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      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 
     43 MODULE(MODULE_CLASS_MISC, sysctl, NULL);
     44 
     45 static int sysctl_example;
     46 
     47 static struct sysctllog *example_sysctl_log;
     48 
     49 static 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 
     71 static void
     72 sysctl_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 
    102 static int
    103 sysctl_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