Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964813AbWEBNfO (ORCPT ); Tue, 2 May 2006 09:35:14 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964814AbWEBNfO (ORCPT ); Tue, 2 May 2006 09:35:14 -0400 Received: from pentafluge.infradead.org ([213.146.154.40]:22763 "EHLO pentafluge.infradead.org") by vger.kernel.org with ESMTP id S964813AbWEBNfM (ORCPT ); Tue, 2 May 2006 09:35:12 -0400 Date: Tue, 2 May 2006 14:35:07 +0100 From: Christoph Hellwig To: Roland Dreier Cc: Arjan van de Ven , "Bryan O'Sullivan" , openib-general@openib.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 5 of 13] ipath - use proper address translation routine Message-ID: <20060502133507.GA26704@infradead.org> Mail-Followup-To: Christoph Hellwig , Roland Dreier , Arjan van de Ven , Bryan O'Sullivan , openib-general@openib.org, linux-kernel@vger.kernel.org References: <1ab168913f0fea5d18b4.1145913781@eng-12.pathscale.com> <1146509646.20760.63.camel@laptopd505.fenrus.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.1i 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 Content-Length: 1224 Lines: 26 On Mon, May 01, 2006 at 12:00:00PM -0700, Roland Dreier wrote: > Arjan> do you really NEED the vaddr? (most of the time linux > Arjan> drivers don't need it, while other OSes do) If you really > Arjan> need it you should grab it at dma_map time ... (and > Arjan> realize that it's not kernel addressable per se ;) > > Yes, they need some kind of vaddr. > > It's kind of a layering problem. The IB stack assumes that IB devices > have a DMA engine that deals with bus addresses. But the ipath driver > has to simulate this by using a memcpy on the CPU to move data to the > PCI device. > > I really don't know what the right solution is. Maybe having some way > to override the dma mapping operations so that the ipath driver can > keep the info it needs? Or stop doing the dma mapping in the IB upper level drivers. I told you that we'll get broken hardware that doesn't want dma mapping in the upper level driver, and pathscale created exactly that :) - 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/