The big advantage of using poll() in application is the possibility to listen for multiple events at once such as:
- incoming traffic on BSD socket,
- incoming traffic on other socket type (e.g. pipe, socketpair),
- some event from other application thread/component using eventfd(),
- some timeouts using timerfd (not implemented in Zephyr yet, but it seems just a matter of time).
Current implementation of offloaded poll() for nRF91 modem sockets uses nrf_poll() underneath. This means that only modem sockets (file descriptors) are handled using such poll() call (and most mechanisms mentioned above do not). This is enough only for some simple usage, but is very limiting when application requires some complex behavior based on other application threads or traffic from other network interfaces.
We need to have for example some callback based mechanism for getting notifications from nRF sockets. That way those notifications can be easily integrated with Zephyr native poll() mechanism, which handles all possible socket types and allows implementation of much more advanced application code and possibly integration with higher number of existing POSIX-compatible libraries.
