From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 38E81C37121 for ; Mon, 21 Jan 2019 19:44:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0A5C320844 for ; Mon, 21 Jan 2019 19:44:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="key not found in DNS" (0-bit key) header.d=codeaurora.org header.i=@codeaurora.org header.b="UytXDuTU"; dkim=fail reason="key not found in DNS" (0-bit key) header.d=codeaurora.org header.i=@codeaurora.org header.b="J1w8jovS" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728109AbfAUToO (ORCPT ); Mon, 21 Jan 2019 14:44:14 -0500 Received: from smtp.codeaurora.org ([198.145.29.96]:41386 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727764AbfAUToN (ORCPT ); Mon, 21 Jan 2019 14:44:13 -0500 Received: by smtp.codeaurora.org (Postfix, from userid 1000) id 8021360866; Mon, 21 Jan 2019 19:44:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=codeaurora.org; s=default; t=1548099852; bh=rF77RCWbWZur6KREszBmKEh8qdl8SemN/uWDuL0OL8g=; h=Date:From:To:cc:Subject:In-Reply-To:References:From; b=UytXDuTUdIWUb2NC9eY2xUl70tZdhpLERCvqYoyusyqTJWnuvpddpDCY8cnSnUOD0 7BVViJz6OoPp9Whs3dXS/dut9XUTAjzwRgfhAWTg8ys3/zwE8GhGg8F2suEFZmbDDR BD5bNyw3lw7LowC6RO+hT1Ml/mkiy6rkOhUkVpQE= Received: from lmark-linux.qualcomm.com (i-global254.qualcomm.com [199.106.103.254]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) (Authenticated sender: lmark@smtp.codeaurora.org) by smtp.codeaurora.org (Postfix) with ESMTPSA id 0C6D860112; Mon, 21 Jan 2019 19:44:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=codeaurora.org; s=default; t=1548099851; bh=rF77RCWbWZur6KREszBmKEh8qdl8SemN/uWDuL0OL8g=; h=Date:From:To:cc:Subject:In-Reply-To:References:From; b=J1w8jovSt47kiS/w56M+ZilqkOBzhGLxXbFMY/iIaA4BnIg7tfJb2J3ib1I708UYV o41mHdC/4+1Zxggsxz87EsIbxkn/5Zhca+GC8SWKUwuNQIYkkqa8gL0zKa/fs52880 dZRg65ba+kJJP3bppUfzDG7XNjo7AFDnZq17LRVI= DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 0C6D860112 Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=lmark@codeaurora.org Date: Mon, 21 Jan 2019 11:44:10 -0800 (PST) From: Liam Mark X-X-Sender: lmark@lmark-linux.qualcomm.com To: Christoph Hellwig cc: Laura Abbott , sumit.semwal@linaro.org, arve@android.com, tkjos@android.com, maco@android.com, joel@joelfernandes.org, christian@brauner.io, devel@driverdev.osuosl.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org, afd@ti.com, john.stultz@linaro.org Subject: Re: [PATCH 3/4] dma-buf: add support for mapping with dma mapping attributes In-Reply-To: <20190121083046.GD12420@infradead.org> Message-ID: References: <1547836667-13695-1-git-send-email-lmark@codeaurora.org> <1547836667-13695-4-git-send-email-lmark@codeaurora.org> <20190119102527.GA17723@infradead.org> <7ae73c39-9049-bcf6-775f-b0817ba0ec5f@redhat.com> <20190121083046.GD12420@infradead.org> User-Agent: Alpine 2.10 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 21 Jan 2019, Christoph Hellwig wrote: > On Sat, Jan 19, 2019 at 08:50:41AM -0800, Laura Abbott wrote: > > > And who is going to decide which ones to pass? And who documents > > > which ones are safe? > > > > > > I'd much rather have explicit, well documented dma-buf flags that > > > might get translated to the DMA API flags, which are not error checked, > > > not very well documented and way to easy to get wrong. > > > > > > > I'm not sure having flags in dma-buf really solves anything > > given drivers can use the attributes directly with dma_map > > anyway, which is what we're looking to do. The intention > > is for the driver creating the dma_buf attachment to have > > the knowledge of which flags to use. > > Well, there are very few flags that you can simply use for all calls of > dma_map*. And given how badly these flags are defined I just don't want > people to add more places where they indirectly use these flags, as > it will be more than enough work to clean up the current mess. > > What flag(s) do you want to pass this way, btw? Maybe that is where > the problem is. > The main use case is for allowing clients to pass in DMA_ATTR_SKIP_CPU_SYNC in order to skip the default cache maintenance which happens in dma_buf_map_attachment and dma_buf_unmap_attachment. In ION the buffers aren't usually accessed from the CPU so this allows clients to often avoid doing unnecessary cache maintenance. Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project