From: Marek Szyprowski <m.szyprowski@samsung.com>
To: Pawel Osciak <pawel@osciak.com>
Cc: Tomasz Stanislawski <t.stanislaws@samsung.com>,
linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org,
airlied@redhat.com, kyungmin.park@samsung.com,
laurent.pinchart@ideasonboard.com, sumit.semwal@ti.com,
daeinki@gmail.com, daniel.vetter@ffwll.ch, robdclark@gmail.com,
linaro-mm-sig@lists.linaro.org, hverkuil@xs4all.nl,
remi@remlab.net, subashrp@gmail.com, mchehab@redhat.com,
zhangfei.gao@gmail.com, s.nawrocki@samsung.com,
k.debski@samsung.com
Subject: Re: [PATCHv10 08/26] v4l: vb2-dma-contig: add support for scatterlist in userptr mode
Date: Tue, 30 Oct 2012 07:43:44 +0100 [thread overview]
Message-ID: <508F7720.5080606@samsung.com> (raw)
In-Reply-To: <CAMm-=zB9-WJ5b6Xku1UwvG4UZOGQ_V6pKFT4C_Xf0kF-O+VDdw@mail.gmail.com>
Hello,
On 10/26/2012 6:24 PM, Pawel Osciak wrote:
> Hi Tomasz,
>
> On Wed, Oct 10, 2012 at 7:46 AM, Tomasz Stanislawski
> <t.stanislaws@samsung.com> wrote:
>> This patch introduces usage of dma_map_sg to map memory behind
>> a userspace pointer to a device as dma-contiguous mapping.
>>
>
> Perhaps I'm missing something, but I don't understand the purpose of
> this patch. If the device can do DMA SG, why use videobuf2-dma-contig
> and not videobuf2-dma-sg?
This patch is for devices which doesn't do DMA SG, but might be behind
IOMMU. In such case one can call dma_map_sg() with scatterlist of
individual pages gathered from user pointer (anonymous memory of the
process) which in turn will be mapped into contiguous dma adress space
(dma_map_sg() returns only one chunk in such case). This is not very
intuitive, but it was best way to fit such case into existing
dma-mapping design.
> What would be the difference design-wise
> between them if this patch is merged?
Best regards
--
Marek Szyprowski
Samsung Poland R&D Center
next prev parent reply other threads:[~2012-10-30 6:43 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-10 14:46 [PATCHv10 00/26] Integration of videobuf2 with DMABUF Tomasz Stanislawski
2012-10-10 14:46 ` [PATCHv10 01/26] v4l: Add DMABUF as a memory type Tomasz Stanislawski
2012-10-10 14:46 ` [PATCHv10 02/26] Documentation: media: description of DMABUF importing in V4L2 Tomasz Stanislawski
2012-10-15 7:53 ` Hans Verkuil
2012-10-10 14:46 ` [PATCHv10 03/26] v4l: vb2: add support for shared buffer (dma_buf) Tomasz Stanislawski
2012-10-10 14:46 ` [PATCHv10 04/26] v4l: vb: remove warnings about MEMORY_DMABUF Tomasz Stanislawski
2012-10-10 14:46 ` [PATCHv10 05/26] v4l: vb2-dma-contig: shorten vb2_dma_contig prefix to vb2_dc Tomasz Stanislawski
2012-10-10 14:46 ` [PATCHv10 06/26] v4l: vb2-dma-contig: remove reference of alloc_ctx from a buffer Tomasz Stanislawski
2012-10-10 14:46 ` [PATCHv10 07/26] v4l: vb2-dma-contig: reorder functions Tomasz Stanislawski
2012-10-10 14:46 ` [PATCHv10 08/26] v4l: vb2-dma-contig: add support for scatterlist in userptr mode Tomasz Stanislawski
2012-10-26 16:24 ` Pawel Osciak
2012-10-30 6:43 ` Marek Szyprowski [this message]
2012-10-10 14:46 ` [PATCHv10 09/26] v4l: vb2: add prepare/finish callbacks to allocators Tomasz Stanislawski
2012-10-10 14:46 ` [PATCHv10 10/26] v4l: vb2-dma-contig: add prepare/finish to dma-contig allocator Tomasz Stanislawski
2012-10-10 14:46 ` [PATCHv10 11/26] v4l: vb2-dma-contig: add support for dma_buf importing Tomasz Stanislawski
2012-10-10 14:46 ` [PATCHv10 12/26] v4l: vb2-vmalloc: add support for dmabuf importing Tomasz Stanislawski
2012-10-10 14:46 ` [PATCHv10 13/26] v4l: vivi: " Tomasz Stanislawski
2012-10-10 14:46 ` [PATCHv10 14/26] v4l: s5p-tv: mixer: " Tomasz Stanislawski
2012-10-10 14:46 ` [PATCHv10 15/26] v4l: s5p-fimc: " Tomasz Stanislawski
2012-10-10 14:46 ` [PATCHv10 16/26] v4l: vb2-dma-contig: let mmap method to use dma_mmap_coherent call Tomasz Stanislawski
2012-10-10 14:46 ` [PATCHv10 17/26] Documentation: media: description of DMABUF exporting in V4L2 Tomasz Stanislawski
2012-10-15 7:59 ` Hans Verkuil
2012-10-10 14:46 ` [PATCHv10 18/26] v4l: add buffer exporting via dmabuf Tomasz Stanislawski
2012-10-15 8:01 ` Hans Verkuil
2012-10-10 14:46 ` [PATCHv10 19/26] v4l: vb2: " Tomasz Stanislawski
2012-10-10 14:46 ` [PATCHv10 20/26] v4l: vb2-dma-contig: add support for DMABUF exporting Tomasz Stanislawski
2012-10-11 21:46 ` Laurent Pinchart
2012-10-10 14:46 ` [PATCHv10 21/26] v4l: vb2-dma-contig: add reference counting for a device from allocator context Tomasz Stanislawski
2012-10-11 21:49 ` Laurent Pinchart
2012-10-12 6:28 ` Tomasz Stanislawski
2012-10-12 9:32 ` Laurent Pinchart
2012-10-10 14:46 ` [PATCHv10 22/26] v4l: vb2-dma-contig: fail if user ptr buffer is not correctly aligned Tomasz Stanislawski
2012-10-11 21:36 ` Laurent Pinchart
2012-10-12 7:44 ` Tomasz Stanislawski
2012-10-12 7:58 ` Hans Verkuil
2012-10-12 9:34 ` Laurent Pinchart
2012-10-10 14:46 ` [PATCHv10 23/26] v4l: vb2-dma-contig: align buffer size to PAGE_SIZE Tomasz Stanislawski
2012-10-11 21:31 ` Laurent Pinchart
2012-10-12 8:24 ` Tomasz Stanislawski
2012-10-16 12:22 ` Laurent Pinchart
2012-10-10 14:46 ` [PATCHv10 24/26] v4l: s5p-fimc: support for dmabuf exporting Tomasz Stanislawski
2012-10-10 14:46 ` [PATCHv10 25/26] v4l: s5p-tv: mixer: " Tomasz Stanislawski
2012-10-10 14:46 ` [PATCHv10 26/26] v4l: s5p-mfc: " Tomasz Stanislawski
2012-11-08 12:05 ` [PATCH 27/26] v4l: vb2: Set data_offset to 0 for single-plane buffers Laurent Pinchart
2012-11-08 12:13 ` Marek Szyprowski
2012-11-08 12:19 ` Laurent Pinchart
2012-11-08 15:28 ` Tomasz Stanislawski
2012-11-08 16:36 ` Laurent Pinchart
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=508F7720.5080606@samsung.com \
--to=m.szyprowski@samsung.com \
--cc=airlied@redhat.com \
--cc=daeinki@gmail.com \
--cc=daniel.vetter@ffwll.ch \
--cc=dri-devel@lists.freedesktop.org \
--cc=hverkuil@xs4all.nl \
--cc=k.debski@samsung.com \
--cc=kyungmin.park@samsung.com \
--cc=laurent.pinchart@ideasonboard.com \
--cc=linaro-mm-sig@lists.linaro.org \
--cc=linux-media@vger.kernel.org \
--cc=mchehab@redhat.com \
--cc=pawel@osciak.com \
--cc=remi@remlab.net \
--cc=robdclark@gmail.com \
--cc=s.nawrocki@samsung.com \
--cc=subashrp@gmail.com \
--cc=sumit.semwal@ti.com \
--cc=t.stanislaws@samsung.com \
--cc=zhangfei.gao@gmail.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.