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Port serial command completions may be performed in several different places: * When a cached response is set during command sending. * When errors happen during command sending. * When we process a response (i.e. common_input_available()) * When we process a timeout (i.e. port_serial_timed_out()) * When cancelled (i.e. port_serial_response_wait_cancelled()) We're currently safe with the previous logic only because the users of the serial port explicitly complete operations in idle, which means that whenever we're processing in a internal callback (e.g. during response or timeout processing) the serial port object is valid for as long as the callback runs. But, if we ever end up using the serial port with a not-in-idle completion, it may happen that if the command is completed within a internal signal callback the serial port object may get fully closed and unref-ed before exiting the callback. We could force a valid port reference to exist as long as the internal signal is scheduled, but then we may lose the ability to automatically close the port during a full unref(), as the internal signals are set as long as the port is open. So, to cope with this possibility of not-in-idle completion, we instead force references to be valid whenever we see that a command completion may happen, which is basically whenever port_serial_got_response() is called; but we only do that if we're going to use the port object after that, otherwise, we ignore the problem. In addition to the problems with the references, we also update the common_input_available() method so that the source isn't kept if the last response buffer processing ended up closing the port.
ModemManager. ModemManager provides a unified high level API for communicating with mobile broadband modems, regardless of the protocol used to communicate with the actual device (Generic AT, vendor-specific AT, QCDM, QMI, MBIM...). Using. ModemManager is a system daemon and is not meant to be used directly from the command line. However, since it provides a DBus API, it is possible to use 'dbus-send' commands or the new 'mmcli' command line interface to control it from the terminal. The devices are queried from udev and automatically updated based on hardware events, although a manual re-scan can also be requested to look for RS232 modems. Implementation. ModemManager is a DBus system bus activated service (meaning it's started automatically when a request arrives). It is written in C, using glib and gio. Several GInterfaces specify different features that the modems support, including the generic MMIfaceModem3gpp and MMIfaceModemCdma which provice basic operations for 3GPP (GSM, UMTS, LTE) or CDMA (CDMA1x, EV-DO) modems. If a given feature is not available in the modem, the specific interface will not be exported in DBus. 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 MMBroadbandModem 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 are multiple fully working plugins in the plugins/ directory that can be used as an example for writing new plugins. Writing new plugins is highly encouraged! The plugin 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! License. The ModemManager and mmcli binaries are both GPLv2+. The libmm-glib library is LGPLv2+.