From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCH] ata: libata depends on HAS_DMA Date: Fri, 15 May 2009 20:21:53 +0900 Message-ID: <4A0D5051.90708@gmail.com> References: <20090513043409.GA13577@cynthia.pants.nu> <20090514091928R.fujita.tomonori@lab.ntt.co.jp> <4A0CFE1F.5080409@gmail.com> <200905151316.31521.arnd@arndb.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from wf-out-1314.google.com ([209.85.200.172]:30041 "EHLO wf-out-1314.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751262AbZEOLV4 (ORCPT ); Fri, 15 May 2009 07:21:56 -0400 In-Reply-To: <200905151316.31521.arnd@arndb.de> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Arnd Bergmann Cc: FUJITA Tomonori , hancockrwd@gmail.com, alan@lxorguk.ukuu.org.uk, flar@allandria.com, schmitz@biophys.uni-duesseldorf.de, linux-kernel@vger.kernel.org, jgarzik@pobox.com, linux-ide@vger.kernel.org, takata@linux-m32r.org, geert@linux-m68k.org, linux-m68k@vger.kernel.org, ysato@users.sourceforge.jp Hello, Arnd Bergmann wrote: > On Friday 15 May 2009, Tejun Heo wrote: >> FUJITA Tomonori wrote: >>> Can libata call dma_supported() per device to decide DMA or PIO mode? >>> Then, we can solve this problem by add dummy DMA API (just calls BUG) >>> on such architectures, without Kconfig magic or adding ifdef (like the >>> old ide stack does), I think. > > That would be the !CONFIG_PCI half of the old > include/asm-generic/dma-mapping.h file that you just removed, > right? > > In general, I'd prefer keeping the asm-generic/dma-mapping-broken.h > implementation that gives us a compile-time error, but maybe there > is an even better option based on the mn10300 implementation which > basically pretends everything works with just page_to_phys() mappings. Don't know much history here but I don't wanna sprinkle ifdefs around in libata so I would much prefer dummy implementation which doesn't fail compile. >> Sure it can. Which specific drivers are we talking about? > > The main problem is libata-core.c, which references DMA mapping > API calls that are only implemented on architectures setting > CONFIG_HAS_DMA. Yeah, sure, libata-core is used by every driver but I was wondering whether only SFF drivers are of interest or there are others. Thanks. -- tejun