681d5d29d5
Recent Linux kernel versions have introduced a generic WWAN subsystem
that provides various char devices for QMI, AT etc, similar to the
subsystem-specific char devices for USB or RPMSG.
The RPMSG char device for Qualcomm SoCs (e.g. MSM8916/MSM8974)
are particularly complicated to work with because they need to be
explicitly created from userspace with rpmsgexport and don't show up
automatically.
However, it turns out it's fairly simple to wrap the RPMSG subsystem
in a simple driver for the WWAN subsystem. This has several advantages:
- We can drop support for the special RPMSG char devices entirely
at some point.
- The WWAN char devices show up automatically, without having to export
them explicitly, making ModemManager work out of the box on these devices.
For now, just support using the WWAN subsystem alternatively for the
qcom-soc plugin. Later we can consider dropping the old RPMSG code.
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 provide 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+. Code of Conduct. Please note that this project is released with a Contributor Code of Conduct. By participating in this project you agree to abide by its terms, which you can find in the following link: https://www.freedesktop.org/wiki/CodeOfConduct CoC issues may be raised to the project maintainers at the following address: modemmanager-devel-owner@lists.freedesktop.org