From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from co203.xi-lite.net ([149.6.83.203]:45696 "EHLO co203.xi-lite.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755314AbZHGImH (ORCPT ); Fri, 7 Aug 2009 04:42:07 -0400 Message-ID: <4A7BE1E7.60203@parrot.com> Date: Fri, 7 Aug 2009 10:12:23 +0200 From: Matthieu CASTET MIME-Version: 1.0 To: Laurent Pinchart CC: David Xiao , Ben Dooks , Hugh Dickins , Robin Holt , "linux-kernel@vger.kernel.org" , v4l2_linux , "linux-arm-kernel@lists.arm.linux.org.uk" Subject: Re: How to efficiently handle DMA and cache on ARMv7 ? (was "Is get_user_pages() enough to prevent pages from being swapped out ?") References: <200908061208.22131.laurent.pinchart@ideasonboard.com> <200908061506.23874.laurent.pinchart@ideasonboard.com> <1249584374.29182.20.camel@david-laptop> <200908070929.53873.laurent.pinchart@ideasonboard.com> In-Reply-To: <200908070929.53873.laurent.pinchart@ideasonboard.com> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 8bit Sender: linux-media-owner@vger.kernel.org List-ID: Laurent Pinchart a écrit : > On Thursday 06 August 2009 20:46:14 David Xiao wrote: > > Think about the simple following use case. An application wants to display > video it acquires from the device to the screen using Xv. The video buffer is > allocated by Xv. Using the v4l2 user pointer streaming method, the device can > DMA directly to the Xv buffer. Using driver-allocated buffers, a memcpy() is > required between the v4l2 buffer and the Xv buffer. > v4l2 got an API (overlay IRRC) that allow drivers to write directly in framebuffer memory. BTW Xv buffer is not always in video memory and the X driver can do a memcpy. Matthieu