1/*	$NetBSD: sysctl.c,v 1.2 2021/03/23 13:19:09 simonb Exp $	*/
2
3/*-
4 * Copyright (c) 2018 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
17 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
18 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
19 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
20 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
21 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
22 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
23 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
24 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
25 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
26 * POSSIBILITY OF SUCH DAMAGE.
27 */
28
29#include <sys/cdefs.h>
30__KERNEL_RCSID(0, "$NetBSD: sysctl.c,v 1.2 2021/03/23 13:19:09 simonb Exp $");
31
32#include <sys/param.h>
33#include <sys/module.h>
34#include <sys/sysctl.h>
35
36/*
37 * Check if sysctl -A contains an entry
38 *    example_subroot1.sysctl_example=0
39 * to test this module
40 *
41 */
42
43MODULE(MODULE_CLASS_MISC, sysctl, NULL);
44
45static int sysctl_example;
46
47static struct sysctllog *example_sysctl_log;
48
49static void sysctl_example_setup(struct sysctllog **);
50
51
52/*
53 * sysctl_example_setup :
54 *    It first creates a subtree by adding a node to the tree.
55 *    This node is named as example_subroot1.
56 *
57 *    It then creates a node in subtree for the example variable which
58 *    is an integer and is defined in this file itself.
59 *
60 *                      ROOT
61 *                        |
62 *                        -------
63 *                              |
64 *                       examples_subroot1
65 *                              |
66 *                              |
67 *                        sysctl_example (INT)
68 *
69 */
70
71static void
72sysctl_example_setup(struct sysctllog **clog)
73{
74	const struct sysctlnode *rnode;
75
76	sysctl_createv(clog, 0, NULL, &rnode,
77			CTLFLAG_PERMANENT,
78			CTLTYPE_NODE, "example_subroot1",
79			NULL,
80			NULL, 0,
81			NULL, 0,
82			CTL_CREATE, CTL_EOL);
83
84	sysctl_createv(clog, 0, &rnode, NULL,
85		       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
86		       CTLTYPE_INT, "sysctl_example",
87		       SYSCTL_DESCR("An example for sysctl_example"),
88		       NULL, 0,
89		       &sysctl_example, 0,
90		       CTL_CREATE, CTL_EOL);
91}
92
93/*
94 *  The sysctl_example modcmd has two functions.
95 *  1. Call the sysctl_example_setup function to create a sysctl
96 *     handle when the module is loaded in the kernel.
97 *  2. Remove the sysctl entry from the kernel once the module
98 *     is unloaded.
99 */
100
101
102static int
103sysctl_modcmd(modcmd_t cmd, void *arg)
104{
105	switch(cmd) {
106	case MODULE_CMD_INIT:
107		printf("sysctl module inserted\n");
108		sysctl_example_setup(&example_sysctl_log);
109		break;
110	case MODULE_CMD_FINI:
111		printf("sysctl module unloaded\n");
112		sysctl_teardown(&example_sysctl_log);
113		break;
114	default:
115		return ENOTTY;
116	}
117	return 0;
118}
119