Why write a resource manager?

Here are a few reasons why you'd want to write a resource manager:

• The client API is POSIX.

  The API for communicating with the resource manager is, for the most part, POSIX. All C programmers are familiar with the open(), read(), and write() functions. Training costs are minimized, and so is the need to document the interface to your server.

• You can reduce the number of interface types.

  If you have many server processes, writing each server as a resource manager keeps the number of different interfaces that clients need to use to a minimum.

  An example of this is if you have a team of programmers building your overall application, and each programmer is writing one or more servers for that application. These programmers may work directly for your company, or they may belong to partner companies who are developing add-on hardware for your modular platform.

  If the servers are resource managers, then the interface to all of those servers is the POSIX functions: open(), read(), write(), and whatever else makes sense. For control-type messages that don't fit into a read/write model, there's devctl() (although devctl() isn't POSIX).

• Command-line utilities can communicate with resource managers.

  Since the API for communicating with a resource manager is the POSIX set of functions, and since standard POSIX utilities use this API, the utilities can be used for communicating with the resource managers.