Annotation of prex-old/dev/gen/null.c, Revision 1.1.1.1
1.1 nbrk 1: /*-
2: * Copyright (c) 2005-2006, Kohsuke Ohtani
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: * 2. Redistributions in binary form must reproduce the above copyright
11: * notice, this list of conditions and the following disclaimer in the
12: * documentation and/or other materials provided with the distribution.
13: * 3. Neither the name of the author nor the names of any co-contributors
14: * may be used to endorse or promote products derived from this software
15: * without specific prior written permission.
16: *
17: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
18: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20: * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
21: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27: * SUCH DAMAGE.
28: */
29:
30: /*
31: * null.c - null device
32: */
33:
34: #include <driver.h>
35:
36: static int null_read(device_t dev, char *buf, size_t *nbyte, int blkno);
37: static int null_write(device_t dev, char *buf, size_t *nbyte, int blkno);
38: static int null_init(void);
39:
40: /*
41: * Driver structure
42: */
43: struct driver null_drv = {
44: /* name */ "NULL device",
45: /* order */ 2,
46: /* init */ null_init,
47: };
48:
49: static struct devio null_io = {
50: /* open */ NULL,
51: /* close */ NULL,
52: /* read */ null_read,
53: /* write */ null_write,
54: /* ioctl */ NULL,
55: /* event */ NULL,
56: };
57:
58: static device_t null_dev; /* Device object */
59:
60: /*
61: * Always returns 0 bytes as the read size.
62: */
63: static int
64: null_read(device_t dev, char *buf, size_t *nbyte, int blkno)
65: {
66:
67: *nbyte = 0;
68: return 0;
69: }
70:
71: /*
72: * Data written to this device is discarded.
73: */
74: static int
75: null_write(device_t dev, char *buf, size_t *nbyte, int blkno)
76: {
77:
78: return 0;
79: }
80:
81:
82: /*
83: * Initialize
84: */
85: static int
86: null_init(void)
87: {
88:
89: /* Create device object */
90: null_dev = device_create(&null_io, "null", DF_CHR);
91: ASSERT(null_dev);
92: return 0;
93: }
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