[Linaro-mm-sig] [PATCHv6 00/13] Integration of videobuf2 with dmabuf

[Hans Verkuil]

On Mon June 4 2012 23:58:07 Hans Verkuil wrote:
> Hi Rebecca,
> 
> On Mon June 4 2012 21:34:23 Rebecca Schultz Zavin wrote:
> > I have a system where the data is planar, but the kernel drivers
> > expect to get one allocation with offsets for the planes.  I can't
> > figure out how to do that with the current dma_buf implementation.  I
> > thought I could pass the same dma_buf several times and use the
> > data_offset field of the v4l2_plane struct but it looks like that's
> > only for output.  Am I missing something?  Is this supported?
> 
> v4l2_plane is typically used if the planes are allocated separately.
> If you allocate it in one go, aren't the planes then at well-defined
> offsets from the start? If so, then it is either one of the already
> pre-defined planar formats found here:
> 
> http://hverkuil.home.xs4all.nl/spec/media.html#yuv-formats
> 
> or you define a pixelformat specific to your own hardware that identifies
> that particular format.
> 
> If it is one allocation, but there is no clear calculation based on width
> and height that gives you the start of each plane, then we do not support
> that at the moment. I believe I had a discussion about something similar
> with people from Qualcomm, but that never came to anything.

It took some digging, but this was the enhancement proposed for a Qualcomm
problem:

http://www.spinics.net/lists/linux-media/msg40376.html

This may or may not be what you are looking for.

Regards,

	Hans

> 
> That would be something to discuss on the linux-media mailinglist.
> 
> Regards,
> 
> 	Hans
> 
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