scoutos / prex-0.9.0 / bsp / drv / dev / misc / zero.c @ 03e9c04a
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1 | 03e9c04a | Brad Neuman | /*-
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2 | * Copyright (c) 2005-2006, Kohsuke Ohtani
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3 | * All rights reserved.
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4 | *
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5 | * Redistribution and use in source and binary forms, with or without
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6 | * modification, are permitted provided that the following conditions
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7 | * are met:
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8 | * 1. Redistributions of source code must retain the above copyright
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9 | * notice, this list of conditions and the following disclaimer.
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10 | * 2. Redistributions in binary form must reproduce the above copyright
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11 | * notice, this list of conditions and the following disclaimer in the
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12 | * documentation and/or other materials provided with the distribution.
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13 | * 3. Neither the name of the author nor the names of any co-contributors
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14 | * may be used to endorse or promote products derived from this software
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15 | * without specific prior written permission.
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16 | *
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17 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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18 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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19 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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20 | * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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21 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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22 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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23 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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24 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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25 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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26 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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27 | * SUCH DAMAGE.
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28 | */
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29 | |||
30 | /*
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31 | * zero.c - zero device
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32 | */
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33 | |||
34 | #include <driver.h> |
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35 | |||
36 | static int zero_read(device_t, char *, size_t *, int); |
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37 | static int zero_write(device_t, char *, size_t *, int); |
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38 | static int zero_init(struct driver *); |
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39 | |||
40 | static struct devops zero_devops = { |
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41 | /* open */ no_open,
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42 | /* close */ no_close,
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43 | /* read */ zero_read,
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44 | /* write */ zero_write,
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45 | /* ioctl */ no_ioctl,
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46 | /* devctl */ no_devctl,
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47 | }; |
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48 | |||
49 | struct driver zero_driver = {
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50 | /* name */ "zero", |
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51 | /* devops */ &zero_devops,
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52 | /* devsz */ 0, |
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53 | /* flags */ 0, |
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54 | /* probe */ NULL, |
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55 | /* init */ zero_init,
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56 | /* shutdown */ NULL, |
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57 | }; |
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58 | |||
59 | /*
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60 | * Reading from this device will just fill the buffer with zero.
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61 | */
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62 | static int |
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63 | zero_read(device_t dev, char *buf, size_t *nbyte, int blkno) |
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64 | { |
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65 | void *p;
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66 | |||
67 | /* Translate buffer address to kernel address. */
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68 | if ((p = kmem_map(buf, *nbyte)) == NULL) |
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69 | return EFAULT;
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70 | |||
71 | memset(p, 0, *nbyte);
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72 | return 0; |
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73 | } |
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74 | |||
75 | /*
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76 | * Writing data to this device is ignored.
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77 | */
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78 | static int |
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79 | zero_write(device_t dev, char *buf, size_t *nbyte, int blkno) |
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80 | { |
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81 | |||
82 | return 0; |
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83 | } |
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84 | |||
85 | static int |
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86 | zero_init(struct driver *self)
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87 | { |
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88 | |||
89 | device_create(self, "zero", D_CHR);
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90 | return 0; |
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91 | } |