From owner-freebsd-hackers@FreeBSD.ORG Wed Oct 26 16:12:40 2005 Return-Path: X-Original-To: freebsd-hackers@freebsd.org Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 7AADD16A41F for ; Wed, 26 Oct 2005 16:12:40 +0000 (GMT) (envelope-from dinesh@alphaque.com) Received: from ns2.alphaque.com (ns2.alphaque.com [202.75.47.153]) by mx1.FreeBSD.org (Postfix) with SMTP id D900643D46 for ; Wed, 26 Oct 2005 16:12:38 +0000 (GMT) (envelope-from dinesh@alphaque.com) Received: (qmail 78737 invoked by uid 0); 26 Oct 2005 16:12:35 -0000 Received: from lucifer.net-gw.com (HELO prophet.alphaque.com) (202.75.47.153) by lucifer.net-gw.com with SMTP; 26 Oct 2005 16:12:35 -0000 Received: from [127.0.0.1] (localhost [127.0.0.1]) by prophet.alphaque.com (8.13.4/8.13.4) with ESMTP id j9QG6mvD000833; Thu, 27 Oct 2005 00:06:49 +0800 (MYT) (envelope-from dinesh@alphaque.com) Message-ID: <435FA998.2050409@alphaque.com> Date: Thu, 27 Oct 2005 00:06:48 +0800 From: Dinesh Nair User-Agent: Mozilla/5.0 (X11; U; FreeBSD i386; en-US; rv:1.8b) Gecko/20050915 MIME-Version: 1.0 To: Scott Long References: <435EEC56.9080708@samsco.org> <435F428E.50609@alphaque.com> <200510261130.45506.jhb@freebsd.org> <435FA6A9.4000600@samsco.org> In-Reply-To: <435FA6A9.4000600@samsco.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: freebsd-hackers@freebsd.org Subject: Re: [Fwd: Re: use of bus_dmamap_sync] X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 26 Oct 2005 16:12:40 -0000 On 10/26/05 23:54 Scott Long said the following: > The value of the map is an implementation detail, which is why it's an > opaque typedef. Portable code should always assume that the map has > valid data. Now, specifically for i386, if you have a device with a right, so for portability's sake, bus_dmamap_sync should be used anyway. > twe), and you are not using PAE, then yes the map will be NULL and the > syncs will do nothing. Assuming that all three of these cases are false > is not good, though. well, they are in my situation, so obviously bus dma is not the cause of the problem i'm seeing. thanx to both scottl and jhb for the explanation. this throws a lot of light onto the handling of dma access to devices for me. -- Regards, /\_/\ "All dogs go to heaven." dinesh@alphaque.com (0 0) http://www.alphaque.com/ +==========================----oOO--(_)--OOo----==========================+ | for a in past present future; do | | for b in clients employers associates relatives neighbours pets; do | | echo "The opinions here in no way reflect the opinions of my $a $b." | | done; done | +=========================================================================+