USB 3G modem changes

[Martin Husemann <martin%duskware.de@localhost>]

Folks,

I have commited some changes to the u3g driver where I'm not sure wether
they have any impact on previously working setups - please send-pr if you
find a regression.

There are basically two different variants of USB 3G modems: some just attach
as 3G modems and offer ucom devices. For this variants the current changes
do not change a lot: previously you might have got

  u3g0 at ....
  ucom0 at u3g0...
  ucom1 at u3g0...
  ucom2 at u3g0...
  ucom3 at u3g0...

and the latter two being unusable. Now you will get:

  u3g0 at ...
  ucom0 at u3g0...
  u3g1 at ...
  ucom1 at u3g1...

so no practical change in your setup, just slightly different attach messages.

The other variant of 3G modems initially comes as a umass device. You will
notice this by the u3g driver attaching, resetting the device and after a
few seconds u3g detaching and then reataching again.

There were systematic bugs in the code for the reinit, so this only worked
on Novatel cards.

Now in the new world order, this devices attach to the u3ginit driver, which
will reset them, detach, and next the devices will attach multiple drivers:

u3g0 at ....
ucom0 at ...
u3g1 at ...
ucom1 at ...
umass0 at ...
scsibus0 at umass0 ...

This allows you to access the emulated CD at umass which carries the windows
drivers (pretty much useless), but also on some devices allows access to
additional microSD cards appearing as sd0 drive.

If you have a device of the "umass-initially" kind and build your custom
kernel, you will have to add the u3ginit driver to your kernel config.

Martin