Semyon Maryasin
225e66fea9
The qmi-proxy/mbim-proxy processes spawned by the daemon live in the
service's cgroup, so with the default KillMode=control-group systemd
sends SIGTERM to them at the same time as to the daemon on every unit
stop. The proxy exits immediately, tearing the control channel from
under the daemon while it is still disabling the modems:
<msg> caught signal, shutting down...
<msg> [modem0] state changed (connected -> disabling)
<msg> [modem0] port 'cdc-wdm0' no longer controllable, reprobing
<wrn> [/dev/cdc-wdm0] MBIM error: Device must be open to send commands
<wrn> shutdown failed: timeout waiting for sleep preparation to complete
The consequences of losing the proxy mid-shutdown:
- the modem disable/disconnect never reaches the device, so an MBIM
session with an active bearer is left open in the firmware (observed
to occasionally wedge the MBIM function of a Sierra EM7565 until a
firmware reset);
- the port teardown stalls waiting on the dead proxy until the
shutdown timeout, so stopping the unit always takes the full
MAX_SHUTDOWN_TIME_SECS instead of a second or two;
- the port invalidation triggers the device reprobe path in the middle
of the shutdown.
With KillMode=mixed only the daemon receives SIGTERM; the proxies
survive long enough for a clean disconnect and MBIM/QMI close, and
whatever remains in the cgroup afterwards (an idle, stateless proxy) is
killed when the unit finally stops.
Signed-off-by: Semyon Maryasin <simeon@maryasin.name>
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...).
Getting Started
ModemManager uses the meson build system. Meson is likely available as a package from your Linux distribution, but if not please refer to the Meson project for installation instructions. Once you have Meson installed you'll probably want to install libmbim and libqmi which most modems require.
After dependencies are installed you can build ModemManager with:
$ meson setup build --prefix=/usr --buildtype=release
$ ninja -C build
And after a successful build, install with:
$ sudo ninja -C build install
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+ (See COPYING). The libmm-glib library and the ModemManager API headers are LGPLv2+ (See COPYING.LIB).
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