©2006 Eridani Star System.
All rights reserved.
DISCLAIMER: This requires a kernel patch for kernels earlier than 2.4.21rc1. Please exercise caution.

Known to work with: V66, T280, T720i, V5xx, V3 RAZR, Nextel i95cl (and possibly others) which can use a USB data lead.

You only need to download this patch if you use a kernel older than 2.4.21rc1. Tested with kernel 2.4.19 and reported to work with 2.4.20. This patch is included in the standard 2.4.21 release and later, and current 2.6 kernels.

If required, apply the patch to your kernel source, and recompile, ensuring that you include the "USB Modem (CDC ACM)" driver in your kernel or as a module.

Under devfs your modem is now /dev/usb/acm/0, udev will call it /dev/ttyACM0 - or if you don't use either devfs or udev, create the device node with:

mknod /dev/ttyACM0 c 166 0

This port can be used like any other modem device to connect to your ISP, minicom and pppd will work with it.

Niggles: If you're using a modular USB setup, load the acm module before plugging your phone in - for some reason if you load the module after plugging the phone in it doesn't work. To make matters worse, if you unplug the phone, you may need to power cycle it if the syslog indicates that it doesn't like to be assigned a new device ID, though this seems to depend on chipset. This niggle occurs on my onboard USB1.1 (UHCI) port on my Vaio but doesn't occur on my Belkin USB2 (OHCI/EHCI) PCMCIA card. Go figure...
Using a Motorola GSM cellular phone with Linux and USB