From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from co203.xi-lite.net ([149.6.83.203]:37457 "EHLO co203.xi-lite.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750772Ab0AOPCN (ORCPT ); Fri, 15 Jan 2010 10:02:13 -0500 Received: from ONYX.xi-lite.lan (unknown [193.34.35.244]) by co203.xi-lite.net (Postfix) with ESMTP id 8AA0B658345 for ; Fri, 15 Jan 2010 15:02:11 +0000 (GMT) Message-ID: <4B508372.6070608@parrot.com> Date: Fri, 15 Jan 2010 16:02:10 +0100 From: Matthieu CASTET MIME-Version: 1.0 To: v4l2_linux Subject: videobuf cached user mapping Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org List-ID: Hi, Is that possible to have user mapping cached in Memory Mapping mode ? This means buffer allocated by mmap in userspace, will have cache support, and it will be faster to work on it. But how the cache coherency can be done ? For a camera we should : - invalidate cache before dma operation (to have not old buffer data in the cache) - forbid the user to access the buffer during the dma operation (to not pollute the cache) Is it possible ? How can we achieve that ? I see sync method, that seems only called after frame capture ? Or user "User Pointers" is the solution ? But they should have the same problems. Is there some documentation of how "user pointer" are synchronised with dma ? Thanks, Matthieu