Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754263Ab1DOUJH (ORCPT ); Fri, 15 Apr 2011 16:09:07 -0400 Received: from terminus.zytor.com ([198.137.202.10]:51794 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751489Ab1DOUJG (ORCPT ); Fri, 15 Apr 2011 16:09:06 -0400 Message-ID: <4DA8A5CE.2010004@zytor.com> Date: Fri, 15 Apr 2011 13:08:46 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.15) Gecko/20110307 Fedora/3.1.9-0.39.b3pre.fc14 Thunderbird/3.1.9 MIME-Version: 1.0 To: Clemens Ladisch CC: David Rientjes , Ingo Molnar , Thomas Gleixner , x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [patch v2] x86: allow ZONE_DMA to be configurable References: <4DA82F33.7080403@ladisch.de> In-Reply-To: <4DA82F33.7080403@ladisch.de> 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 Content-Length: 1575 Lines: 42 On 04/15/2011 04:42 AM, Clemens Ladisch wrote: > David Rientjes wrote: >> ZONE_DMA is unnecessary for a large number of machines that do not >> require addressing in the lower 16MB of memory because they do not use >> ISA devices with 16-bit address registers (plus one page byte register). >> >> This patch allows users to disable ZONE_DMA for x86 if they know they >> will not be using such devices with their kernel. >> ... >> config ZONE_DMA >> - def_bool y >> + bool "DMA memory allocation support" if EXPERT > > Better call it "ISA/LPC DMA memory allocation support". > >> + default y > > Does it make sense to have this without CONFIG_ISA_DMA_API? > >> + help >> + DMA memory allocation support allows old ISA devices with 16-bit >> + address registers to allocate memory within the first 16MB of >> + address space. Disable if no such devices will be used. > > "Old ISA devices" might be misleading because ISA does not imply actual > ISA slots; please mention LPC devices like the floppy controller and the > parallel port in ECP mode. > This isn't really a very good edit, as ZONE_DMA isn't inherently limited to ISA/LPC devices (and LPC devices which do LPC-native bus mastering DMA are not affected.) ZONE_DMA is used even for some PCI devices which have restrictions on the DMA address mask. -hpa -- 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/