.. _diver_implement:


Device Driver Implementation
==============================

Device Independent Function Call
-----------------------------------

.. figure:: device_indep_function.png
   :align: center

   System calls use a table to use and execute the correct driver code.

Driver--Kernel Interface
----------------------------

* Drivers are distinct from the main part of the kernel.

* The kernel makes calls to specific functions, drivers implement them.

* Drivers use kernel functions for:

    - Device allocation

    - Resource (e.g., memory) allocation

    - Scheduling

    - etc. (varies from OS to OS)

Reconfigurable Device Drivers
------------------------------

.. figure:: reconfig_driver.png
   :align: center

   Modern systems can be reconfigured with tables holding pointers to
   functions.  This allows drivers to be added without recompiling the
   Operating System kernel.