Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754213Ab0GMIel (ORCPT ); Tue, 13 Jul 2010 04:34:41 -0400 Received: from earthlight.etchedpixels.co.uk ([81.2.110.250]:37236 "EHLO www.etchedpixels.co.uk" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752714Ab0GMIek (ORCPT ); Tue, 13 Jul 2010 04:34:40 -0400 Date: Tue, 13 Jul 2010 09:42:44 +0100 From: Alan Cox To: FUJITA Tomonori Cc: zpfeffer@codeaurora.org, joro@8bytes.org, dwalker@codeaurora.org, andi@firstfloor.org, randy.dunlap@oracle.com, mel@csn.ul.ie, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [RFC 3/3] mm: iommu: The Virtual Contiguous Memory Manager Message-ID: <20100713094244.7eb84f1b@lxorguk.ukuu.org.uk> In-Reply-To: <20100713173028M.fujita.tomonori@lab.ntt.co.jp> References: <4C3BFDD3.8040209@codeaurora.org> <20100713145852C.fujita.tomonori@lab.ntt.co.jp> <20100713092012.7c1fe53e@lxorguk.ukuu.org.uk> <20100713173028M.fujita.tomonori@lab.ntt.co.jp> X-Mailer: Claws Mail 3.7.6 (GTK+ 2.18.9; x86_64-redhat-linux-gnu) Face: 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 Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1287 Lines: 31 On Tue, 13 Jul 2010 17:30:43 +0900 FUJITA Tomonori wrote: > On Tue, 13 Jul 2010 09:20:12 +0100 > Alan Cox wrote: > > > > Why video4linux can't use the DMA API? Doing DMA with vmalloc'ed > > > buffers is a thing that we should avoid (there are some exceptions > > > like xfs though). > > > > Vmalloc is about the only API for creating virtually linear memory areas. > > The video stuff really needs that to avoid lots of horrible special cases > > when doing buffer processing and the like. > > > > Pretty much each driver using it has a pair of functions 'rvmalloc' and > > 'rvfree' so given a proper "vmalloc_for_dma()" type interface can easily > > be switched > > We already have helper functions for DMA with vmap pages, > flush_kernel_vmap_range and invalidate_kernel_vmap_range. I'm not sure they help at all because the DMA user for these pages isn't the video driver - it's the USB layer, and the USB layer isn't specifically aware it is being passed vmap pages. Alan -- 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/