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.Dd February 13, 2018
.Dt DECLARE_MODULE 9
.Os
.Sh NAME
.Nm DECLARE_MODULE
.Nd kernel module declaration macro
.Sh SYNOPSIS
.In sys/param.h
.In sys/kernel.h
.In sys/module.h
.Fn DECLARE_MODULE "name" "moduledata_t data" "sub" "order"
.Fn DECLARE_MODULE_TIED "name" "moduledata_t data" "sub" "order"
.Sh DESCRIPTION
The
.Fn DECLARE_MODULE
macro declares a generic kernel module.
It is used to register the module with the system, using the
.Fn SYSINIT
macro.
.Fn DECLARE_MODULE
is usually used within other macros, such as
.Xr DRIVER_MODULE 9 ,
.Xr DEV_MODULE 9
and
.Xr SYSCALL_MODULE 9 .
Of course, it can also be called directly, for example in
order to implement dynamic sysctls.
.Pp
A module declared with
.Fn DECLARE_MODULE_TIED
will load only if the running kernel version
(as specified by
.Dv __FreeBSD_version )
is identical to that on which it was built.
This declaration should be used by modules which depend on interfaces beyond
the stable kernel KBI (such as ABI emulators or hypervisors that rely on
internal kernel structures).
.Fn DECLARE_MODULE
will behave like
.Fn DECLARE_MODULE_TIED
when compiled with modules built with the kernel.
This allows locks and other synchronization primitives
to be inlined safely.
.Pp
The arguments are:
.Bl -tag -width indent
.It Fa name
The module name, which will be used in the
.Fn SYSINIT
call to identify the module.
.It Fa data
A
.Vt moduledata_t
structure, which contains two main items, the official name of the
module name, which will be used in the
.Vt module_t
structure and a pointer to the event handler function of type
.Vt modeventhand_t .
.It Fa sub
An argument directed to the
.Fn SYSINIT
macro.
Valid values for this are contained in the
.Vt sysinit_sub_id
enumeration
(see
.In sys/kernel.h )
and specify the type of system startup interfaces.
The
.Xr DRIVER_MODULE 9
macro uses a value of
.Dv SI_SUB_DRIVERS
here for example, since these modules contain a driver for a device.
For kernel modules that are loaded at runtime, a value of
.Dv SI_SUB_EXEC
is common.
.It Fa order
An argument for
.Fn SYSINIT .
It represents the KLDs order of initialization within the subsystem.
Valid values are defined in the
.Vt sysinit_elem_order
enumeration
.Pq In sys/kernel.h .
.El
.Sh SEE ALSO
.Xr DEV_MODULE 9 ,
.Xr DRIVER_MODULE 9 ,
.Xr module 9 ,
.Xr SYSCALL_MODULE 9
.Pp
.Pa /usr/include/sys/kernel.h ,
.Pa /usr/share/examples/kld
.Sh AUTHORS
.An -nosplit
This manual page was written by
.An Alexander Langer Aq Mt alex@FreeBSD.org ,
inspired by the KLD Facility Programming Tutorial by
.An Andrew Reiter Aq Mt arr@watson.org .