videobuf2-dma-sg and multiple planes semantics

[Robert Jarzmik <robert.jarzmik@free.fr>]

Hi,

I've been converting pxa_camera driver from videobuf to videobuf2, and I have a
question about multiple plane semantics.

I have a case where I have 3 planes for a yuv422 capture :
 - 1 Y plane (total_size / 2 bytes)
 - 1 U plane (total_size / 4 bytes)
 - 1 V plane (total_size / 4 bytes)

I would have expected vb2_dma_sg_plane_desc(vb, i) to return me 3 different
sg_tables, one for each plane. I would have been then able to feed them to 3
dmaengine channels (this is the case for pxa27x platform), so that the 3 planes
are filled in concurrently.

My understanding is that videobuf2-dma-sg has only 1 sg_table, which seems to be
enforced by vb2_dma_sg_cookie(), so the question is : is it on purpose, and how
do the multiple planes are handled within videobuf2-dma-sg ?

Cheers.

--
Robert