit of your approach over that? > > The grist to the DMA-API mill is the opaque scatterlist. Each > scatterlist element brings together a physical address and a bus > address that may be different. The set of scatterlist elements > constitute both the set of physical buffers and the mappings to those > buffers. My approach separates these two things into a struct physmem > which contains the set of physical buffers and a struct reservation > which contains the set of bus addresses (or device addresses). Each > element in the struct physmem may be of various lengths (without > resorting to chaining). A map call maps the one set to the other. Okay, thats a different concept, where is the benefit? Joerg -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/