pps-ldisc.c 3.8 KB

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  1. /*
  2. * pps-ldisc.c -- PPS line discipline
  3. *
  4. *
  5. * Copyright (C) 2008 Rodolfo Giometti <giometti@linux.it>
  6. *
  7. * This program is free software; you can redistribute it and/or modify
  8. * it under the terms of the GNU General Public License as published by
  9. * the Free Software Foundation; either version 2 of the License, or
  10. * (at your option) any later version.
  11. *
  12. * This program is distributed in the hope that it will be useful,
  13. * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14. * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  15. * GNU General Public License for more details.
  16. *
  17. * You should have received a copy of the GNU General Public License
  18. * along with this program; if not, write to the Free Software
  19. * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20. */
  21. #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  22. #include <linux/module.h>
  23. #include <linux/serial_core.h>
  24. #include <linux/tty.h>
  25. #include <linux/pps_kernel.h>
  26. #define PPS_TTY_MAGIC 0x0001
  27. static void pps_tty_dcd_change(struct tty_struct *tty, unsigned int status,
  28. struct pps_event_time *ts)
  29. {
  30. struct pps_device *pps = pps_lookup_dev(tty);
  31. BUG_ON(pps == NULL);
  32. /* Now do the PPS event report */
  33. pps_event(pps, ts, status ? PPS_CAPTUREASSERT :
  34. PPS_CAPTURECLEAR, NULL);
  35. dev_dbg(pps->dev, "PPS %s at %lu\n",
  36. status ? "assert" : "clear", jiffies);
  37. }
  38. static int (*alias_n_tty_open)(struct tty_struct *tty);
  39. static int pps_tty_open(struct tty_struct *tty)
  40. {
  41. struct pps_source_info info;
  42. struct tty_driver *drv = tty->driver;
  43. int index = tty->index + drv->name_base;
  44. struct pps_device *pps;
  45. int ret;
  46. info.owner = THIS_MODULE;
  47. info.dev = NULL;
  48. snprintf(info.name, PPS_MAX_NAME_LEN, "%s%d", drv->driver_name, index);
  49. snprintf(info.path, PPS_MAX_NAME_LEN, "/dev/%s%d", drv->name, index);
  50. info.mode = PPS_CAPTUREBOTH | \
  51. PPS_OFFSETASSERT | PPS_OFFSETCLEAR | \
  52. PPS_CANWAIT | PPS_TSFMT_TSPEC;
  53. pps = pps_register_source(&info, PPS_CAPTUREBOTH | \
  54. PPS_OFFSETASSERT | PPS_OFFSETCLEAR);
  55. if (pps == NULL) {
  56. pr_err("cannot register PPS source \"%s\"\n", info.path);
  57. return -ENOMEM;
  58. }
  59. pps->lookup_cookie = tty;
  60. /* Now open the base class N_TTY ldisc */
  61. ret = alias_n_tty_open(tty);
  62. if (ret < 0) {
  63. pr_err("cannot open tty ldisc \"%s\"\n", info.path);
  64. goto err_unregister;
  65. }
  66. dev_info(pps->dev, "source \"%s\" added\n", info.path);
  67. return 0;
  68. err_unregister:
  69. pps_unregister_source(pps);
  70. return ret;
  71. }
  72. static void (*alias_n_tty_close)(struct tty_struct *tty);
  73. static void pps_tty_close(struct tty_struct *tty)
  74. {
  75. struct pps_device *pps = pps_lookup_dev(tty);
  76. alias_n_tty_close(tty);
  77. dev_info(pps->dev, "removed\n");
  78. pps_unregister_source(pps);
  79. }
  80. static struct tty_ldisc_ops pps_ldisc_ops;
  81. /*
  82. * Module stuff
  83. */
  84. static int __init pps_tty_init(void)
  85. {
  86. int err;
  87. /* Inherit the N_TTY's ops */
  88. n_tty_inherit_ops(&pps_ldisc_ops);
  89. /* Save N_TTY's open()/close() methods */
  90. alias_n_tty_open = pps_ldisc_ops.open;
  91. alias_n_tty_close = pps_ldisc_ops.close;
  92. /* Init PPS_TTY data */
  93. pps_ldisc_ops.owner = THIS_MODULE;
  94. pps_ldisc_ops.magic = PPS_TTY_MAGIC;
  95. pps_ldisc_ops.name = "pps_tty";
  96. pps_ldisc_ops.dcd_change = pps_tty_dcd_change;
  97. pps_ldisc_ops.open = pps_tty_open;
  98. pps_ldisc_ops.close = pps_tty_close;
  99. err = tty_register_ldisc(N_PPS, &pps_ldisc_ops);
  100. if (err)
  101. pr_err("can't register PPS line discipline\n");
  102. else
  103. pr_info("PPS line discipline registered\n");
  104. return err;
  105. }
  106. static void __exit pps_tty_cleanup(void)
  107. {
  108. int err;
  109. err = tty_unregister_ldisc(N_PPS);
  110. if (err)
  111. pr_err("can't unregister PPS line discipline\n");
  112. else
  113. pr_info("PPS line discipline removed\n");
  114. }
  115. module_init(pps_tty_init);
  116. module_exit(pps_tty_cleanup);
  117. MODULE_ALIAS_LDISC(N_PPS);
  118. MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
  119. MODULE_DESCRIPTION("PPS TTY device driver");
  120. MODULE_LICENSE("GPL");