From mboxrd@z Thu Jan 1 00:00:00 1970 From: "hch@lst.de" Subject: Re: [PATCH] lib/scatterlist: Provide a DMA page iterator Date: Wed, 16 Jan 2019 17:06:39 +0100 Message-ID: <20190116160639.GA28619@lst.de> References: <20190114094856.GB29604@lst.de> <1fb20ab4b171b281e9994b6c55734c120958530b.camel@vmware.com> <2b440a3b-ed2f-8fd6-a21e-97ca0b2f5db9@gmail.com> <20190115152029.GB2325@lst.de> <41d0616e95fb48942404fb54d82249f5700affb1.camel@vmware.com> <20190115183133.GA12350@lst.de> <20190115205801.GA15432@lst.de> <01e5522bf88549bfdaea1430fece23cb3d1a1a55.camel@vmware.com> <8aadac80-da9b-b52a-a4bf-066406127117@amd.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <8aadac80-da9b-b52a-a4bf-066406127117@amd.com> Sender: linux-kernel-owner@vger.kernel.org To: "Koenig, Christian" Cc: Thomas Hellstrom , "hch@lst.de" , "linux-kernel@vger.kernel.org" , "yong.zhi@intel.com" , "daniel.vetter@ffwll.ch" , "linux-rdma@vger.kernel.org" , "linux-media@vger.kernel.org" , "bingbu.cao@intel.com" , "jian.xu.zheng@intel.com" , "tian.shu.qiu@intel.com" , "shiraz.saleem@intel.com" , "sakari.ailus@linux.intel.com" , "dri-devel@lists.freedesktop.org" , "jgg@ziepe.ca" List-Id: linux-rdma@vger.kernel.org On Wed, Jan 16, 2019 at 07:28:13AM +0000, Koenig, Christian wrote: > To summarize once more: We have an array of struct pages and want to > coherently map that to a device. And the answer to that is very simple: you can't. What is so hard to understand about? If you want to map arbitrary memory it simply can't be done in a coherent way on about half of our platforms. > If that is not possible because of whatever reason we want to get an > error code or even not load the driver from the beginning. That is a bullshit attitude. Just like everyone else makes their drivers work you should not be lazy. > > bool dma_streaming_is_coherent(const struct device *) > > > > API to help us decide when to load or not. > > Yes, please. Hell no.