DESCRIPTION
Each module in the kernel is described by a Vt module_t structure. The structure contains the name of the device, a unique ID number, a pointer to an event handler function and to an argument, which is given to the event handler, as well as some kernel internal data.The DECLARE_MODULE9 macro registers the module with the system.
When the module is loaded, the event handler function is called with the Fa what argument set to MOD_LOAD
On unload it is first called with Fa what set to MOD_QUIESCE If the unload was not forced, a non-zero return will prevent the unload from happening.
If the unload continues Fa what is set to MOD_UNLOAD If the module returns non-zero to this, the unload will not happen.
The difference between MOD_QUIESCE and MOD_UNLOAD is that the module should fail MOD_QUIESCE if it is currently in use, whereas MOD_UNLOAD should only fail if it is impossible to unload the module, for instance because there are memory references to the module which cannot be revoked.
When the system is shutting down, Fa what contains the value of MOD_SHUTDOWN
The module should return Er EOPNOTSUPP for unsupported and unrecognized values of Fa what .
EXAMPLES
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/module.h>
static int foo_handler(module_t mod, int /*modeventtype_t*/ what,
void *arg);
static moduledata_t mod_data= {
"foo",
foo_handler,
NULL
};
MODULE_VERSION(foo, 1);
MODULE_DEPEND(foo, bar, 1, 3, 4);
DECLARE_MODULE(foo, mod_data, SI_SUB_EXEC, SI_ORDER_ANY);