This is intended to be a guide to the inner workings of the N900 GPS subsystem. It will provide info people who want to talk to the GPS hardware can use as well as info people who want to totally replace the GPS subsystem (e.g. for Neo900) can use. And people who just want to talk to it or understand how it works.

Part 1 will give an overview of the N900 GPS subsystem
Part 2 will talk about how to talk to the GPS hardware at the low level via isi/phonet messages
Part 3 will describe the gconf, dbus and other interfaces involved in the various components.

On the N900, the GPS hardware is connected via the cellular modem. The main processor talks to the GPS via isi/phonet messages. The GPS subsystem is made up of 4 components. liblas is the low level library used to talk to the GPS hardware (it sends isi/phonet messages to the cellular modem via libisi). location-daemon is the daemon that handles the GPS position stuff. location-proxy is the daemon that handles supl and AGPS data and passes it to the cellular modem. liblocation is the library that other apps use to talk to the GPS subsystem.