If a user created a custom config file and we added new fields in a
newer version, `eg25-manager` will crash by assuming all config files
are complete and up-to-date.
Moreover, creating a custom config, even to change only one option,
required copying a complete default config file and then editing the
relevant field(s). This could lead to issues when upgrading, as default
values of fields unrelated to the user change could be modified and not
applied to the user config.
This patch addresses both these issues by:
* making sure at least one config file exists
* requiring only the "default" config file (the one under `/usr/share`)
to include all the required fields
* trying to use user config for each field, falling back to the default
config file if the field isn't present in the user config
* exiting with a meaningful error message in case the default config
file is missing a required field or section
That way, it will be possible to have a minimal user config file
containing only the field(s) needing a different value than the default
one, falling back to the values in the default config file.
Fixes#23
A temporary file is used to download the GNSS assistance data.
It's created and truncated at initialization, but not truncated
when a re-upload is necessary (when data expires).
This causes to corrupt the GNSS assistance data if the new downloaded
data is smaller than the previous download.
ModemManager Location service is only available after SIM unlock
and network registration.
Track service separately to avoid an assert error and crashes.
GNSS assistance data is uploaded when the service becomes available.
Automatically fetch the GNSS assistance data from the Web
to heavily reduce the time to acquire a GNSS lock by uploading
the assistance data to the modem.
This feature is optional and can be disabled in the configuration
as people may prefer to not download the assistance data from
the Quectel/Qualcomm servers.
Also configure the GNSS engine to optimize the performance
and power consumption.
