From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Bottomley Subject: Re: [PATCH 7/8] common: dma-mapping: change alloc/free_coherent method to more generic alloc/free_attrs Date: Fri, 24 Jun 2011 11:15:47 -0500 Message-ID: <1308932147.5929.0.camel@mulgrave> References: <1308556213-24970-1-git-send-email-m.szyprowski@samsung.com> <1308556213-24970-8-git-send-email-m.szyprowski@samsung.com> <201106241751.35655.arnd@arndb.de> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: Received: from bedivere.hansenpartnership.com ([66.63.167.143]:53814 "EHLO bedivere.hansenpartnership.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759725Ab1FXQQI (ORCPT ); Fri, 24 Jun 2011 12:16:08 -0400 In-Reply-To: <201106241751.35655.arnd@arndb.de> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Arnd Bergmann Cc: Marek Szyprowski , linux-arm-kernel@lists.infradead.org, linaro-mm-sig@lists.linaro.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, Kyungmin Park , Joerg Roedel , Russell King - ARM Linux On Fri, 2011-06-24 at 17:51 +0200, Arnd Bergmann wrote: > On Monday 20 June 2011, Marek Szyprowski wrote: > > Introduce new alloc/free/mmap methods that take attributes argument. > > alloc/free_coherent can be implemented on top of the new alloc/free > > calls with NULL attributes. dma_alloc_non_coherent can be implemented > > using DMA_ATTR_NONCOHERENT attribute, dma_alloc_writecombine can also > > use separate DMA_ATTR_WRITECOMBINE attribute. This way the drivers will > > get more generic, platform independent way of allocating dma memory > > buffers with specific parameters. > > > > One more attribute can be usefull: DMA_ATTR_NOKERNELVADDR. Buffers with > > such attribute will not have valid kernel virtual address. They might be > > usefull for drivers that only exports the DMA buffers to userspace (like > > for example V4L2 or ALSA). > > > > mmap method is introduced to let the drivers create a user space mapping > > for a DMA buffer in generic, architecture independent way. > > > > TODO: update all dma_map_ops clients for all architectures > > > > Signed-off-by: Marek Szyprowski > > Signed-off-by: Kyungmin Park > > Yes, I think that is good, but the change needs to be done atomically > across all architectures. This should be easy enough as I believe > all other architectures that use dma_map_ops don't even require > dma_alloc_noncoherent This statement is definitely not true of parisc, and also, I believe, not true of sh, so that would have to figure in the conversion work too. James > but just define it to dma_alloc_coherent > because they have only coherent memory in regular device drivers. > > On a related note, do you plan to make the CMA work use this > transparently, or do you want to have a DMA_ATTR_LARGE or > DMA_ATTR_CONTIGUOUS for CMA? > > Arnd > -- > To unsubscribe from this list: send the line "unsubscribe linux-arch" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html