From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mx3.redhat.com (mx3.redhat.com [172.16.48.32]) by int-mx1.corp.redhat.com (8.13.1/8.13.1) with ESMTP id mA9H1pmh028855 for ; Sun, 9 Nov 2008 12:01:51 -0500 Received: from smtp8-g19.free.fr (smtp8-g19.free.fr [212.27.42.65]) by mx3.redhat.com (8.13.8/8.13.8) with ESMTP id mA9H1cPd031903 for ; Sun, 9 Nov 2008 12:01:38 -0500 Received: from smtp8-g19.free.fr (localhost [127.0.0.1]) by smtp8-g19.free.fr (Postfix) with ESMTP id 5BCA432A7D2 for ; Sun, 9 Nov 2008 18:01:38 +0100 (CET) Received: from velvet (mur31-2-82-243-122-54.fbx.proxad.net [82.243.122.54]) by smtp8-g19.free.fr (Postfix) with ESMTP id 0D00432A7C4 for ; Sun, 9 Nov 2008 18:01:37 +0100 (CET) To: video4linux-list@redhat.com From: Robert Jarzmik Date: Sun, 09 Nov 2008 18:01:37 +0100 Message-ID: <87prl4x28e.fsf@free.fr> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Subject: pxa_camera: DMA alignment requirement List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: video4linux-list-bounces@redhat.com Errors-To: video4linux-list-bounces@redhat.com List-ID: Hello, In the pxa camera driver, the 3 DMA channels used are MMU page aligned. Does somebody remember where that constraint comes from ? I'm wondering because the planar YUV format generated is something like this for a 640 * 480 image : - Y plane => 640 * 480 bytes = 307200 (and this happens to be a multiple of pagesize : 307200 = 4096 * 75) - U plane => 640 * 480 / 2 bytes = 153600 (and this is not a multiple of 4096) - padding to reach next page : 2048 bytes - V plane => 153600 bytes - padding to reach next page : 2048 bytes This means a user space library should be kernel pagesize aware to transform the output image. I don't really understand the necessity of page aligned DMA channels. Would someone tell me please ? -- Robert -- video4linux-list mailing list Unsubscribe mailto:video4linux-list-request@redhat.com?subject=unsubscribe https://www.redhat.com/mailman/listinfo/video4linux-list