module(9)

NAME

module - structure describing a kernel module

DESCRIPTION

Each module in the kernel is described by a module_t struc

ture. The
structure contains the name of the device, a unique ID num

ber, 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_MODULE(9) macro registers the module with the

system.

When the module is loaded, the event handler function is

called with the
what argument set to MOD_LOAD.

On unload it is first called with 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 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 can

not be
revoked.

When the system is shutting down, what contains the value of
MOD_SHUTDOWN.

The module should return EOPNOTSUPP for unrecognized values

of 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,

};

MODULE_VERSION(foo, 1);
MODULE_DEPEND(foo, bar, 1, 3, 4);

DECLARE_MODULE(foo, mod_data, SI_SUB_EXEC, SI_ORDER_ANY);

SEE ALSO

DECLARE_MODULE(9), DEV_MODULE(9), DRIVER_MODULE(9), MOD

ULE_DEPEND(9),
MODULE_VERSION(9), SYSCALL_MODULE(9)

/usr/share/examples/kld

AUTHORS

This manual page was written by Alexander Langer

<alex@FreeBSD.org>.

BSD March 1, 2001

BSD