Re: RS232 GSM Modem

[toabctl <toabctl googlemail com>]

2010/4/28 Dan Williams <dcbw redhat com>

On Wed, 2010-04-28 at 09:37 +0200, toabctl wrote:
> 1) How does network-manager detect that the modem is connected? Or how
> can i tell networkmanager on which port the modem is attached? I use a
> rs232<->usb adapter so the port is /dev/ttyUSB0 .

ModemManager uses udev for device detection.  It listens for udev events
(which you can also listen for with udevmonitor) and when it receives a
notification of a new serial port, it will inspect that port and attempt
to probe it.  

How does ModemManager probe the port? I want to use modem manager also with a rs232 device and there are no uevents because rs232 has no hotplug. but i could emit a uevent "by hand".

The information about the device (  /dev/ttyS1 ):

# udevadm info --query=all -n /dev/ttyS1
P: /devices/platform/atmel_usart.1/tty/ttyS1
N: ttyS1
S: char/4:65
E: UDEV_LOG=3
E: DEVPATH=/devices/platform/atmel_usart.1/tty/ttyS1
E: MAJOR=4
E: MINOR=65
E: DEVNAME=/dev/ttyS1
E: SUBSYSTEM=tty
E: DEVLINKS=/dev/char/4:65

# udevadm info --query=all -n /dev/ttyS1 --attribute-walk
...
looking at device '/devices/platform/atmel_usart.1/tty/ttyS1':
    KERNEL=="ttyS1"
    SUBSYSTEM=="tty"
    DRIVER==""

  looking at parent device '/devices/platform/atmel_usart.1':
    KERNELS=="atmel_usart.1"
    SUBSYSTEMS=="platform"
    DRIVERS=="atmel_usart"
    ATTRS{modalias}=="platform:atmel_usart"

  looking at parent device '/devices/platform':
    KERNELS=="platform"
    SUBSYSTEMS==""
    DRIVERS==""


How can i use this port with ModemManager? The modem is connected and AT-Commands works.
 

There are a number of requirements of the port though; it
verifies that the kernel has assigned a driver name to the port or one
of the port's parents, and it attempts to grab the port's physical
device.  Given that it's USB, it *should* work.  But if it doesn't, and
you have a chance to grab the ModemManager source [1], there's a tool
called 'lsudev' in the test/ directory that can give us an idea of the
udev-provided information of the device.

i guess 'lsudev' does the same as my 2 commands with 'udevadm', right? or does 'lsudev' something more special?
 

> 2) How does the connection-config looks like?

ModemManager is just a tool to control the modem, it doesn't store any
configuration about it.  The configuration is provided by a program that
tells ModemManager what to do.  There are a few ways to do that;
NetworkManager provides a general modem control solution, but you can
also write your own app that uses D-Bus to tell ModemManager what to do
with the modem.  See test/mm-test.py for a short example of how to use
python and D-Bus to make MM connect the modem and get information out of
it.

ah. that's great. i need to control the modem over a web-interface so no nm-applet available.


Cheers,

Tom