udev, HAL, DBUS

19 Dec 2008

A good post from Glen Turner on SLUG about udev, HAL, DBUS (in the context of GSM modems):

- you insert the device
 - UDEV tells HAL that it has been inserted
 - HAL looks up a XML-based "information" file. These are where the
   rubber hits the road.  The system files are in
     /usr/share/hal/fdi/
   and any files you may write go into
     /etc/hal/fdi/
 - HAL determines from the USB vendor/model codes it was handed
   that you've got a GSM modem. The policy files contain related
   details like which USB Serial port to use for PPP, what dialing
   algorithm to use, etc.
 - HAL pumps these details to NetworkManager, probably via DBUS
 - NetworkManager daemon chats with the NetworkManager applet to
   grab other data, such as PIN numbers
 - NetworkManager kicks off PPP using the combined information
   from HAL and the NM applet.