Bug#877024: modemmanager should ask before messing with serial ports
Hey Ian,
On Thu, Oct 12, 2017 at 2:39 PM, Ian Jackson
<ijackson@chiark.greenend.org.uk> wrote:
> Aleksander Morgado writes ("Bug#877024: modemmanager should ask before messing with serial ports"):
>> This is part of the discussion we had in the MM mailing list for such
>> a solution:
>> https://lists.freedesktop.org/archives/modemmanager-devel/2017-September/005917.html
>
> Thanks, this looks constructive.
>
> Of the heuristics in that mail, most seem to me to be very sound
> justifications for thinking that the device is safe to probe.
>
> The one big exception is this:
>
> | * If vid is a known modem vendor (e.g. huawei, zte, sierra, u-blox,
> | telit....), it's a modem and we probe the tty.
>
> This is a hostage to the future, since of course we don't know what
> devices might be manufactured by a particular vendor in the many-years
> life of a Debian release.
>
Yes, this one is probably the weakest rule of all. Still not sure at
which point to apply the rule, though. E.g. should it be applied after
having applied all the previous rules (in that case it would be a very
safe rule, maybe totally unneeded) or should it be applied as an OR to
some other rule (e.g. driver is option/sierra/qcserial OR vendor is
huawei/zte..., in this case it would be a weaker rule). Will need to
decide this based on testing with real devices.
> I guess that if we in Debian don't like that particular heuristic it
> would be possible for us to disble just that one ?
>
> I don't understand this one:
>
> | * If kernel driver of the TTY is option/sierra/qcserial,
>
> but maybe it is OK.
>
The "option", "sierra" and "qcserial" drivers are all TTY kernel
drivers for modems. Most TTYs from USB modems would fall into one of
these. No non-modem device should bind to these drivers.
I'm planning to have a patch ready to play with in the following week,
will let you know.
--
Aleksander
https://aleksander.es
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