A skeleton kernel module suitable for creating new such modules.

share/examples/modules/Makefile

@@ -0,0 +1,6 @@
+.PATH: ${SRCTOP}/sys/skel
+
+KMOD=	skel
+SRCS=	skel.c
+
+.include <bsd.kmod.mk>

share/examples/modules/skel.c

@@ -0,0 +1,87 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2023 George V. Neville-Neil
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ */
+
+/*
+ * SKEL Loadable Kernel Module for the FreeBSD Operating System
+ * 
+ * The SKEL module is meant to act as a skeleton for creating new
+ * kernel modules.
+ *
+ * This module can be loaded and unloaded from * FreeBSD and is for
+ * use in teaching as well.
+ *
+ */
+
+#include <sys/cdefs.h>
+#include <sys/param.h>
+#include <sys/kernel.h>
+#include <sys/systm.h>
+#include <sys/module.h>
+
+/*
+ * Every module can hav ea module specific piece of code that is
+ * executed whenever the module is loaded or unloaded.  The following
+ * is a trivial example that prints a message on the console whenever
+ * the module is loaded or unloaded.
+ */
+
+static int
+skel_mod_event(module_t mod, int type, void *data)
+{
+
+	switch (type) {
+	case MOD_LOAD:
+		printf("SKEL module loading.\n");
+		return (0);
+	case MOD_UNLOAD:
+		printf("SKEL module unloadin.\n");
+		return (0);
+	}
+	return (EOPNOTSUPP);
+}
+
+/*
+ * Modules can have associated data and the module data also contains
+ * an entry for the function called by the kernel on load and unload.
+ */
+
+static moduledata_t skel_mod = {
+	"skel",
+	skel_mod_event,
+	NULL,
+};
+
+/*
+ * Each module is declared with its name and module data.  The
+ * ordering arguments at the end put this module into the device
+ * driver class, which is sufficient for our needs.  The complete list
+ * of modules types and ording can be found in sys/kernel.h
+ */
+
+DECLARE_MODULE(skel, skel_mod, SI_SUB_DRIVERS, SI_ORDER_MIDDLE);
+