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
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