From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754409Ab1LIOYL (ORCPT ); Fri, 9 Dec 2011 09:24:11 -0500 Received: from earthlight.etchedpixels.co.uk ([81.2.110.250]:35650 "EHLO pyramind.ukuu.org.uk" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754361Ab1LIOYJ (ORCPT ); Fri, 9 Dec 2011 09:24:09 -0500 Date: Fri, 9 Dec 2011 14:24:05 +0000 From: Alan Cox To: Arnd Bergmann Cc: Daniel Vetter , "Semwal, Sumit" , linux@arm.linux.org.uk, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, linux-mm@kvack.org, linux-media@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [Linaro-mm-sig] [RFC v2 1/2] dma-buf: Introduce dma buffer sharing mechanism Message-ID: <20111209142405.6f371be6@pyramind.ukuu.org.uk> In-Reply-To: <201112091413.03736.arnd@arndb.de> References: <1322816252-19955-1-git-send-email-sumit.semwal@ti.com> <201112071340.35267.arnd@arndb.de> <201112091413.03736.arnd@arndb.de> X-Mailer: Claws Mail 3.7.10 (GTK+ 2.24.8; 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 > I still don't think that's possible. Please explain how you expect > to change the semantics of the streaming mapping API to allow multiple > mappers without having explicit serialization points that are visible > to all users. For simplicity, let's assume a cache coherent system I would agree. It's not just about barriers but in many cases where you have multiple mappings by hardware devices the actual hardware interface is specific to the devices. Just take a look at the fencing in TTM and the graphics drivers. Its not something the low level API can deal with, it requires high level knowledge. Alan