c8fcf7a91d
Every port probing will have the Generic plugin as fallback, and due to some
other issues in other plugins (see ee099fcd), we need to allow overwriting the
suggested plugin from the Generic to a more specific one.
One of the drawbacks of this is that we're actually allowing the Generic plugin
to probe and accept the port, which means that the generic plugin may accept a
specific port type (e.g. QMI) while the specific plugin wouldn't. So, we will
now also run the subsystems filter before grabbing the specific port, in order
to really filter out those cases. We still keep the subsystems filter in
pre-probing, so that we build a better initial plugin list to probe.
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!