Hey all, > > When using the "strict" filter in ModemManager, we try to use > different heuristics to guess whether a device is a modem or not. > > One of the checks we do is looking at the exposed interfaces: if the > device exposes one or more ttyACM ports that report themselves as "AT > capable" (class=2/subclass=2/protocol=1), then we assume the device is > a modem device and we perform port probing. > > Well, it looks like several Arduino devices expose ttyACM ports and > advertise them as AT-capable even if they aren't. [1] > > Disabling the ttyACM AT-capable filter rule with the > "MM_FILTER_RULE_TTY_ACM_INTERFACE=0" environment variable makes the > Arduino device no longer probed because they're not accepted by any > other of the heuristics. [2] > > Should we remove the ttyACM AT-capable filter rule? If we do this and > there are modems out there that expose exclusively ttyACM ports (and > no NET port) then we would not probe them any more. I'm not sure I can > think of any modem that *only* exposes ttyACM ports, except for > "special" setups like a MC7455 running in a system that doesn't have > QMI or MBIM kernel drivers available. Still, this may be a usecase for > some people, don't know. > > Or should we keep a new short blacklist that would apply also in > "strict" filter mode? > > I'm tempted to write and maintain the new short blacklist, because I'd > also like to remove completely the old greylist/blacklists at some > point in the future (1.12?). What do you all think? > > [1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=930264 > [2] https://gitlab.freedesktop.org/mobile-broadband/ModemManager/issues/127 >
This is the approach I'm going to suggest to avoid this issue, comments welcome: https://gitlab.freedesktop.org/mobile-broadband/ModemManager/merge_requests/143 With the change to ignore ttyACM ports with protocol=1, we would be ignoring all Arduino devices that are wrongly claiming AT protocol support. Only this protocol=1 value is being ignored because that is the value that was used as default in Arduino. What do you all think? -- Aleksander https://aleksander.es _______________________________________________ ModemManager-devel mailing list ModemManager-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/modemmanager-devel
