linux-kernel - Re: [Linaro-mm-sig] [RFC v2 1/2] dma-buf: Introduce dma buffer sharing mechanism

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Date:	Tue, 20 Dec 2011 16:29:42 +0200
From:	Anca Emanuel <anca.emanuel@...il.com>
To:	Robert Morell <rmorell@...dia.com>
Cc:	Arnd Bergmann <arnd@...db.de>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	Mauro Carvalho Chehab <mchehab@...hat.com>,
	Sumit Semwal <sumit.semwal@...com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	"linaro-mm-sig@...ts.linaro.org" <linaro-mm-sig@...ts.linaro.org>,
	"jesse.barker@...aro.org" <jesse.barker@...aro.org>,
	"daniel@...ll.ch" <daniel@...ll.ch>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-media@...r.kernel.org" <linux-media@...r.kernel.org>
Subject: Re: [Linaro-mm-sig] [RFC v2 1/2] dma-buf: Introduce dma buffer
 sharing mechanism

On Tue, Dec 20, 2011 at 4:05 AM, Robert Morell <rmorell@...dia.com> wrote:
>
> One of the goals of this project is to unify the fragmented space of the
> ARM SoC memory managers so that each vendor doesn't implement their own,
> and they can all be closer to mainline.

That is a very good objective.

> I fear that restricting the use of this buffer sharing mechanism to GPL
> drivers only will prevent that goal from being achieved, if an SoC
> driver has to interact with modules that use a non-GPL license.

If nobody from nvidia have any experience with this kind of work...
Look at Intel. Why are you afraid of ?

> As a hypothetical example, consider laptops that have multiple GPUs.
> Today, these ship with onboard graphics (integrated to the CPU or
> chipset) along with a discrete GPU, where in many cases only the onboard
> graphics can actually display to the screen.  In order for anything
> rendered by the discrete GPU to be displayed, it has to be copied to
> memory available for the smaller onboard graphics to texture from or
> display directly.  Obviously, that's best done by sharing dma buffers
> rather than bouncing them through the GPU.  It's not much of a stretch
> to imagine that we'll see such systems with a Tegra CPU/GPU plus a
> discrete GPU in the future; in that case, we'd want to be able to share
> memory between the discrete GPU and the Tegra system.  In that scenario,
> if this interface is GPL-only, we'd be unable to adopt the dma_buffer
> sharing mechanism for Tegra.
>
> (This isn't too pie-in-the-sky, either; people are already combining
> Tegra with discrete GPUs:
> http://blogs.nvidia.com/2011/11/world%e2%80%99s-first-arm-based-supercomputer-to-launch-in-barcelona/
> )
>
> Thanks,
> Robert

There are other problems ? Some secret agreements with Microsoft ?

I hope to see something open sourced. You can do it nVidia.
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