For some reason, the ModemManager build tends to freeze when built
with QEMU user emulation for arm*. Changing the build to use a single
thread only (-j1) avoids that, although the build is slower of course.
Also limit building to "armhf armv7 aarch64" since the forks are not
needed on any other architectures, to reduce build times a bit. The
other architectures can just use the upstream packages from Alpine.
Most older Qualcomm SoCs (e.g. MSM8916, MSM8974, ...) communicate
with the modem through shared memory. On mainline kernels these
shared memory channels are exposed through the RPMSG subsystem.
This is different from communication through USB or serial interfaces
that are currently supported by ModemManager.
This commit forks the "modemmanager" package from Alpine and adds
a patch that allows ModemManager to talk to modems through the RPMSG
subsystem.
Working functionality: Calls, SMS, Mobile Data
The same patch has also been submitted upstream:
https://gitlab.freedesktop.org/mobile-broadband/ModemManager/-/merge_requests/363
