[Linux Device Drivers 3rd Notes] 1. Device driver introduction

Device drivers在linux kernel种起着特殊的作用，当hardware和internal programming interface需要通讯的时候，drivers就会在runtime被plug-in进来。

The role of a device driver is providing mechanism, not policy.

如何区分mechanism与policy? "What capabilities are to be provided" -> mechanism,  "How those capabilities can be used" -> policy

Kernel's role:

    1. Proces management - Creating and destroying processes / handling their connection to the outside world (input and output) / communication among different processes / control how processes ahre the CPU

    2. Memory management - Builds up a virtual addressing space for all processes / simple malloc and free pair to much more complex functionalities

    3. File systems - Build a structured filesystem on top of unstructured hardware

    4. Device control - Control all devices by device driver

    5. Networking - Delivering data packets across program and network interfaces / implement routing and address resolution issues.