linux-kernel - Re: [RFC] dma-buf: Implement test module

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Date:	Thu, 12 Dec 2013 23:30:23 +0100
From:	Daniel Vetter <daniel@...ll.ch>
To:	Thomas Hellstrom <thellstrom@...are.com>
Cc:	Thierry Reding <thierry.reding@...il.com>,
	"linaro-mm-sig@...ts.linaro.org" <linaro-mm-sig@...ts.linaro.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	dri-devel <dri-devel@...ts.freedesktop.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] dma-buf: Implement test module

On Thu, Dec 12, 2013 at 8:34 PM, Thomas Hellstrom <thellstrom@...are.com> wrote:
> On 12/12/2013 03:36 PM, Thierry Reding wrote:
>>
>> This is a simple test module that can be used to allocate, export and
>> delete DMA-BUF objects. It can be used to test DMA-BUF sharing in
>> systems that lack a real second driver.
>>
>>
>
> Looks nice. I wonder whether this could be extended to create a "streaming"
> dma-buf from a user space mapping. That could be used as a generic way to
> implement streaming (user) buffer objects, rather than to add explicit
> support for those in, for example, TTM.

Atm there's no way to get gpus to unbind their dma-buf mappings, so
their essentially pinned forever from first use on. Userptr won't
really make this worse, but imo we should fix this first before
expanding the use-cases too much. And getting dma-bufs to integrate
better into existing memory mangers like ttm will be a lot of pain.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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