From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx126.postini.com [74.125.245.126]) by kanga.kvack.org (Postfix) with SMTP id E8FCF6B006C for ; Tue, 29 May 2012 11:14:15 -0400 (EDT) Date: Tue, 29 May 2012 11:07:14 -0400 From: Konrad Rzeszutek Wilk Subject: Re: [PATCHv2 3/4] mm: vmalloc: add VM_DMA flag to indicate areas used by dma-mapping framework Message-ID: <20120529150714.GA8293@phenom.dumpdata.com> References: <1337252085-22039-1-git-send-email-m.szyprowski@samsung.com> <1337252085-22039-4-git-send-email-m.szyprowski@samsung.com> <4FBB3B41.8010102@kernel.org> <01e501cd39a8$67f34ea0$37d9ebe0$%szyprowski@samsung.com> <20120524122854.GD11860@linux-sh.org> <001d01cd3caa$a05d0510$e1170f30$%szyprowski@samsung.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <001d01cd3caa$a05d0510$e1170f30$%szyprowski@samsung.com> Sender: owner-linux-mm@kvack.org List-ID: To: Marek Szyprowski Cc: 'KOSAKI Motohiro' , 'Paul Mundt' , 'Minchan Kim' , linux-arm-kernel@lists.infradead.org, linaro-mm-sig@lists.linaro.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, 'Kyungmin Park' , 'Arnd Bergmann' , 'Russell King - ARM Linux' , 'Chunsang Jeong' , 'Krishna Reddy' , 'Hiroshi Doyu' , 'Subash Patel' , 'Nick Piggin' On Mon, May 28, 2012 at 10:19:39AM +0200, Marek Szyprowski wrote: > Hello, > > On Sunday, May 27, 2012 2:35 PM KOSAKI Motohiro wrote: > > > On Thu, May 24, 2012 at 8:28 AM, Paul Mundt wrote: > > > On Thu, May 24, 2012 at 02:26:12PM +0200, Marek Szyprowski wrote: > > >> On Tuesday, May 22, 2012 9:08 AM Minchan Kim wrote: > > >> > Hmm, VM_DMA would become generic flag? > > >> > AFAIU, maybe VM_DMA would be used only on ARM arch. > > >> > > >> Right now yes, it will be used only on ARM architecture, but maybe other architecture will > > >> start using it once it is available. > > >> > > > There's very little about the code in question that is ARM-specific to > > > begin with. I plan to adopt similar changes on SH once the work has > > > settled one way or the other, so we'll probably use the VMA flag there, > > > too. > > > > I don't think VM_DMA is good idea because x86_64 has two dma zones. x86 unaware > > patches make no sense. > > I see no problems to add VM_DMA64 later if x86_64 starts using vmalloc areas for creating > kernel mappings for the dma buffers (I assume that there are 2 dma zones: one 32bit and one > 64bit). Right now x86 and x86_64 don't use vmalloc areas for dma buffers, so I hardly see > how this patch can be considered as 'x86 unaware'. Well they do - kind off. It is usually done by calling vmalloc_32 and then using the DMA API on top of those pages (or sometimes the non-portable virt_to_phys macro). Introducing this and replacing the vmalloc_32 with this seems like a nice step in making those device drivers APIs more portable? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org