From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail202.messagelabs.com (mail202.messagelabs.com [216.82.254.227]) by kanga.kvack.org (Postfix) with SMTP id 30BD66B02A3 for ; Wed, 14 Jul 2010 15:34:03 -0400 (EDT) Date: Wed, 14 Jul 2010 21:34:03 +0200 From: Joerg Roedel 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> Sender: owner-linux-mm@kvack.org 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 List-ID: 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org