Hi all,
I've been converting a Cisco internal driver to vb2 and while doing that I
found a few issues.
1) I noticed that struct vb2_buffer doesn't have a list_head that the driver
can use to hook it in its dma queue. That forces you to make your own
buffer struct just to have your own list_head.
I think vb2_buffer should either get a driver_entry or the 'done_entry' field
can be assigned for driver use (since a buffer can't be owned by the driver
and be on the done list at the same time). I abused 'done_entry' for now.
2) videobuf2-dma-sg.c no longer calls dma_(un)map_sg()! The old
videobuf-dma-sg.c did that for you. Is there any reason for this change?
I had to manually add it to my driver.
3) videobuf2-core.c uses this in __fill_v4l2_buffer:
if (vb->num_planes_mapped == vb->num_planes)
b->flags |= V4L2_BUF_FLAG_MAPPED;
However, I see no code that ever decreases num_planes_mapped. And I also
wonder what happens if vb2_mmap is called multiple times: num_planes_mapped
will be increased so vb->num_planes_mapped > vb->num_planes and the MAPPED
flag is no longer set.
This is a particular problem with libv4l2 since that tests for the MAPPED
flag and will refuse e.g. format changes if it is set.
4) It is not clear to me when vb2_queue_release should be called. Is it in
close() when you close a filehandle that was used for streaming?
Regards,
Hans
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