Re: [media] uvcvideo: support for contiguous DMA buffers

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Vincent,

(CC'ing Nicolas)

On Monday 09 Jan 2017 15:49:00 Vincent ABRIOU wrote:
> On 01/09/2017 04:37 PM, Laurent Pinchart wrote:
> > Hi Vincent,
> > 
> > Thank you for the patch.
> > 
> > On Monday 03 Oct 2016 13:27:16 Vincent Abriou wrote:
> >> Allow uvcvideo compatible devices to allocate their output buffers using
> >> contiguous DMA buffers.
> > 
> > Why do you need this ? If it's for buffer sharing with a device that
> > requires dma-contig, can't you allocate the buffers on the other device
> > and import them on the UVC side ?
> 
> Hi Laurent,
> 
> I need this using Gstreamer simple pipeline to connect an usb webcam
> (v4l2src) with a display (waylandsink) activating the zero copy path.
> 
> The waylandsink plugin does not have any contiguous memory pool to
> allocate contiguous buffer. So it is up to the upstream element, here
> v4l2src, to provide such contiguous buffers.

Isn't that a gstreamer issue ?

> >> Add the "allocators" module parameter option to let uvcvideo use the
> >> dma-contig instead of vmalloc.
> >> 
> >> Signed-off-by: Vincent Abriou <vincent.abriou@st.com>
> >> ---
> >> 
> >>  Documentation/media/v4l-drivers/uvcvideo.rst | 12 ++++++++++++
> >>  drivers/media/usb/uvc/Kconfig                |  2 ++
> >>  drivers/media/usb/uvc/uvc_driver.c           |  3 ++-
> >>  drivers/media/usb/uvc/uvc_queue.c            | 23 ++++++++++++++++++---
> >>  drivers/media/usb/uvc/uvcvideo.h             |  4 ++--
> >>  5 files changed, 38 insertions(+), 6 deletions(-)

-- 
Regards,

Laurent Pinchart