drums2.c 4.1 KB

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  1. /*
  2. *
  3. * Copyright (c) 2003 The Regents of the University of California. All
  4. * rights reserved.
  5. *
  6. * Redistribution and use in source and binary forms, with or without
  7. * modification, are permitted provided that the following conditions
  8. * are met:
  9. *
  10. * - Redistributions of source code must retain the above copyright
  11. * notice, this list of conditions and the following disclaimer.
  12. *
  13. * - Neither the name of the University nor the names of its
  14. * contributors may be used to endorse or promote products derived
  15. * from this software without specific prior written permission.
  16. *
  17. * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS''
  18. * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  19. * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
  20. * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR
  21. * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  22. * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  23. * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  24. * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  25. * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  26. * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  27. * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  28. *
  29. */
  30. /*
  31. * FUSD - The Framework for UserSpace Devices - Example program
  32. *
  33. * Jeremy Elson <jelson@circlemud.org>
  34. *
  35. * drums2.c: Another example of how to pass data to a callback,
  36. * inspired by Alessandro Rubini's similar example in his article for
  37. * Linux Magazine (http://www.linux.it/kerneldocs/devfs/)
  38. *
  39. * Like the original drums.c, this example creates a bunch of devices
  40. * in the /dev/drums directory: /dev/drums/bam, /dev/drums/bum, etc.
  41. * However, it also uses the private_data structure to keep per-file
  42. * state, and return a string unique to each user of the device.
  43. *
  44. * Note, unlike the original drums.c, this driver does not use *offset
  45. * to remember if this user has read before; cat /dev/drums/X will
  46. * read infinitely
  47. *
  48. */
  49. #include <stdio.h>
  50. #include <stdlib.h>
  51. #include <string.h>
  52. #include <errno.h>
  53. #include <unistd.h>
  54. #include "fusd.h"
  55. #define MIN(x, y) ((x) < (y) ? (x) : (y))
  56. /* EXAMPLE START drums2.c */
  57. struct drum_info {
  58. char *name;
  59. int num_users;
  60. } drums[] = {
  61. { "bam", 0 },
  62. { "bum", 0 },
  63. /* ... */
  64. /* EXAMPLE STOP */
  65. { "beat", 0 },
  66. { "boom", 0 },
  67. { "bang", 0 },
  68. { "crash", 0 },
  69. /* EXAMPLE START drums2.c */
  70. { NULL, 0 }
  71. };
  72. int drums_open(struct fusd_file_info *file)
  73. {
  74. /* file->device_info is what we passed to fusd_register when we
  75. * registered the device. It's a pointer into the "drums" struct. */
  76. struct drum_info *d = (struct drum_info *) file->device_info;
  77. int *user_num = calloc(1, sizeof(*user_num));
  78. /* Store this user's unique user number in their private_data */
  79. *user_num = ++(d->num_users);
  80. file->private_data = (void *) user_num;
  81. return 0; /* return success */
  82. }
  83. ssize_t drums_read(struct fusd_file_info *file, char *user_buffer,
  84. size_t user_length, loff_t *offset)
  85. {
  86. struct drum_info *d = (struct drum_info *) file->device_info;
  87. int len;
  88. char sound[128];
  89. sprintf(sound, "You are user %d to hear a drum go '%s'!\n",
  90. *(int *) file->private_data, d->name);
  91. len = MIN(user_length, strlen(sound));
  92. memcpy(user_buffer, sound, len);
  93. *offset += len;
  94. return len;
  95. }
  96. /* EXAMPLE STOP */
  97. int drums_close(struct fusd_file_info *file)
  98. {
  99. return 0; /* closes always succeed */
  100. }
  101. struct fusd_file_operations drums_fops = {
  102. open: drums_open,
  103. read: drums_read,
  104. close: drums_close
  105. };
  106. /* EXAMPLE START drums2.c */
  107. int main(int argc, char *argv[])
  108. {
  109. struct drum_info *d;
  110. char buf[128];
  111. char devname[128];
  112. for (d = drums; d->name != NULL; d++) {
  113. sprintf(buf, "/dev/drums/%s", d->name);
  114. sprintf(devname, "drum%s", d->name);
  115. if (fusd_register(buf, "drums", devname, 0666, d, &drums_fops) < 0)
  116. fprintf(stderr, "%s register failed: %m\n", d->name);
  117. }
  118. /* ... */
  119. /* EXAMPLE STOP */
  120. fprintf(stderr, "calling fusd_run...\n");
  121. fusd_run();
  122. return 0;
  123. }