From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mx1.redhat.com (ext-mx02.extmail.prod.ext.phx2.redhat.com [10.5.110.6]) by int-mx08.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id n9C7XKev021569 for ; Mon, 12 Oct 2009 03:33:20 -0400 Received: from web23105.mail.ird.yahoo.com (web23105.mail.ird.yahoo.com [217.146.189.45]) by mx1.redhat.com (8.13.8/8.13.8) with SMTP id n9C7X2j7009140 for ; Mon, 12 Oct 2009 03:33:03 -0400 Message-ID: <164184.43566.qm@web23105.mail.ird.yahoo.com> Date: Mon, 12 Oct 2009 07:33:02 +0000 (GMT) From: Mattias Persson To: video4linux-list@redhat.com MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Subject: How to store the latest image without modifying videobuf-core.c 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: Hi, I am developing a driver for a camera. As an example I am using the vivi driver (2.6.28) and the first major difference between my ISR and thread_tick() is that my driver will always attempt to store the latest image, even if nobody is waiting for a new image. In my driver, when all queued buffers are used any new images will be stored in the oldest frame which has already been captured (state == VIDEOBUF_DONE) and here is where my problems start. (If this is wrong, what shall I do to always keep the latest captured image?) In the function videobuf_dqbuf in videobuf-core.c, if a new image is returned by stream_next_buffer and the ISR kicks in before videobuf_dqbuf can set buf->state to VIDEOBUF_IDLE, my driver will modify the image presented to userspace and that is not acceptable. The only solution I can find is to use the spinlock in videobuf_queue when the userspace application is requesting a new image (DQBUF/poll) to check for a new image and set some flag indicating that the buffer can't be overwritten by the ISR. However, this approach would require changes to videobuf-core.c and that doesn't seem right. Can someone please give me some guidance on this? Regards, Mattias __________________________________________________________ Ta semester! - sök efter resor hos Kelkoo. Jämför pris på flygbiljetter och hotellrum här: http://www.kelkoo.se/c-169901-resor-biljetter.html?partnerId=96914052 -- video4linux-list mailing list Unsubscribe mailto:video4linux-list-request@redhat.com?subject=unsubscribe https://www.redhat.com/mailman/listinfo/video4linux-list