The icmsg and icmsg_me backends has limitations in context of
concurrent access to single instance. Some limitations are:
* sending by more thread at the same time may cause -EBUSY
* allocating TX buffer will cause errors in other threads that want
to allocate before first thread sent the message,
* during no-copy receive, when RX buffer is on hold receiving is
totally blocked.
This backend resolves those limitations by adding dynamically allocated
buffers on shared memory next to ICmsg circular buffer. The data is
passed using those buffers, so concurrency is not a problem. The ICmsg
is used only to pass short 2-byte messages containing references to
those buffers. The backend also supports multiple endpoint.
The ipc/icmsg_me sample was modified to support this backend.
Signed-off-by: Dominik Kilian <Dominik.Kilian@nordicsemi.no>
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