* mm_base_modem_peek_port_* () will return either a port object (no new
reference), or NULL if none available.
You would usually peek() a port if you're going to use it just in the current
method, as there is no way to that reference to get invalid (we're single
threaded).
* mm_base_modem_get_port_* () will return either NEW references to valid
port objects, or NULL if none available.
And, you would usually get() a port, whenever you want the port object to be
valid even out of the current method, for example when keeping it in the
context of an async operation.
Also, we need to consider that the primary AT port MAY BE NULL when you
peek() or get() it. This is due to the fact that we may be releasing ports
(due to device disconnection) in the middle of async operations.
Modems may get notified via unsolicited messages (either AT or QMI or some
other thing), that the network time was updated. This setup allows subclasses
implementing the Time interface to setup/cleanup and enable/disable the
unsolicited messages, as well as notify about the network time updates.
Following the same logic as in the original implementation, we try to load the
network timezone information only after being registered, and also with up to N
retries. The async operation in charge of the loading can be cancelled
gracefully, i.e. if the interface is disabled before we get ever registered.
Aleksander Morgado