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From: Marek Szyprowski <m.szyprowski@samsung.com>
To: "'Mauro Carvalho Chehab'" <mchehab@redhat.com>,
	"'Rémi Denis-Courmont'" <remi@remlab.net>
Cc: Tomasz Stanislawski <t.stanislaws@samsung.com>,
	'Laurent Pinchart' <laurent.pinchart@ideasonboard.com>,
	linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org,
	airlied@redhat.com, kyungmin.park@samsung.com,
	sumit.semwal@ti.com, daeinki@gmail.com, daniel.vetter@ffwll.ch,
	robdclark@gmail.com, pawel@osciak.com,
	linaro-mm-sig@lists.linaro.org, hverkuil@xs4all.nl,
	subashrp@gmail.com
Subject: RE: [PATCH v4 02/14] Documentation: media: description of DMABUF importing in V4L2
Date: Mon, 23 Apr 2012 09:50:05 +0200	[thread overview]
Message-ID: <056501cd2125$b286d5e0$179481a0$%szyprowski@samsung.com> (raw)
In-Reply-To: <4F916660.7040608@redhat.com>

Hi Mauro,

On Friday, April 20, 2012 3:37 PM Mauro Carvalho Chehab wrote:

(snipped)

> >> So my rough-idea was to remove USERPTR support from kernel
> >> drivers (if possible of course) and to provide an emulation
> >> layer in the userspace code like libv4l2.
> >>
> >> Please note that it is only a rough idea. Just brainstorming :)
> 
> > It is *too early* to start any discussion on this topic.
> > Especially until DMABUF is mature enough to become a good
> > alternative for userptr.
> 
> Looking at the hole picture, dropping USERPTR would only make
> sense if it is broken on dev2user (or user2dev) transfers.
> 
> Dropping its usage on dev2dev transfers makes sense, after having
> DMABUF implemented.
> 
> Yet, if some userspace application wants to abuse of USERPTR in order
> to use it for dev2dev transfer, there's not much that can be done at
> Kernel level.
> 
> It makes sense to put a big warn at the V4L2 Docs telling that this
> is not officially supported and can cause all sorts of issues at
> the machine/system.

Please note that all current drivers which use videobuf/videobuf2-dma-contig
are able to use userptr memory access method only with physically contiguous
memory. This means that in fact they work only buffers, which come from other
devices and dev2dev transfers are the only possibility. malloc()ed memory
buffers are rejected.

Best regards
-- 
Marek Szyprowski
Samsung Poland R&D Center




  reply	other threads:[~2012-04-23  7:50 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-04-13 15:47 [PATCH v4 00/14] Integration of videobuf2 with dmabuf Tomasz Stanislawski
2012-04-13 15:47 ` [PATCH v4 01/14] v4l: Add DMABUF as a memory type Tomasz Stanislawski
2012-04-17  0:57   ` Laurent Pinchart
2012-04-13 15:47 ` [PATCH v4 02/14] Documentation: media: description of DMABUF importing in V4L2 Tomasz Stanislawski
2012-04-16 23:25   ` Laurent Pinchart
2012-04-19 14:32     ` Tomasz Stanislawski
2012-04-19 20:36       ` Mauro Carvalho Chehab
2012-04-19 20:37       ` Mauro Carvalho Chehab
2012-04-20  8:41         ` Tomasz Stanislawski
2012-04-20 10:56           ` Rémi Denis-Courmont
2012-04-20 10:56             ` Rémi Denis-Courmont
2012-04-20 12:25             ` Tomasz Stanislawski
2012-04-20 13:03               ` Rémi Denis-Courmont
2012-04-20 13:03                 ` Rémi Denis-Courmont
2012-04-21 17:10                 ` Laurent Pinchart
2012-04-20 14:48               ` Mauro Carvalho Chehab
2012-04-20 13:36             ` Mauro Carvalho Chehab
2012-04-23  7:50               ` Marek Szyprowski [this message]
2012-04-23 14:00                 ` Mauro Carvalho Chehab
2012-04-13 15:47 ` [PATCH v4 03/14] v4l: vb2: add support for shared buffer (dma_buf) Tomasz Stanislawski
2012-04-17  0:57   ` Laurent Pinchart
2012-04-13 15:47 ` [PATCH v4 04/14] v4l: vb: remove warnings about MEMORY_DMABUF Tomasz Stanislawski
2012-04-17  0:57   ` Laurent Pinchart
2012-04-13 15:47 ` [PATCH v4 05/14] v4l: vb2-dma-contig: Shorten vb2_dma_contig prefix to vb2_dc Tomasz Stanislawski
2012-04-13 15:47 ` [PATCH v4 06/14] v4l: vb2-dma-contig: Remove unneeded allocation context structure Tomasz Stanislawski
2012-04-17  0:57   ` Laurent Pinchart
2012-04-13 15:47 ` [PATCH v4 07/14] v4l: vb2-dma-contig: Reorder functions Tomasz Stanislawski
2012-04-13 15:47 ` [PATCH v4 08/14] v4l: vb2-dma-contig: add support for scatterlist in userptr mode Tomasz Stanislawski
2012-04-17  0:43   ` Laurent Pinchart
2012-04-17  0:43     ` Laurent Pinchart
2012-04-20  8:52     ` Tomasz Stanislawski
2012-04-13 15:47 ` [PATCH v4 09/14] v4l: vb2: add prepare/finish callbacks to allocators Tomasz Stanislawski
2012-04-17  0:57   ` Laurent Pinchart
2012-04-13 15:47 ` [PATCH v4 10/14] v4l: vb2-dma-contig: add prepare/finish to dma-contig allocator Tomasz Stanislawski
2012-04-13 15:47 ` [PATCH v4 11/14] v4l: vb2-dma-contig: add support for dma_buf importing Tomasz Stanislawski
2012-04-17  0:57   ` Laurent Pinchart
2012-04-17  0:57     ` Laurent Pinchart
2012-04-19 11:38     ` Tomasz Stanislawski
2012-04-13 15:47 ` [PATCH v4 12/14] v4l: vb2-dma-contig: change map/unmap behaviour for importers Tomasz Stanislawski
2012-04-17  1:03   ` Laurent Pinchart
2012-04-13 15:47 ` [PATCH v4 13/14] v4l: s5p-tv: mixer: support for dmabuf importing Tomasz Stanislawski
2012-04-13 15:47 ` [PATCH v4 14/14] v4l: fimc: " Tomasz Stanislawski
2012-04-20 12:56   ` Sylwester Nawrocki

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