[Buildroot] [PATCH] package/modem-manager: use libqmi and libmbim if they are selected

[Aleksander Morgado]

Hey Carlos,

>
> If we have a cnfiguration like this
>
>     BR2_PACKAGE_MODEM_MANAGER=y
>     # BR2_PACKAGE_MODEM_MANAGER_LIBMBIM is not set
>     BR2_PACKAGE_MODEM_MANAGER_LIBQMI=y
>     [...]
>     BR2_PACKAGE_LIBMBIM=y
>
> then libqmi is configured with --enable-mbim-qmux and requires libmbim
> so ModemManager must be configured --with-mbim otherwise it fails to
> link due to missing libmbim symbols required by libqmi:
>
>     qmi-endpoint-mbim.c:(.text+0x158): undefined reference to `mbim_device_close_finish'
>

Wouldn't this Libs.private fix in libqmi solve this specific build
problem? See http://lists.busybox.net/pipermail/buildroot/2019-October/264787.html

> Prevent this kind of error by using a simpler approach:
>
> - Always enable MBIM support if libmbim is selected
> - Drop BR2_PACKAGE_MODEM_MANAGER_LIBMBIM and add a legacy option that
>   selects BR2_PACKAGE_LIBMBIM
> - Always enable QMI support if libqmi is selected
> - Drop BR2_PACKAGE_MODEM_MANAGER_LIBQMI and add a legacy option that
>   selects BR2_PACKAGE_LIBQMI
> - Update the help text explaining how to enable MBIM and QMI
>

It is true that the current setup may lead to a strange configuration
where ModemManager may be built with only QMI support and no explicit
MBIM support while at the same time libqmi is built with MBIM support.
That would not be any problem per se, it would just be weird.

I'm not totally sure how these settings are usually preferred in
buildroot, truth be told. Maybe someone with more experience in
buildroot itself could suggest how to best handle this? Is it better
to have a setting in the ModemManager package to enable/disable
features explicitly? Or is it better to implicitly enable/disable
those features based on whether some other packages are also included
in the build? I guess the question would be whether we want to have a
non-QMI non-MBIM capable ModemManager installed at the same time as
libqmi+qmicli/libmbim+mbimcli. I have absolutely no idea whether this
is a real usecase for anyone or not, truth be told. If it is (or may
be) a real usecase, then I don't think this patch should go in.

-- 
Aleksander
https://aleksander.es