Debian discussion to disable automatic TTY probing

[Dan Williams]

On Thu, 2017-09-28 at 17:58 +0200, Aleksander Morgado wrote:
> Hey!
> 
> FYI
> 
> Got told today that Debian is discussing whether to disable automatic
> probing of TTY devices in MM, some links:
> 
> https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=877024
> https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=683839
> 
> This is the ModemManager bug report about this issue, for reference:
> https://bugs.freedesktop.org/show_bug.cgi?id=85007

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
discussing.

Dan