From: "Rémi Denis-Courmont" <remi@remlab.net>
To: Hans Verkuil <hverkuil@xs4all.nl>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
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: Thu, 2 Aug 2012 09:56:43 +0300 [thread overview]
Message-ID: <201208020956.45291.remi@remlab.net> (raw)
In-Reply-To: <201208020835.58332.hverkuil@xs4all.nl>
Le jeudi 2 août 2012 09:35:58 Hans Verkuil, vous avez écrit :
> On Wed August 1 2012 22:49:57 Rémi Denis-Courmont wrote:
> > > What about using the CREATE_BUFS ioctl to add new MMAP buffers at
> > > runtime ?
> >
> > Does CREATE_BUFS always work while already streaming has already started?
> > If it depends on the driver, it's kinda helpless.
>
> Yes, it does. It's one of the reasons it exists in the first place. But
> there are currently only a handful of drivers that implement it. I hope
> that as more and more drivers are converted to vb2 that the availability
> of create_bufs will increase.
That's contradictory. If most drivers do not support it, then it won't work
during streaming.
> > What's the guaranteed minimum buffer count? It seems in any case, MMAP
> > has a hard limit of 32 buffers (at least videobuf2 has), though one
> > might argue this should be more than enough.
>
> Minimum or maximum? The maximum is 32, that's hardcoded in the V4L2 core.
> Although drivers may force a lower maximum if they want. I have no idea
> whether there are drivers that do that. There probably are.
The smallest of the maxima of all drivers.
> The minimum is usually between 1 and 3, depending on hardware limitations.
And that's clearly insufficient without memory copy to userspace buffers.
It does not seem to me that CREATE_BUFS+MMAP is a useful replacement for
REQBUFS+USERBUF then.
--
Rémi Denis-Courmont
http://www.remlab.net/
http://fi.linkedin.com/in/remidenis
next prev parent reply other threads:[~2012-08-02 6:56 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
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 [this message]
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=201208020956.45291.remi@remlab.net \
--to=remi@remlab.net \
--cc=airlied@redhat.com \
--cc=daeinki@gmail.com \
--cc=daniel.vetter@ffwll.ch \
--cc=dri-devel@lists.freedesktop.org \
--cc=g.liakhovetski@gmx.de \
--cc=hverkuil@xs4all.nl \
--cc=kyungmin.park@samsung.com \
--cc=laurent.pinchart@ideasonboard.com \
--cc=linaro-mm-sig@lists.linaro.org \
--cc=linux-media@vger.kernel.org \
--cc=m.szyprowski@samsung.com \
--cc=mchehab@redhat.com \
--cc=pawel@osciak.com \
--cc=robdclark@gmail.com \
--cc=subashrp@gmail.com \
--cc=sumit.semwal@ti.com \
--cc=t.stanislaws@samsung.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.