Preventing MM from probing specific serial ports on supported modems

[Bjørn Mork]

Bjørn Mork <bjorn at mork.no> writes:

> I'm sure there must be some way to do this, but I'm unable to figure out
> how.  I want MM to completely ignore the GPS NMEA port on the MC7455.  I
> want that port to be handled by gpsd.  And having two daemons touching
> the same port does feel a bit yucky.  Besides, MM doesn't really deal
> all that well with NMEA and sometimes crashes while running the AT
> probe:

Still wondering about how to configure this.  MM doesn't crash when
probing the GPS port anymore, but now I have a modem firmware which
does....

I have the GPS function confgured to autostart on '$GPS_START', to save
some power when it's not in use (this was the Lenovo default setting,
BTW).  And the GPS port works fine if I ensure that '$GPS_START' is the
first thing it sees.  But if ModemManager is running, then there will be
some failing AT commands sent first during port probing. Nothing bad
happens as long as I don't use the GPS at all, but sending '$GPS_START'
after the MM probing causes the firmware to always reset.

This is a Lenovo EM7455 with firmware version SWI9X30C_02.20.03.00.

The issue is of course a firmware bug.  But anyway: It would be nice to
be able to flag this port as "do not touch" for MM.  The AT probing is a
waste of time in the best case.  And the firmware issue is an example of
unnecessary problems due to the unexpeced probes.

Note that it is possible to have a very generic GPS port rule for all
Sierra modems, since they always use the same USB interface number.  So
if there only was a way to blacklist individual USB interfaces on
otherwise managed modems...



Bjørn