30ea91e353
The AT control TTYs in the u-blox modems may take some time to be usable. In order to handle this issue, we configured some longer timeouts during AT probing, but that may not be always enough. The u-blox TTYs will report readiness via a "+AT: READY" URC, which we can use during custom initialization to decide right away that the port is AT. We use up to 20s as that is close to the worst case seen during experimentation, happening after the module undergoes a full NVM reset. If the timeout is reached without receiving the URC, we still run standard AT probing afterwards. This new logic just tries to make it sure we don't do any probing before the module is ready to accept it. If the module hasn't been hotplugged (i.e. it was already there when ModemManager started) we do a quick first AT probing and if that fails we run the "+AT: READY" URC wait as if it was hotplugged.
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+.