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* 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.
ModemManager. The problem ModemManager tries to solve is to provide a unified high level API for communicating with (mobile broadband) modems. While the basic commands are standardized, the more advanced operations (like signal quality monitoring while connected) varies a lot. Using. ModemManager is a system daemon and is not meant to be used directly from the command line. However, since it provides DBus API, it is possible to use 'dbus-send' command to control it from the terminal. There's an example program (tests/mm-test.py) that demonstrates the basic API usage. Implementation. ModemManager is a DBus system bus activated service (meaning it's started automatically when a request arrives). It is written in C. The devices are queried from udev and automatically updated based on hardware events. There's a GInterface (MMModem) that defines the modem interface and any device specific implementation must implement it. There are two generic MMModem implementations to support the basic operations (one for GSM, one for CDMA,) which are common for all cards. Plugins. Plugins are loaded on startup, and must implement the MMPlugin interface. It consists of a couple of methods which tell the daemon whether the plugin supports a port and to create custom MMModem implementations. It most likely makes sense to derive custom modem implementations from one of the generic classes and just add (or override) operations which are not standard. There's a fully working plugin in the plugins/ directory for Huawei cards that can be used as an example for writing new plugins. Writing new plugins is highly encouraged! API. The API is open for changes, so if you're writing a plugin and need to add or change some public method, feel free to suggest it!