From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754253AbbAURbw (ORCPT ); Wed, 21 Jan 2015 12:31:52 -0500 Received: from pandora.arm.linux.org.uk ([78.32.30.218]:44192 "EHLO pandora.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754199AbbAURbk (ORCPT ); Wed, 21 Jan 2015 12:31:40 -0500 Date: Wed, 21 Jan 2015 17:31:28 +0000 From: Russell King - ARM Linux To: Sumit Semwal Cc: linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, t.stanislaws@samsung.com, linaro-kernel@lists.linaro.org, robdclark@gmail.com, daniel@ffwll.ch, m.szyprowski@samsung.com Subject: Re: [RFCv2 2/2] dma-buf: add helpers for sharing attacher constraints with dma-parms Message-ID: <20150121173128.GV26493@n2100.arm.linux.org.uk> References: <1421813807-9178-1-git-send-email-sumit.semwal@linaro.org> <1421813807-9178-3-git-send-email-sumit.semwal@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1421813807-9178-3-git-send-email-sumit.semwal@linaro.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 21, 2015 at 09:46:47AM +0530, Sumit Semwal wrote: > +static int calc_constraints(struct device *dev, > + struct dma_buf_constraints *calc_cons) > +{ > + struct dma_buf_constraints cons = *calc_cons; > + > + cons.dma_mask &= dma_get_mask(dev); I don't think this makes much sense when you consider that the DMA infrastructure supports buses with offsets. The DMA mask is th upper limit of the _bus_ specific address, it is not a mask per-se. What this means is that &= is not the right operation. Moreover, simply comparing masks which could be from devices on unrelated buses doesn't make sense either. However, that said, I don't have an answer for what you want to achieve here. -- FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up according to speedtest.net.