692d076ba6
This commit introduces several improvements and changes in the way modes and capabilities are managed in QMI capable devices. It is organized into a single commit, as all changes in all 6 operations (load current capabilities, load supported capabilities, set current capabilities, load supported modes, load current modes, set current modes) are related one to the other (given that the same QMI commands are used for both capabilities and mode management). The primary change is related to which capabilities are reported as supported for a given device. In the previous implementation we allowed switching between every combination possible for GSM/UMTS+LTE, CDMA/EVDO+LTE or GSM/UMTS+CDMA/EVDO+LTE devices. E.g. we would allow "LTE only" and "GSM/UMTS only" capabilities for GSM/UMTS+LTE devices, even if they would both be managed in exactly the same way. That setup wasn't ideal, because it meant that switching to a "LTE only" configuration would require a power cycle, as capability switching requires a power cycle, even if no change was expected in the exposed DBus interfaces (which is why we require the power cycle). So, instead of allowing every possible capability combination, we use capability switching logic exclusively for configuring GSM/UMTS+CDMA/EVDO devices (regardless of whether it has LTE or not) to add or remove the GSM/UMTS and CDMA/EVDO capabilities. E.g. for a GSM/UMTS+CDMA/EVDO+LTE device we would allow 3 combinatios: "GSM/UMTS+LTE", "CDMA/EVDO+LTE" and "GSM/UMTS+CDMA/EVDO+LTE". The "GSM/UMTS+CDMA/EVDO+LTE" is a special case because for this one we allow switching to "LTE only" capabilities while we forbid switching to "4G only" mode. As the same commands are used for mode and capability switching, if we didn't have "LTE only" and we allowed "4G only" mode instead and rebooted the device, we would end up not being able to know which other capabilities (GSM/UMTS or CDMA/EVDO or both) were also enabled. Now that we have capability switching confined to a very subset of combinations, we can use the mode switching logic to e.g. allow "4G only" configurations in all non multimode devices, as well as masks of allowed modes with one being preferred, which we didn't allow before. In the previous implementation all mode switching logic was disabled for LTE capable QMI devices. In the new implementation, we use the "Acquisition Order Preference" TLV in NAS Set System Selection Preference to define the full list of mode preferences for all supported modes. We also no longer just assume that NAS Technology Preference is always available and NAS System Selection Preference only after NAS >= 1.1. This logic is flawed, instead we're going to probe for those features once when loading current capabilities, and we then just implement the capabilities/mode switching logic based on that.
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+.