From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with ESMTP id 178BC6B02A8 for ; Tue, 13 Jul 2010 04:31:29 -0400 (EDT) Date: Tue, 13 Jul 2010 17:30:43 +0900 Subject: Re: [RFC 3/3] mm: iommu: The Virtual Contiguous Memory Manager From: FUJITA Tomonori In-Reply-To: <20100713092012.7c1fe53e@lxorguk.ukuu.org.uk> References: <4C3BFDD3.8040209@codeaurora.org> <20100713145852C.fujita.tomonori@lab.ntt.co.jp> <20100713092012.7c1fe53e@lxorguk.ukuu.org.uk> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-Id: <20100713173028M.fujita.tomonori@lab.ntt.co.jp> Sender: owner-linux-mm@kvack.org To: alan@lxorguk.ukuu.org.uk Cc: fujita.tomonori@lab.ntt.co.jp, 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 List-ID: 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 think that the current DMA API with the above helper functions should work well drivers that want virtually linear large memory areas (such as xfs). -- 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/ . Don't email: email@kvack.org