/*      $NetBSD: sysctl.c,v 1.2 2021/03/23 13:19:09 simonb Exp $        */

/*-
* Copyright (c) 2018 The NetBSD Foundation, Inc.
* All rights reserved.
*
* 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
*/

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: sysctl.c,v 1.2 2021/03/23 13:19:09 simonb Exp $");

#include <sys/param.h>
#include <sys/module.h>
#include <sys/sysctl.h>

/*
* Check if sysctl -A contains an entry
*    example_subroot1.sysctl_example=0
* to test this module
*
*/

MODULE(MODULE_CLASS_MISC, sysctl, NULL);

static int sysctl_example;

static struct sysctllog *example_sysctl_log;

static void sysctl_example_setup(struct sysctllog **);


/*
* sysctl_example_setup :
*    It first creates a subtree by adding a node to the tree.
*    This node is named as example_subroot1.
*
*    It then creates a node in subtree for the example variable which
*    is an integer and is defined in this file itself.
*
*                      ROOT
*                        |
*                        -------
*                              |
*                       examples_subroot1
*                              |
*                              |
*                        sysctl_example (INT)
*
*/

static void
sysctl_example_setup(struct sysctllog **clog)
{
       const struct sysctlnode *rnode;

       sysctl_createv(clog, 0, NULL, &rnode,
                       CTLFLAG_PERMANENT,
                       CTLTYPE_NODE, "example_subroot1",
                       NULL,
                       NULL, 0,
                       NULL, 0,
                       CTL_CREATE, CTL_EOL);

       sysctl_createv(clog, 0, &rnode, NULL,
                      CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                      CTLTYPE_INT, "sysctl_example",
                      SYSCTL_DESCR("An example for sysctl_example"),
                      NULL, 0,
                      &sysctl_example, 0,
                      CTL_CREATE, CTL_EOL);
}

/*
*  The sysctl_example modcmd has two functions.
*  1. Call the sysctl_example_setup function to create a sysctl
*     handle when the module is loaded in the kernel.
*  2. Remove the sysctl entry from the kernel once the module
*     is unloaded.
*/


static int
sysctl_modcmd(modcmd_t cmd, void *arg)
{
       switch(cmd) {
       case MODULE_CMD_INIT:
               printf("sysctl module inserted\n");
               sysctl_example_setup(&example_sysctl_log);
               break;
       case MODULE_CMD_FINI:
               printf("sysctl module unloaded\n");
               sysctl_teardown(&example_sysctl_log);
               break;
       default:
               return ENOTTY;
       }
       return 0;
}