From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sakari Ailus Subject: Re: Summary of the V4L2 discussions during LDS - was: Re: Embedded Linux memory management interest group list Date: Wed, 18 May 2011 22:46:32 +0300 Message-ID: <4DD42218.7000302@maxwell.research.nokia.com> References: <201105141302.55100.hverkuil@xs4all.nl> <4DCE6B7B.1080907@redhat.com> <201105152310.31678.hverkuil@xs4all.nl> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <201105152310.31678.hverkuil@xs4all.nl> Sender: linux-media-owner@vger.kernel.org To: Hans Verkuil Cc: Mauro Carvalho Chehab , dri-devel@lists.freedesktop.org, linux-media@vger.kernel.org, Jesse Barker List-Id: dri-devel@lists.freedesktop.org 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