Re: [PATCH v3] V4L: add two new ioctl()s for multi-size videobuffer management

From: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
To: Hans Verkuil <hverkuil@xs4all.nl>
Cc: Sakari Ailus <sakari.ailus@iki.fi>,
	Linux Media Mailing List <linux-media@vger.kernel.org>,
	Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	Mauro Carvalho Chehab <mchehab@infradead.org>,
	Pawel Osciak <pawel@osciak.com>
Subject: Re: [PATCH v3] V4L: add two new ioctl()s for multi-size videobuffer management
Date: Thu, 28 Jul 2011 12:26:51 +0200 (CEST)	[thread overview]
Message-ID: <Pine.LNX.4.64.1107281152010.20737@axis700.grange> (raw)
In-Reply-To: <201107261305.29863.hverkuil@xs4all.nl>

On Tue, 26 Jul 2011, Hans Verkuil wrote:

[snip]

> I am happy with the API. The only thing that's unclear to me is whether you can call
> CREATE_BUFS after REQBUFS. And if not, then why not? It would also be helpful to see
> the full patch series as the last one was from April. It is interesting to see how
> this will interface with vb2.

I think it would be logical to allow both, since we anyway need 
REQBUFS(count=0) for freeing of buffers. This would confirm, that buffers 
vreated with either of these methods are indistinguishable. Then we shall 
define:

CREATE_BUFS after REQBUFS or after earlier CREATE_BUFS adds more buffers
REQBUFS(count=0) frees all buffers
REQBUFS(count > 0) frees all buffers and allocates new ones

Yes, I'll extend the documentation with this.

Thanks
Guennadi
---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
http://www.open-technology.de/