pr2_arm_kinematics is a PR2 specific implementation of forward and inverse kinematics. To see examples of how to use this package, check out these <a href="http://www.ros.org/wiki/pr2_kinematics/Tutorials</a> tutorials <a href=".
The code API for the pr2_arm_kinematics package is in two forms: a KDL API that takes KDL structures as inputs and returns solutions as a KDL JntArray and a node API that takes a service call request as input and returns a service call response. The KDL solver API can be found here. The node API can be found here.