From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261268AbVGDIZj (ORCPT ); Mon, 4 Jul 2005 04:25:39 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261287AbVGDIZj (ORCPT ); Mon, 4 Jul 2005 04:25:39 -0400 Received: from [85.8.12.41] ([85.8.12.41]:22716 "EHLO smtp.drzeus.cx") by vger.kernel.org with ESMTP id S261268AbVGDIZ3 (ORCPT ); Mon, 4 Jul 2005 04:25:29 -0400 Message-ID: <42C8F26E.3080403@drzeus.cx> Date: Mon, 04 Jul 2005 10:25:18 +0200 From: Pierre Ossman User-Agent: Mozilla Thunderbird 1.0.2-6 (X11/20050513) X-Accept-Language: en-us, en MIME-Version: 1.0 To: randy_dunlap CC: linux-kernel@vger.kernel.org Subject: Re: [PATCH] ISA DMA API documentation References: <42C712C9.7080603@drzeus.cx> <20050703205834.51b43435.rdunlap@xenotime.net> In-Reply-To: <20050703205834.51b43435.rdunlap@xenotime.net> X-Enigmail-Version: 0.90.1.0 X-Enigmail-Supports: pgp-inline, pgp-mime Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org randy_dunlap wrote: >+The DMA:able address space is the lowest 16 MB of _physical_ memory. > The DMA-able >+Also the transfer block may not cross page boundaries (which are 64k). > I would write: (which are 64 KB). > >if I knew that was correct, but I don't. >Does Linux limit all ISA-DMA to not crossing 64 KB boundaries? >I haven't looked at the code yet, just PC-AT Technical Reference, >which says that DMA controller 1 is limited to 8-bit transfers and >64 KB blocks and DMA controller 2 is limited to 16-bit data transfers >and 128 KB boundaries. >Does i386-compatible and later chipsets or LPC change/affect this? >(I see that you cover 8/16-bit transfers later in the doc.) > > Sorry, my bad. 128k is quite correct for 16-bit data transfers. I've just been using 8-bit transfers so I got a bit too familiar with just those. :) >+To translate the virtual address to a physical use the normal DMA >+API. Do _not_ use isa_virt_to_phys() even though it does the same >+thing. The reason for this is that you will get a requirement to ISA >+(instead of only ISA_DMA_API). > >I don't understand what you are trying to say in: >... is that you will get a requirement to ISA.... >Oh, it's Kconfig-related, right? So maybe: >"... is that you will get a config requirement for ISA..." ? > > > Yes, that's what I'm trying to say. I'll try to make it clearer. Thanks for the feedback. I'll get your suggestions in and post a new patch. Rgds Pierre