Debian discussion to disable automatic TTY probing

Dan Williams dcbw at
Thu Sep 28 16:54:07 UTC 2017

On Thu, 2017-09-28 at 17:58 +0200, Aleksander Morgado wrote:
> Hey!
> Got told today that Debian is discussing whether to disable automatic
> probing of TTY devices in MM, some links:
> This is the ModemManager bug report about this issue, for reference:

The problem cases here are:

1) generic USB/serial converters
- we can't easily handle this one
2) cdc-acm devices
- we could theoretically only auto-probe ttys that specify
class=2/subclass=2/protocol=1 (Communications/Abstract/AT-commands),
but I'm sure there are some devices that don't adhere to the specs well
3) modems that haven't been added to kernel drivers yet
- can't do much here, and there are probably a lot of these especially
with older kernels
4) platform devices
- we already graylist these

For almost all others you can key off the kernel driver type.  So I
guess if Debian wants greylist everything, but then they'll need to
come up with a "probe my modem!" tool with a UI that doesn't suck.  And
there's the problem...

But MM could do better at whitelisting certain classes of device to
help out with the greylist-by-default strategy they are probably


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