From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [RFC 4/4] drm: Add NVIDIA Tegra support Date: Thu, 12 Apr 2012 11:18:19 +0000 Message-ID: <201204121118.19685.arnd@arndb.de> References: <1334146230-1795-1-git-send-email-thierry.reding@avionic-design.de> <20120412071816.GA18252@avionic-0098.mockup.avionic-design.de> <025f01cd1887$da56b6e0$8f0424a0$%szyprowski@samsung.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <025f01cd1887$da56b6e0$8f0424a0$%szyprowski-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org> Sender: linux-tegra-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Marek Szyprowski Cc: 'Thierry Reding' , devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org, 'Daniel Vetter' , 'Joerg Roedel' , dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org, 'Jon Mayo' , iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, 'Colin Cross' , linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, 'Hiroshi Doyu' , Tomasz Stanislawski List-Id: linux-tegra@vger.kernel.org On Thursday 12 April 2012, Marek Szyprowski wrote: > Scatter lists were initially designed for the disk based block io operations, > hence the presence of the in-page offsets and lengths for each chunk. For > multimedia use cases providing an array of struct pages and asking dma-mapping > to map them into contiguous memory is probably all we need. I wonder if > introducing such new calls is a good idea. Anrd, what do think? It will > definitely simplify the drivers and improve the code understanding. On the > other hand it requires a significant amount of work in the dma-mapping > framework for all architectures, but that's not a big issue for me. My feeling is that it's too much like the existing _sg version, so I wouldn't add yet another variant. While having a simple page array is definitely simpler and potentially faster, I think the API is already too complex and we need to be very careful with new additions. Arnd