1.  What is a module?

A module is a collection of code which can be dynamicly linked into the
kernel.  Modules can contain things such as device drivers, system calls,
and file system types [system calls are actually nolonger permitted].


2.  How do I create a module?

A module consists of a normal .o file.  If you have multiple source
files, combine them into a single .o file using "ld -r".


3.  How does the kernel know to use my module?

Your code must contain a routine named "init_module" and a routine named
"cleanup_module".  These routines are defined as:

	"C" int init_module(void);
	"C" void cleanup_module(void);

"Init_module" will be called when the module is loaded.  It should return
zero on success and -1 on failure.  "Cleanup_module" will be called before
the module is deleted.  It should undo the operations performed by
"init_module".  For example, if a module defines a special device type
"init_module" should register the device major number and and
"cleanup_module" should remove it.


4.  Show me a simple example!

See drv_hello.c in this directory. Note the use count checking macros,
these prevent the module being freed while it is still running!
Also note for the module to be installed it must contain a string
kernel_version[] that matches the release of the current kernel (i.e.
matches uname -r).


5.  How do I load and unload modules?

"insmod object_file" will install a module into the kernel.  The name
of the module consists of the name of the object file with the .o and
any directory names removed.

"lsmod" will produce a list of modules currently in the kernel,
including the module name and size in pages.

"rmmod name" will remove a module.  The argument should be the module
name, not the object file name.

[Written by Jon Tombs or Bas Larhooven?]