NetBSDカーネルモジュールでsysctlを実装するサンプルです。

netbsd_sysctl_sample.c

/*	$NetBSD: hello.c,v 1.1 2015/05/13 07:07:36 pgoyette Exp $	*/

/*-
 * Copyright (c) 2015 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: hello.c,v 1.1 2015/05/13 07:07:36 pgoyette Exp $");

#include <sys/param.h>
#include <sys/fcntl.h>
#include <sys/conf.h>
#include <sys/condvar.h>
#include <sys/device.h>
#include <sys/ioctl.h>
#include <sys/kmem.h>
#include <sys/lock.h>
#include <sys/module.h>
#include <sys/mutex.h>
#include <sys/namei.h>
#include <sys/queue.h>
#include <sys/sysctl.h>
#include <sys/vnode.h>
#include <sys/cpu.h>

struct hello_softc {
	device_t                 sc_dev;

	kmutex_t                 sc_lock;
	kcondvar_t               sc_inuse_cv;
	bool                     sc_inuse;

	/* Locking access to state queues */
	kmutex_t                 sc_state_lock;
	kcondvar_t               sc_state_cv;
	bool                     sc_state;

	struct sysctllog        *sc_log;
};

extern struct cfdriver hello_cd;

static device_t sc_self;
static int      hello_max_instr;

static int hello_match(device_t, cfdata_t, void *);
static void hello_attach(device_t, device_t, void *);
static int hello_detach(device_t, int);

CFATTACH_DECL_NEW(hello, sizeof(struct hello_softc),
	hello_match, hello_attach, hello_detach, NULL);

const struct cdevsw hello_cdevsw = {
	.d_open = noopen,
	.d_close = noclose,
	.d_read = noread,
	.d_write = nowrite,
	.d_ioctl = noioctl,
	.d_stop = nostop,
	.d_tty = notty,
	.d_poll = nopoll,
	.d_mmap = nommap,
	.d_kqfilter = nokqfilter,
	.d_discard = nodiscard,
	.d_flag = D_OTHER | D_MPSAFE
};

MODULE(MODULE_CLASS_MISC, hello, NULL);


#ifdef _MODULE
static const struct cfiattrdata hellobus_iattrdata = {
	"hellobus", 0, { { NULL, NULL, 0 },}
};
static const struct cfiattrdata *const hello_attrs[] = {
	&hellobus_iattrdata, NULL
};
CFDRIVER_DECL(hello, DV_DULL, hello_attrs);
extern struct cfattach hello_ca;
static int helloloc[] = {
	-1,
	-1,
	-1
};
static struct cfdata hello_cfdata[] = {
	{
		.cf_name = "hello",
		.cf_atname = "hello",
		.cf_unit = 0,
		.cf_fstate = FSTATE_STAR,
		.cf_loc = helloloc,
		.cf_flags = 0,
		.cf_pspec = NULL,
	},
	{ NULL, NULL, 0, FSTATE_NOTFOUND, NULL, 0, NULL }
};
#endif

static int
hello_match(device_t parent, cfdata_t match, void *aux)
{
	return 1;
}

static void
hello_attach(device_t parent, device_t self, void *aux)
{
	struct hello_softc *sc;
	const struct sysctlnode *node;

	if (sc_self)
		return;

	sc = device_private(self);
	sc->sc_dev = self;
	sc_self = self;

	/* Sysctl to provide some control over behaviour */
	sysctl_createv(&sc->sc_log, 0, NULL, &node,
		CTLFLAG_OWNDESC,
		CTLTYPE_NODE, "hello",
		SYSCTL_DESCR("Hello options"),
		NULL, 0, NULL, 0,
		CTL_KERN, CTL_CREATE, CTL_EOL);

	if (node == NULL) {
		printf(": can't create sysctl node\n");
		return;
	}

	sysctl_createv(&sc->sc_log, 0, &node, NULL,
		CTLFLAG_READWRITE | CTLFLAG_OWNDESC,
		CTLTYPE_INT, "maxcount",
		SYSCTL_DESCR("Limit maximum instruction count"),
		NULL, 0, &hello_max_instr, 0,
		CTL_CREATE, CTL_EOL);
}

static int
hello_detach(device_t self, int flags)
{
	struct hello_softc *sc;

	sc = device_private(self);

	if (sc->sc_log != NULL) {
		sysctl_teardown(&sc->sc_log);
		sc->sc_log = NULL;
	}

	return 0;
}

static int
hello_modcmd(modcmd_t cmd, void *arg __unused)
{
#ifdef _MODULE
	devmajor_t cmajor, bmajor;
	int error = 0;

	cmajor = bmajor = NODEVMAJOR;
#endif

	switch (cmd) {
	case MODULE_CMD_INIT:
		printf("Example module loaded.\n");

		error = config_cfdriver_attach(&hello_cd);
		if (error)
			return error;

		error = config_cfattach_attach(hello_cd.cd_name, &hello_ca);
		if (error) {
			config_cfdriver_detach(&hello_cd);
			aprint_error("%s: unable to register cfattach\n",
			hello_cd.cd_name);
			return error;
		}

		error = config_cfdata_attach(hello_cfdata, 1);
		if (error) {
			config_cfattach_detach(hello_cd.cd_name, &hello_ca);
			config_cfdriver_detach(&hello_cd);
			aprint_error("%s: unable to register cfdata\n", hello_cd.cd_name);
			return error;
		}
		error = devsw_attach(hello_cd.cd_name, NULL, &bmajor, &hello_cdevsw, &cmajor);
		if (error) {
			aprint_error("%s: unable to register devsw\n", hello_cd.cd_name);
			config_cfattach_detach(hello_cd.cd_name, &hello_ca);
			config_cfdriver_detach(&hello_cd);
			return error;
		}
		config_attach_pseudo(hello_cfdata);
		break;

	case MODULE_CMD_FINI:
		printf("Example module unloaded.\n");
#ifdef _MODULE
		error = config_cfdata_detach(hello_cfdata);
		if (error)
			return error;

			config_cfattach_detach(hello_cd.cd_name, &hello_ca);
			config_cfdriver_detach(&hello_cd);
			devsw_detach(NULL, &hello_cdevsw);
#endif

		break;

	case MODULE_CMD_STAT:
		printf("Example module status queried.\n");
		break;

	default:
		return ENOTTY;
	}

	return 0;
}