From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sat, 14 Dec 2002 15:22:05 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sat, 14 Dec 2002 15:22:04 -0500 Received: from spiderman.spectsoft.com ([216.126.222.67]:46596 "EHLO trashbin1.spectsoft.com") by vger.kernel.org with ESMTP id ; Sat, 14 Dec 2002 15:22:02 -0500 Subject: Re: DMA from SCSI controller to PCI frame buffer memory. From: Jason Howard To: linux-kernel@vger.kernel.org In-Reply-To: <1039837312.25121.115.camel@irongate.swansea.linux.org.uk> References: <1039806910.21196.29.camel@bmagic.spectsoft.com> <1039837312.25121.115.camel@irongate.swansea.linux.org.uk> Content-Type: text/plain Organization: SpectSoft, LLC Message-Id: <1039897793.21189.53.camel@bmagic.spectsoft.com> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.2.0 Date: 14 Dec 2002 12:29:54 -0800 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > In theory you can mmap the frame buffer memory, then do O_DIRECT I/O > into it. In practice it will buffer (I hope it still does). One of the > problems is that there are huge lists of PCI->AGP DMA errata in > chipsets. I am not accessing the AGP bus as my frame buffer is located on the PCI bus. 00:08.0 Multimedia video controller: Unknown device f1d0:efac Subsystem: Unknown device f1d0:efac Flags: bus master, stepping, medium devsel, latency 64, IRQ 10 Memory at f4000000 (32-bit, non-prefetchable) [size=4K] Memory at f6000000 (32-bit, prefetchable) [size=16M] (I am working with the second memory address) Any recommendations on where to start hacking? Would it be a good idea to add O_DIRECT to a mmaped PCI space? The kernel should not be doing any buffering whatsoever, as we will be coming close to filling the pci bus up with transfers from direct disk->fb already. (We are already doing buffering on the FB card as well) Jason -- Jason Howard Professional: SpectSoft, LLC http://www.spectsoft.com jason@spectsoft.com Phone: +1.209.847.7812 Fax: +1.209.847.7859 Personal: http://www.psinux.org jason@psinux.org Cell: +1.209.968.1289 Text Message: jasonsphone@psinux.org