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We previously had the modem initialization command merged with some other port setup commands in the 'modem_init' step of the 'Modem' interface. Instead of doing this, we now split the logic into two separate steps: A first 'enabling_modem_init' modem initialization step is to be run just after the ports have been opened, but only during the first enabling operation, and only if the modem was not hotplugged. A hotplugged modem is assumed to be properly initialized already, so no need to ATZ-it. Also, we will now wait 500ms by default after the modem initialization command has been sent, to let it settle down. The second 'modem_init' step will be run during the 'Modem' interface initialization, and it currently only holds specific setup of the primary and secondary serial ports. We'll be modifying this logic a bit in the next commits, so no big deal to have that step name unchanged.
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!