linux-kernel - Re: [PATCH 2/4 v4] i.MX31: Image Processing Unit DMA and IRQ drivers

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Date:	Tue, 23 Dec 2008 13:09:10 +0300
From:	Dmitry Krivoschekov <dmitry.krivoschekov@...il.com>
To:	Robert Schwebel <r.schwebel@...gutronix.de>
CC:	Guennadi Liakhovetski <g.liakhovetski@....de>,
	linux-kernel@...r.kernel.org,
	linux-fbdev-devel@...ts.sourceforge.net, adaplas@...il.com,
	linux-arm-kernel@...ts.arm.linux.org.uk,
	Dan Williams <dan.j.williams@...el.com>
Subject: Re: [PATCH 2/4 v4] i.MX31: Image Processing Unit DMA and IRQ	drivers

Robert Schwebel wrote:
> On Mon, Dec 22, 2008 at 07:37:53PM +0100, Sascha Hauer wrote:
>> Another thing is the overlay framebuffer. I think it's mainly useful
>> to display video streams.
>
> Right. The idea is that you can push a video stream into /dev/fb1 (for
> example by using the gstreamer fbdev sink) while displaying widgets from
> a GUI toolkit on /dev/fb0.
>
>> Maybe it's better to implement this as a v4l device as unlike the
>> framebuffer API the v4l API is designed to handle different image
>> buffers.
>
> Huh? v4l is image-frames-to-userspace, not vice versa.
>
...and vice versa too, v4l2 is not about input devices only but it is
also related to output devices, v4l2 spec even has a special chapter
dedicated to overlays [1]. Moreover, you can find such a driver within
Freescale's BSP [2]. Another example is Omap's videoout driver [3].


Dmitry

[1]http://v4l2spec.bytesex.org/spec-single/v4l2.html#OVERLAY
[2]http://opensource.freescale.com/git?p=linux-2.6-mx.git;a=blob;f=drivers/media/video/mxc/output/mxc_v4l2_output.c;h=309700bb9d1f3b3f9dcac8a48a16d0775b8ed93a;hb=refs/heads/bsp-imx31ads-rel5
[3]http://git.omapzoom.org/?p=omapkernel.git;a=blob;f=drivers/media/video/omap/omap24xxvout.c;h=25ac1319bae58751cd1a543aa0f320159e10a475;hb=HEAD

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