From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759532AbXLRQvZ (ORCPT ); Tue, 18 Dec 2007 11:51:25 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756948AbXLRQvS (ORCPT ); Tue, 18 Dec 2007 11:51:18 -0500 Received: from hp3.statik.tu-cottbus.de ([141.43.120.68]:45603 "EHLO hp3.statik.tu-cottbus.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756150AbXLRQvR (ORCPT ); Tue, 18 Dec 2007 11:51:17 -0500 Message-ID: <4767FA62.9060002@s5r6.in-berlin.de> Date: Tue, 18 Dec 2007 17:50:42 +0100 From: Stefan Richter User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.8.1.11) Gecko/20071128 SeaMonkey/1.1.7 MIME-Version: 1.0 To: akepner@sgi.com CC: Andrew Morton , grundler@parisc-linux.org, jbarnes@virtuousgeek.org, jes@sgi.com, randy.dunlap@oracle.com, rdreier@cisco.com, James.Bottomley@steeleye.com, davem@davemloft.net, linux-kernel@vger.kernel.org Subject: Re: [RFC] dma: passing "attributes" to dma_map_* routines References: <20071218001758.GO21916@sgi.com> In-Reply-To: <20071218001758.GO21916@sgi.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org akepner@sgi.com wrote: > Waaay back in October I sent some patches for passing additional > attributes to the dma_map_* routines: > > http://marc.info/?l=linux-kernel&m=119137949604365&w=2 Do I understand correctly?: A device and the CPUs communicate via two separate memory areas: A data buffer and a status FIFO. The NUMA interconnect may reorder accesses of the device to the areas. (Write accesses? Read accesses? Both?) To ensure synchronization between device and CPUs, you want to mark a memory area which is to be dma-mapped with a flag which says: "Writes to the memory region will cause in-flight DMA to be flushed". Whose writes? A write access from the device or a write access from a CPU? -- Stefan Richter -=====-=-=== ==-- =--=- http://arcgraph.de/sr/