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

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

Hi Rebecca,

On Monday 04 June 2012 12:34:23 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?

data_offset is indeed for video output only at the moment, and doesn't seem to 
be used by any driver in mainline for now.

I can't really see a reason why data_offset couldn't be used for video capture 
devices as well.

Sanity checks are currently missing. For output devices we should check that 
data_offset + bytesused < length in the vb2 core. For input devices the check 
will have to be performed by drivers. Taking data_offset into account 
automatically would also be useful. I think most of that should be possible to 
implement in the allocators.

-- 
Regards,

Laurent Pinchart