c07382a486
When a new USB device is hotplugged, e.g. a USB<->RS232 converter that exposes a single ttyUSB0, these udev events happen: add /devices/pci0000:00/0000:00:14.0/usb2/2-1 (usb/usb-device) add /devices/pci0000:00/0000:00:14.0/usb2/2-1/2-1:1.0 (usb/usb-interface) add /devices/pci0000:00/0000:00:14.0/usb2/2-1/2-1:1.0/ttyUSB0 (usb-serial) add /devices/pci0000:00/0000:00:14.0/usb2/2-1/2-1:1.0/ttyUSB0/tty/ttyUSB0 (tty) bind /devices/pci0000:00/0000:00:14.0/usb2/2-1/2-1:1.0/ttyUSB0 (usb-serial) bind /devices/pci0000:00/0000:00:14.0/usb2/2-1/2-1:1.0 (usb/usb-interface) bind /devices/pci0000:00/0000:00:14.0/usb2/2-1 (usb/usb-device) Our udev rules in MM only added tags in the 'add' events, and it looks like the only ones 'persistent' after this sequence are those of the last event happening on the specific path. This meant that all TTY subsystem rules (e.g. ID_MM_CANDIDATE) would be stored for later check (e.g. if ModemManager is started after these rules have been applied), which was ok. "udevadm info -p ..." would show these tags correctly always. But this also meant that the 'bind' udev event happening for the USB device didn't get any of our device-specific tags, and so we would be missing them (e.g. ID_MM_DEVICE_MANUAL_SCAN_ONLY) if MM is started after the last event has happened. "udevadm info -p ..." would not show these tags. Modify all our rules to also run at the 'bind' events. See, for context: https://github.com/systemd/systemd/issues/8221
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+.