From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from perceval.ideasonboard.com ([95.142.166.194]:45211 "EHLO perceval.ideasonboard.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751490Ab2GTKOp (ORCPT ); Fri, 20 Jul 2012 06:14:45 -0400 From: Laurent Pinchart To: Guennadi Liakhovetski Cc: Hans Verkuil , linux-media@vger.kernel.org, Tomasz Stanislawski , Pawel Osciak , Hans de Goede , Mauro Carvalho Chehab Subject: Re: [RFCv3 PATCH 00/33] Core and vb2 enhancements Date: Fri, 20 Jul 2012 12:14:50 +0200 Message-ID: <2999684.W2D4Cvl3k2@avalon> In-Reply-To: References: <1340866107-4188-1-git-send-email-hverkuil@xs4all.nl> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-media-owner@vger.kernel.org List-ID: Hi Guennadi, On Friday 20 July 2012 11:55:31 Guennadi Liakhovetski wrote: > On Thu, 28 Jun 2012, Hans Verkuil wrote: > > Hi all, > > > > This is the third version of this patch series. > > > > The first version is here: > > > > http://www.mail-archive.com/linux-media@vger.kernel.org/msg47558.html > > Nice to see an owner concept added to the vb2. In soc-camera we're also > using a concept of a "streamer" user. This is the user, that first calls > one of data-flow related ioctl()s, like s_fmt(), streamon(), streamoff() > and all buffer queue-related operations. I realise that this your > patch-set only deals with the buffer queue, but in principle, do you think > it would make sense to use such a concept globally? We probably don't want > to let other processes mess with any of the above calls as long as one > process is actively managing the streaming. I think that's a good idea (the uvcvideo driver implements something similar), but I'm not sure whether the spec currently describes the expected behaviour and relationships between ioctls correctly. That could be a topic for the V4L2 ambiguities discussions during KS. Such a a mechanism should not be imposed on drivers though, as it probably wouldn't cover all use cases (think about mem-to-mem drivers where the format is per file-handle for instance). -- Regards, Laurent Pinchart