Annotation of prex/dev/gen/zero.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: * zero.c - zero device
32: */
33:
34: #include <driver.h>
35:
36: static int zero_read(device_t, char *, size_t *, int);
37: static int zero_write(device_t, char *, size_t *, int);
38: static int zero_init(void);
39:
40: /*
41: * Driver structure
42: */
43: struct driver zero_drv = {
44: /* name */ "Zero device",
45: /* order */ 2,
46: /* init */ zero_init,
47: };
48:
49: /*
50: * Device I/O table
51: */
52: static struct devio zero_io = {
53: /* open */ NULL,
54: /* close */ NULL,
55: /* read */ zero_read,
56: /* write */ zero_write,
57: /* ioctl */ NULL,
58: /* event */ NULL,
59: };
60:
61: static device_t zero_dev; /* Device object */
62:
63: /*
64: * Read
65: */
66: static int
67: zero_read(device_t dev, char *buf, size_t *nbyte, int blkno)
68: {
69: void *kbuf;
70:
71: /* Translate buffer address to kernel address */
72: kbuf = kmem_map(buf, *nbyte);
73: if (kbuf == NULL)
74: return EFAULT;
75: memset(kbuf, 0, *nbyte);
76: return 0;
77: }
78:
79: /*
80: * Writing data to this device is ignored.
81: */
82: static int
83: zero_write(device_t dev, char *buf, size_t *nbyte, int blkno)
84: {
85:
86: return 0;
87: }
88:
89:
90: /*
91: * Initialize
92: */
93: static int
94: zero_init(void)
95: {
96:
97: /* Create device object */
98: zero_dev = device_create(&zero_io, "zero", DF_CHR);
99: ASSERT(zero_dev);
100: return 0;
101: }
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