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From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To: "Rémi Denis-Courmont" <remi@remlab.net>
Cc: Hans Verkuil <hverkuil@xs4all.nl>,
	Tomasz Stanislawski <t.stanislaws@samsung.com>,
	linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org,
	airlied@redhat.com, m.szyprowski@samsung.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,
	subashrp@gmail.com, mchehab@redhat.com, g.liakhovetski@gmx.de
Subject: Re: [PATCHv2 3/9] v4l: add buffer exporting via dmabuf
Date: Tue, 31 Jul 2012 23:52:35 +0200	[thread overview]
Message-ID: <1376487.cHbjGZJEZg@avalon> (raw)
In-Reply-To: <201207312139.42818.remi@remlab.net>

Hi Rémi,

On Tuesday 31 July 2012 21:39:40 Rémi Denis-Courmont wrote:
> Le mardi 31 juillet 2012 19:28:12 Laurent Pinchart, vous avez écrit :
> > On Tuesday 31 July 2012 16:39:00 Rémi Denis-Courmont wrote:
> > > Le mardi 31 juillet 2012 14:56:14 Laurent Pinchart, vous avez écrit :
> > > > > For that matter, wouldn't it be useful to support exporting a
> > > > > userptr
> > > > > buffer at some point in the future?
> > > > 
> > > > Shouldn't USERPTR usage be discouraged once we get dma-buf support ?
> > > 
> > > USERPTR, where available, is currently the only way to perform zero-copy
> > > from kernel to userspace. READWRITE does not support zero-copy at all.
> > > MMAP only supports zero-copy if userspace knows a boundary on the number
> > > of concurrent buffers *and* the device can deal with that number of
> > > buffers; in general, MMAP requires memory copying.
> > 
> > Could you please share your use case(s) with us ?
> 
> I want to receive the video buffers in user space for processing. Typically
> "processing" is software encoding or conversion. That's what virtually any
> V4L application does on the desktop...

But what prevents you from using MMAP ?

-- 
Regards,

Laurent Pinchart


  reply	other threads:[~2012-07-31 21:52 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-06-14 14:32 [PATCHv2 0/9] Support for dmabuf exporting for videobuf2 Tomasz Stanislawski
2012-06-14 14:32 ` Tomasz Stanislawski
2012-06-14 14:32 ` [PATCHv2 1/9] v4l: vb2-dma-contig: let mmap method to use dma_mmap_coherent call Tomasz Stanislawski
2012-06-14 14:32 ` [PATCHv2 2/9] Documentation: media: description of DMABUF exporting in V4L2 Tomasz Stanislawski
2012-06-14 14:32 ` [PATCHv2 3/9] v4l: add buffer exporting via dmabuf Tomasz Stanislawski
2012-07-31  6:33   ` Hans Verkuil
2012-07-31 11:56     ` Laurent Pinchart
2012-07-31 12:11       ` Hans Verkuil
2012-07-31 12:46         ` Rob Clark
2012-08-01  8:01         ` Tomasz Stanislawski
2012-08-01  8:10           ` Laurent Pinchart
2012-08-01  8:28           ` Hans Verkuil
2012-08-01  9:35             ` Tomasz Stanislawski
2012-07-31 13:39       ` Rémi Denis-Courmont
2012-07-31 14:03         ` Rob Clark
2012-07-31 14:18           ` Rémi Denis-Courmont
2012-07-31 16:28         ` Laurent Pinchart
2012-07-31 18:39           ` Rémi Denis-Courmont
2012-07-31 21:52             ` Laurent Pinchart [this message]
2012-08-01  8:37               ` Rémi Denis-Courmont
2012-08-01  8:37                 ` Rémi Denis-Courmont
2012-08-01 11:35                 ` Laurent Pinchart
2012-08-01 20:49                   ` Rémi Denis-Courmont
2012-08-02  6:35                     ` Hans Verkuil
2012-08-02  6:56                       ` Rémi Denis-Courmont
2012-08-02  7:08                         ` Hans Verkuil
2012-08-02 21:50                           ` Laurent Pinchart
2012-08-02 21:41                         ` Laurent Pinchart
2012-08-08  9:35                       ` Sakari Ailus
2012-08-08  9:46                         ` Hans Verkuil
2012-06-14 14:32 ` [PATCHv2 4/9] v4l: vb2: " Tomasz Stanislawski
2012-06-14 14:32 ` [PATCHv2 5/9] v4l: vb2-dma-contig: add support for DMABUF exporting Tomasz Stanislawski
2012-06-14 14:32 ` [PATCHv2 6/9] v4l: s5p-fimc: support for dmabuf exporting Tomasz Stanislawski
2012-06-14 14:32 ` [PATCHv2 7/9] v4l: s5p-tv: mixer: " Tomasz Stanislawski
2012-06-14 14:32 ` [PATCHv2 8/9] v4l: s5p-mfc: " Tomasz Stanislawski
2012-06-14 14:32 ` [PATCHv2 9/9] v4l: vb2-dma-contig: use dma_get_sgtable Tomasz Stanislawski

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