Instantiating rmnet devices for data ports on QRTR-based modems

Eric Caruso ejcaruso at
Mon Oct 19 13:10:53 UTC 2020

On Mon, Oct 19, 2020 at 3:57 AM Aleksander Morgado
<aleksander at> wrote:
> Hey,
> > > >         I seem we have done for "QMI based on QTRT" in libqmi.
> > > >         For QUALCOMM's data services, there are lots of QMI library,
> > > > and libqmi used a more simply solution. (in fact, if just send QMI,
> > > > QTRT is also not a good idea)
> > >
> > > Why do you say QRTR is not a good idea? Isn't QMI over QRTR the only way to
> > > handle the communication in certain setups?
> > [carl.yin] 1. QRTR codes is much complex than direct send QMI message via QMI channel like /dev/cdc-wdm0
> >                 And it is not easy to find real hardware device for the QTRT node.
> >                 No matter the hardware interface between AP and Qualcomm modem is USB/PCIE/SMD,
> >                 (SMD is for QUALCOMM inter-AP, like MDM, APQ,MSM chipset.)
> >                 There always have QMI channel can be used to send QMI message.
> >                 If use these QMI channel, very few modifies is need apply to libqmi and MM
> I cannot comment on this, probably @Eric Caruso has a better point of view.

Right, we are working with a modem that does not have a real hardware
device in sysfs at all. It operates over a bus that is
sort-of-but-not-exactly PCIe and QRTR is the only mechanism by which
we can talk to it. I think the part where there is always another QMI
channel (USB/PCIe/SMD) should be true as long as you are using a
discrete module, otherwise.


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