drivers/pps/clients/pps-ldisc.c

   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
  22 #include <linux/module.h>
  23 #include <linux/serial_core.h>
  24 #include <linux/tty.h>
  25 #include <linux/pps_kernel.h>
  26
  27 #define PPS_TTY_MAGIC           0x0001
  28
  29 static void pps_tty_dcd_change(struct tty_struct *tty, unsigned int status,
  30                                 struct timespec *ts)
  31 {
  32         int id = (long)tty->disc_data;
  33         struct timespec __ts;
  34         struct pps_ktime pps_ts;
  35
  36         /* First of all we get the time stamp... */
  37         getnstimeofday(&__ts);
  38
  39         /* Does caller give us a timestamp? */
  40         if (ts) {       /* Yes. Let's use it! */
  41                 pps_ts.sec = ts->tv_sec;
  42                 pps_ts.nsec = ts->tv_nsec;
  43         } else {        /* No. Do it ourself! */
  44                 pps_ts.sec = __ts.tv_sec;
  45                 pps_ts.nsec = __ts.tv_nsec;
  46         }
  47
  48         /* Now do the PPS event report */
  49         pps_event(id, &pps_ts, status ? PPS_CAPTUREASSERT : PPS_CAPTURECLEAR,
  50                         NULL);
  51
  52         pr_debug("PPS %s at %lu on source #%d\n",
  53                         status ? "assert" : "clear", jiffies, id);
  54 }
  55
  56 static int (*alias_n_tty_open)(struct tty_struct *tty);
  57
  58 static int pps_tty_open(struct tty_struct *tty)
  59 {
  60         struct pps_source_info info;
  61         struct tty_driver *drv = tty->driver;
  62         int index = tty->index + drv->name_base;
  63         int ret;
  64
  65         info.owner = THIS_MODULE;
  66         info.dev = NULL;
  67         snprintf(info.name, PPS_MAX_NAME_LEN, "%s%d", drv->driver_name, index);
  68         snprintf(info.path, PPS_MAX_NAME_LEN, "/dev/%s%d", drv->name, index);
  69         info.mode = PPS_CAPTUREBOTH | \
  70                         PPS_OFFSETASSERT | PPS_OFFSETCLEAR | \
  71                         PPS_CANWAIT | PPS_TSFMT_TSPEC;
  72
  73         ret = pps_register_source(&info, PPS_CAPTUREBOTH | \
  74                                 PPS_OFFSETASSERT | PPS_OFFSETCLEAR);
  75         if (ret < 0) {
  76                 pr_err("cannot register PPS source \"%s\"\n", info.path);
  77                 return ret;
  78         }
  79         tty->disc_data = (void *)(long)ret;
  80
  81         /* Should open N_TTY ldisc too */
  82         ret = alias_n_tty_open(tty);
  83         if (ret < 0)
  84                 pps_unregister_source((long)tty->disc_data);
  85
  86         pr_info("PPS source #%d \"%s\" added\n", ret, info.path);
  87
  88         return 0;
  89 }
  90
  91 static void (*alias_n_tty_close)(struct tty_struct *tty);
  92
  93 static void pps_tty_close(struct tty_struct *tty)
  94 {
  95         int id = (long)tty->disc_data;
  96
  97         pps_unregister_source(id);
  98         alias_n_tty_close(tty);
  99
 100         pr_info("PPS source #%d removed\n", id);
 101 }
 102
 103 static struct tty_ldisc_ops pps_ldisc_ops;
 104
 105 /*
 106  * Module stuff
 107  */
 108
 109 static int __init pps_tty_init(void)
 110 {
 111         int err;
 112
 113         /* Inherit the N_TTY's ops */
 114         n_tty_inherit_ops(&pps_ldisc_ops);
 115
 116         /* Save N_TTY's open()/close() methods */
 117         alias_n_tty_open = pps_ldisc_ops.open;
 118         alias_n_tty_close = pps_ldisc_ops.close;
 119
 120         /* Init PPS_TTY data */
 121         pps_ldisc_ops.owner = THIS_MODULE;
 122         pps_ldisc_ops.magic = PPS_TTY_MAGIC;
 123         pps_ldisc_ops.name = "pps_tty";
 124         pps_ldisc_ops.dcd_change = pps_tty_dcd_change;
 125         pps_ldisc_ops.open = pps_tty_open;
 126         pps_ldisc_ops.close = pps_tty_close;
 127
 128         err = tty_register_ldisc(N_PPS, &pps_ldisc_ops);
 129         if (err)
 130                 pr_err("can't register PPS line discipline\n");
 131         else
 132                 pr_info("PPS line discipline registered\n");
 133
 134         return err;
 135 }
 136
 137 static void __exit pps_tty_cleanup(void)
 138 {
 139         int err;
 140
 141         err = tty_unregister_ldisc(N_PPS);
 142         if (err)
 143                 pr_err("can't unregister PPS line discipline\n");
 144         else
 145                 pr_info("PPS line discipline removed\n");
 146 }
 147
 148 module_init(pps_tty_init);
 149 module_exit(pps_tty_cleanup);
 150
 151 MODULE_ALIAS_LDISC(N_PPS);
 152 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
 153 MODULE_DESCRIPTION("PPS TTY device driver");
 154 MODULE_LICENSE("GPL");