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This ensure that the buffer pool won't always discard buffer with these
memory when they are released.

This ensure that a flushed group memory are the same size as when they
where originally allocated / imported.

The value of num_allocated buffer would get confused when
buffer are being discarded.

Need to include config.h, otherwise we endup directly using the
ioct/mmap/munmap calls and need to vall v4l2_munmap.

We where not setting the probed flags on the allocator, which mean even if
CREATE_BUFS was supported on some driver, it would endup being ignored.

Return a buffer from an otherpool has unwanted side effects that lead to leaks and
prevents deactivating the pool. Instead, we change the _process() API so it can
replace the internal buffer with the buffer from the downstream pool. This implied
moving from _fill() to _create() method in the src.

The acquire is done in _prepare now.

Buffer refcounting is a bit hard, because of the duality between CAPTURE and
OUTPUT mode. In the long term, we should consider having two seperate pool
instead of this mess. At least state should be better kept this way.

All enum that has REQBUFS and CREATE_BUFS where missing S, which was
confusing since they are supposed to match with associcated ioctl name. This
also fixes the yet unused CAN_REQUEST flag check.

Rather then hard failure, we should update the config with the meta option we
need and return false.

parse_nth_allocation_pool() give a ref on the pool, we need to unref it
when done.

This can be enabled sing io-mode=dmabuf. This will enabled mmap base
drivers to export the buffers as dmabuf.

Because of the buf in videobuf2, dqbuf may leave the DONE flag being,
which would implied that the buffer is queued. As this has been broken
for 4 years, simply guaranty the state flags integrity when doing
qbuf/dqbuf.

See https://patchwork.linuxtv.org/patch/23641/

In set_caps, now checks if caps actually changed and succeed if they didn't
change.

Improve decide allocation so it properly configure both local and downstream
buffer pools. Also read back the pool config if it was changed to to driver
limitations.

Pre-configuring the pool is error prone, since it may hide a configuration failure and
endup with a pool that is not configured the way it should (e.g. no video meta, wrong
queue size, etc.)

Turn crop meta into a custom option and make sure it's there is needed.

Catch short allocation after saving the format. This is not a catch all, but should catch
most of the miss-behaving drivers when doing S_FMT/G_FMT and avoid potential crash.

This goal of this allocator is mainly to allow tracking the memory.
Currently, when a buffer memory has been modified, the buffer and it's
memory is disposed and lost until the stream is restarted.

Currently we advertise crop meta, but not element handle support this meta.