null.c revision 62843 
1/*-
2 * Copyright (c) 2000 Mark R. V. Murray & Jeroen C. van Gelderen
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer
10 *    in this position and unchanged.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 *
26 * $FreeBSD: head/sys/dev/null/null.c 62843 2000-07-09 12:29:24Z markm $
27 */
28
29#include <sys/param.h>
30#include <sys/systm.h>
31#include <sys/conf.h>
32#include <sys/uio.h>
33#include <sys/kernel.h>
34#include <sys/malloc.h>
35#include <sys/module.h>
36#include <sys/bus.h>
37#include <machine/bus.h>
38#include <machine/resource.h>
39#include <sys/rman.h>
40
41/* For use with destroy_dev(9). */
42static dev_t null_dev;
43static dev_t zero_dev;
44
45static d_write_t null_write;
46static d_read_t zero_read;
47
48#define CDEV_MAJOR	2
49#define NULL_MINOR	2
50#define ZERO_MINOR	12
51
52static struct cdevsw null_cdevsw = {
53	/* open */	(d_open_t *)nullop,
54	/* close */	(d_close_t *)nullop,
55	/* read */	(d_read_t *)nullop,
56	/* write */	null_write,
57	/* ioctl */	noioctl,
58	/* poll */	nopoll,
59	/* mmap */	nommap,
60	/* strategy */	nostrategy,
61	/* name */	"null",
62	/* maj */	CDEV_MAJOR,
63	/* dump */	nodump,
64	/* psize */	nopsize,
65	/* flags */	0,
66	/* bmaj */	-1
67};
68
69static struct cdevsw zero_cdevsw = {
70	/* open */	(d_open_t *)nullop,
71	/* close */	(d_close_t *)nullop,
72	/* read */	zero_read,
73	/* write */	null_write,
74	/* ioctl */	noioctl,
75	/* poll */	nopoll,
76	/* mmap */	nommap,
77	/* strategy */	nostrategy,
78	/* name */	"zero",
79	/* maj */	CDEV_MAJOR,
80	/* dump */	nodump,
81	/* psize */	nopsize,
82	/* flags */	D_MMAP_ANON,
83	/* bmaj */	-1
84};
85
86static void *zbuf;
87
88static int
89null_write(dev_t dev, struct uio *uio, int flag)
90{
91	uio->uio_resid = 0;
92	return 0;
93}
94
95static int
96zero_read(dev_t dev, struct uio *uio, int flag)
97{
98	u_int c;
99	int error = 0;
100
101	while (uio->uio_resid > 0 && error == 0) {
102		c = min(uio->uio_resid, PAGE_SIZE);
103		error = uiomove(zbuf, c, uio);
104	}
105	return error;
106}
107
108static int
109null_modevent(module_t mod, int type, void *data)
110{
111	switch(type) {
112	case MOD_LOAD:
113		if (bootverbose)
114			printf("nulldev: <null device, zero device>\n");
115		zbuf = (void *)malloc(PAGE_SIZE, M_TEMP, M_WAITOK);
116		bzero(zbuf, PAGE_SIZE);
117		zero_dev = make_dev(&zero_cdevsw, ZERO_MINOR, UID_ROOT,
118			GID_WHEEL, 0666, "zero");
119		null_dev = make_dev(&null_cdevsw, NULL_MINOR, UID_ROOT,
120			GID_WHEEL, 0666, "null");
121		return 0;
122
123	case MOD_UNLOAD:
124		destroy_dev(null_dev);
125		destroy_dev(zero_dev);
126		free(zbuf, M_TEMP);
127		return 0;
128
129	case MOD_SHUTDOWN:
130		return 0;
131
132	default:
133		return EOPNOTSUPP;
134	}
135}
136
137DEV_MODULE(nulldev, null_modevent, NULL);
138