pps-ldisc.c 3.3 KB

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  1. // SPDX-License-Identifier: GPL-2.0-or-later
  2. /*
  3. * pps-ldisc.c -- PPS line discipline
  4. *
  5. * Copyright (C) 2008 Rodolfo Giometti <giometti@linux.it>
  6. */
  7. #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  8. #include <linux/module.h>
  9. #include <linux/serial_core.h>
  10. #include <linux/tty.h>
  11. #include <linux/pps_kernel.h>
  12. #include <linux/bug.h>
  13. #define PPS_TTY_MAGIC 0x0001
  14. static void pps_tty_dcd_change(struct tty_struct *tty, unsigned int status)
  15. {
  16. struct pps_device *pps;
  17. struct pps_event_time ts;
  18. pps_get_ts(&ts);
  19. pps = pps_lookup_dev(tty);
  20. /*
  21. * This should never fail, but the ldisc locking is very
  22. * convoluted, so don't crash just in case.
  23. */
  24. if (WARN_ON_ONCE(pps == NULL))
  25. return;
  26. /* Now do the PPS event report */
  27. pps_event(pps, &ts, status ? PPS_CAPTUREASSERT :
  28. PPS_CAPTURECLEAR, NULL);
  29. dev_dbg(pps->dev, "PPS %s at %lu\n",
  30. status ? "assert" : "clear", jiffies);
  31. }
  32. static int (*alias_n_tty_open)(struct tty_struct *tty);
  33. static int pps_tty_open(struct tty_struct *tty)
  34. {
  35. struct pps_source_info info;
  36. struct tty_driver *drv = tty->driver;
  37. int index = tty->index + drv->name_base;
  38. struct pps_device *pps;
  39. int ret;
  40. info.owner = THIS_MODULE;
  41. info.dev = NULL;
  42. snprintf(info.name, PPS_MAX_NAME_LEN, "%s%d", drv->driver_name, index);
  43. snprintf(info.path, PPS_MAX_NAME_LEN, "/dev/%s%d", drv->name, index);
  44. info.mode = PPS_CAPTUREBOTH | \
  45. PPS_OFFSETASSERT | PPS_OFFSETCLEAR | \
  46. PPS_CANWAIT | PPS_TSFMT_TSPEC;
  47. pps = pps_register_source(&info, PPS_CAPTUREBOTH | \
  48. PPS_OFFSETASSERT | PPS_OFFSETCLEAR);
  49. if (IS_ERR(pps)) {
  50. pr_err("cannot register PPS source \"%s\"\n", info.path);
  51. return PTR_ERR(pps);
  52. }
  53. pps->lookup_cookie = tty;
  54. /* Now open the base class N_TTY ldisc */
  55. ret = alias_n_tty_open(tty);
  56. if (ret < 0) {
  57. pr_err("cannot open tty ldisc \"%s\"\n", info.path);
  58. goto err_unregister;
  59. }
  60. dev_info(pps->dev, "source \"%s\" added\n", info.path);
  61. return 0;
  62. err_unregister:
  63. pps_unregister_source(pps);
  64. return ret;
  65. }
  66. static void (*alias_n_tty_close)(struct tty_struct *tty);
  67. static void pps_tty_close(struct tty_struct *tty)
  68. {
  69. struct pps_device *pps = pps_lookup_dev(tty);
  70. alias_n_tty_close(tty);
  71. if (WARN_ON(!pps))
  72. return;
  73. dev_info(pps->dev, "removed\n");
  74. pps_unregister_source(pps);
  75. }
  76. static struct tty_ldisc_ops pps_ldisc_ops;
  77. /*
  78. * Module stuff
  79. */
  80. static int __init pps_tty_init(void)
  81. {
  82. int err;
  83. /* Inherit the N_TTY's ops */
  84. n_tty_inherit_ops(&pps_ldisc_ops);
  85. /* Save N_TTY's open()/close() methods */
  86. alias_n_tty_open = pps_ldisc_ops.open;
  87. alias_n_tty_close = pps_ldisc_ops.close;
  88. /* Init PPS_TTY data */
  89. pps_ldisc_ops.owner = THIS_MODULE;
  90. pps_ldisc_ops.magic = PPS_TTY_MAGIC;
  91. pps_ldisc_ops.name = "pps_tty";
  92. pps_ldisc_ops.dcd_change = pps_tty_dcd_change;
  93. pps_ldisc_ops.open = pps_tty_open;
  94. pps_ldisc_ops.close = pps_tty_close;
  95. err = tty_register_ldisc(N_PPS, &pps_ldisc_ops);
  96. if (err)
  97. pr_err("can't register PPS line discipline\n");
  98. else
  99. pr_info("PPS line discipline registered\n");
  100. return err;
  101. }
  102. static void __exit pps_tty_cleanup(void)
  103. {
  104. int err;
  105. err = tty_unregister_ldisc(N_PPS);
  106. if (err)
  107. pr_err("can't unregister PPS line discipline\n");
  108. else
  109. pr_info("PPS line discipline removed\n");
  110. }
  111. module_init(pps_tty_init);
  112. module_exit(pps_tty_cleanup);
  113. MODULE_ALIAS_LDISC(N_PPS);
  114. MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
  115. MODULE_DESCRIPTION("PPS TTY device driver");
  116. MODULE_LICENSE("GPL");