qmi_wwan add_mux/del_mux

[Aleksander Morgado]

Hey again,

> Say I create a new muxed interface for mux id 5:
>   echo 5 > /sys/class/net/wwan0/qmi/add_mux
> A new qmimux0 interface is created.
>
> Is there any way to know which mux id was used to create the qmimux0
> looking just at sysfs or some other way? In other words, how would I
> know what the mux id is for a given qmimuxN interface that may not
> have been created by me?
>
> Also, say that I have 2 different programs creating this kind of
> interfaces, and both use the qmi/add_mux attribute. If they both run
> at the same time (asking for different mux ids), and two interfaces
> qmimux0 and qmimux1 are created, how can each program know which was
> the interface corresponding to the mux id they requested?
>
> Not sure I'm missing something, but I didn't find a way to do this
> kind of matchings. If the virtual qmimux interface exposed a sysfs
> attribute specifying which is the mux id they correspond to, the
> matching would be much easier. Would that be possible?
>
> For context, I'm trying to work on adding support for this interface
> in libqmi, with the new qmi_device_add_link() interface that is right
> now only available when using rmnet with netlink.
>

In the context of multiplexing QMUX data sessions, Stephan also
suggested we revive this old patch that never got a v2 in the LKML:
https://lore.kernel.org/netdev/1530066614-24995-1-git-send-email-subashab@codeaurora.org/

Adding support to use rmnet on top of qmi_wwan seems like a good idea,
and we would be able to use the implementation we already have for
e.g. IPA, e.g.:
https://gitlab.freedesktop.org/mobile-broadband/libqmi/-/merge_requests/184#note_715900

What do you all think?
-- 
Aleksander
https://aleksander.es