From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Garzik Subject: Re: [PATCH] asm-generic: add a dma-mapping.h file Date: Mon, 18 May 2009 18:54:49 -0400 Message-ID: <4A11E739.6080106@pobox.com> References: <20090513043409.GA13577@cynthia.pants.nu> <200905172138.55145.arnd@arndb.de> <4A106E22.1010705@pobox.com> <200905172245.23774.arnd@arndb.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <200905172245.23774.arnd@arndb.de> Sender: linux-m68k-owner@vger.kernel.org To: Arnd Bergmann Cc: Robert Hancock , Tejun Heo , FUJITA Tomonori , alan@lxorguk.ukuu.org.uk, flar@allandria.com, schmitz@biophys.uni-duesseldorf.de, linux-kernel@vger.kernel.org, linux-ide@vger.kernel.org, takata@linux-m32r.org, geert@linux-m68k.org, linux-m68k@vger.kernel.org, ysato@users.sourceforge.jp List-Id: linux-ide@vger.kernel.org Arnd Bergmann wrote: > h8300 and m32r currently do not provide a DMA mapping API > and therefore cannot use the ATA drivers. This adds a > generic version of dma-mapping.h for architectures that > have none or very minimal actual support for DMA in hardware > and makes the two architectures use it. > > Signed-off-by: Arnd Bergmann > --- > On Sunday 17 May 2009 20:05:54 Jeff Garzik wrote: > >> That's what needs to happen. We provide no-op functions for e.g. PCI >> and x86 DMI, for platforms where this support does not exist. >> >> Pretty much all architectures support some form of ATA. m68k, m32r, >> h8300 and microblaze all have IDE interface, which means that libata >> needs to work on that platform. >> >> The only !ATA arch in the entire kernel is s390, AFAICT. > > m68k only defines NO_DMA for Sun3 and Dragonball. Sun3 does > not have ATA, Dragonball could probably just enable HAS_DMA. > > --- > arch/h8300/Kconfig | 2 +- > arch/h8300/include/asm/dma-mapping.h | 1 + > arch/m32r/Kconfig | 2 +- > arch/m32r/include/asm/dma-mapping.h | 1 + > include/asm-generic/dma-mapping.h | 399 ++++++++++++++++++++++++++++++++++ > 5 files changed, 403 insertions(+), 2 deletions(-) > create mode 100644 arch/h8300/include/asm/dma-mapping.h > create mode 100644 arch/m32r/include/asm/dma-mapping.h > create mode 100644 include/asm-generic/dma-mapping.h My main comment is a bit non-specific... I tend to think that all no-dma platforms should provide an API whose implementation always returns errors, e.g. an inlined version of dma-mapping-broken.h. That sort of setup permits the compiler's dead code elimination to work on these no-dma platforms, while not crapping up the libata code with a bunch of ifdefs. Jeff