From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from smtp.nokia.com ([147.243.1.48]:42924 "EHLO mgw-sa02.nokia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751922Ab1ERTnh (ORCPT ); Wed, 18 May 2011 15:43:37 -0400 Message-ID: <4DD42218.7000302@maxwell.research.nokia.com> Date: Wed, 18 May 2011 22:46:32 +0300 From: Sakari Ailus MIME-Version: 1.0 To: Hans Verkuil CC: Mauro Carvalho Chehab , dri-devel@lists.freedesktop.org, linux-media@vger.kernel.org, Jesse Barker Subject: Re: Summary of the V4L2 discussions during LDS - was: Re: Embedded Linux memory management interest group list References: <201105141302.55100.hverkuil@xs4all.nl> <4DCE6B7B.1080907@redhat.com> <201105152310.31678.hverkuil@xs4all.nl> In-Reply-To: <201105152310.31678.hverkuil@xs4all.nl> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit List-ID: Sender: Hans Verkuil wrote: > Note that many video receivers cannot stall. You can't tell them to wait until > the last buffer finished processing. This is different from some/most? sensors. Not even image sensors. They just output the frame data; if the receiver runs out of buffers the data is just lost. And if any part of the frame is lost, there's no use for other parts of it either. But that's something the receiver must handle, i.e. discard the data and increment frame number (field_count in v4l2_buffer). The interfaces used by image sensors, be they parallel or serial, do not provide means to inform the sensor that the receiver has run out of buffer space. These interfaces are just unidirectional. Regards, -- Sakari Ailus sakari.ailus@maxwell.research.nokia.com