modem probing takes too long

[Valmantas Palikša <walmis gmail com>]

I have ZTE MF633 and it has this "feature", opening or
closing /dev/ttyUSB1 blocks the program that is trying to open/close it
for about 5 seconds. This in turn slows down modem-manager's probing
speed. It takes about 60 seconds from plugging it in an entry appearing
in nm-applet's menu. I don't know whether this needs to be addressed in
kernel or MM, but it's quite annoying to wait for 1 minute for the modem
to be usable. Maybe probing ports in MM in parallel (threaded) makes
sense? Currently the PPP data ttyUSB port reports instantly, and I
imagine that a threaded solution would speed things considerably.