console-read.c 3.0 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. * console-read: This example demonstrates the easiest possible way to
  36. * block a client system call: by blocking the driver itself. Not
  37. * recommended for anything but the most trivial drivers -- if you
  38. * need a template from which to start on a real driver, use pager.c
  39. * instead.
  40. *
  41. */
  42. #include <stdio.h>
  43. #include <string.h>
  44. #include <errno.h>
  45. #include "fusd.h"
  46. #define MIN(x, y) ((x) < (y) ? (x) : (y))
  47. int do_open_or_close(struct fusd_file_info *file)
  48. {
  49. return 0; /* attempts to open and close this file always succeed */
  50. }
  51. /* EXAMPLE START console-read.c */
  52. ssize_t do_read(struct fusd_file_info *file, char *user_buffer,
  53. size_t user_length, loff_t *offset)
  54. {
  55. char buf[128];
  56. if (*offset > 0)
  57. return 0;
  58. /* print a prompt */
  59. printf("Got a read from pid %d. What do we say?\n> ", file->pid);
  60. fflush(stdout);
  61. /* get a response from the console */
  62. if (fgets(buf, sizeof(buf) - 1, stdin) == NULL)
  63. return 0;
  64. /* compute length of the response, and return */
  65. user_length = MIN(user_length, strlen(buf));
  66. memcpy(user_buffer, buf, user_length);
  67. *offset += user_length;
  68. return user_length;
  69. }
  70. /* EXAMPLE STOP */
  71. int main(int argc, char *argv[])
  72. {
  73. struct fusd_file_operations fops = {
  74. open: do_open_or_close,
  75. read: do_read,
  76. close: do_open_or_close };
  77. if (fusd_register("/dev/console-read", "test", "console-read", 0666, NULL, &fops) < 0)
  78. perror("Unable to register device");
  79. else {
  80. printf("/dev/console-read should now exist - calling fusd_run...\n");
  81. fusd_run();
  82. }
  83. return 0;
  84. }