Query for inter-process buffer sharing

Hello, 

How do you think about adding a new callback function which makes allocator
for vb2 fill the reserved field in v4l2_buffer as below.
As-Is:  VIDIOC_QUERYBUF -> v4l2_m2m_querybuf -> vb2_querybuf ->
__fill_v4l2_buffer
To-Be: VIDIOC_QUERYBUF -> v4l2_m2m_querybuf -> vb2_querybuf ->
__fill_v4l2_buffer + vb2_mem_ops.fill_v4l2_buffer

I want to use the reserved field as for process unique key to share the
buffer between inter-process.
When I want to send a buffer which is allocated by A device to other
process, I want to get the process unique key from VIDIOC_QUERYBUF.
The process which gets the process unique key from other process will make
user virtual address from the key in any other way.
And then send it to B device using QBUF with USERPTR buffer type.

How do you think about this concept ?


      Process A
Process B

1. VIDIOC_QUERYBUF to get the process unique key 

2. VIDIOC_DQBUF

3. Send the process unique key to Process B
----------------------------------->    Process unique key

						                  4. Make a
user virtual address from the process unique key

                                                                       5.
VIDIOC_QBUF with user virtual address

                                                                       6.
find the paddr or device address from the user virtual addr. in videobuf2

                                                                       7.
H/W operation.

SCM_RIGHTS can be the solution for inter-process buffer sharing.
http://blog.toidinamai.de/en/programming/SCM_RIGHTS
But it has risk that other process can also control the device using the
shared file descriptor.
So I'm trying to make another solution.

Best regards,