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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  23
  24 #include <linux/module.h>
  25 #include <linux/serial_core.h>
  26 #include <linux/tty.h>
  27 #include <linux/pps_kernel.h>
  28 #include <linux/bug.h>
  29
  30 #define PPS_TTY_MAGIC           0x0001
  31
  32 static void pps_tty_dcd_change(struct tty_struct *tty, unsigned int status,
  33                                 struct pps_event_time *ts)
  34 {
  35         struct pps_device *pps = pps_lookup_dev(tty);
  36
  37         /*
  38          * This should never fail, but the ldisc locking is very
  39          * convoluted, so don't crash just in case.
  40          */
  41         if (WARN_ON_ONCE(pps == NULL))
  42                 return;
  43
  44         /* Now do the PPS event report */
  45         pps_event(pps, ts, status ? PPS_CAPTUREASSERT :
  46                         PPS_CAPTURECLEAR, NULL);
  47
  48         dev_dbg(pps->dev, "PPS %s at %lu\n",
  49                         status ? "assert" : "clear", jiffies);
  50 }
  51
  52 static int (*alias_n_tty_open)(struct tty_struct *tty);
  53
  54 static int pps_tty_open(struct tty_struct *tty)
  55 {
  56         struct pps_source_info info;
  57         struct tty_driver *drv = tty->driver;
  58         int index = tty->index + drv->name_base;
  59         struct pps_device *pps;
  60         int ret;
  61
  62         info.owner = THIS_MODULE;
  63         info.dev = NULL;
  64         snprintf(info.name, PPS_MAX_NAME_LEN, "%s%d", drv->driver_name, index);
  65         snprintf(info.path, PPS_MAX_NAME_LEN, "/dev/%s%d", drv->name, index);
  66         info.mode = PPS_CAPTUREBOTH | \
  67                         PPS_OFFSETASSERT | PPS_OFFSETCLEAR | \
  68                         PPS_CANWAIT | PPS_TSFMT_TSPEC;
  69
  70         pps = pps_register_source(&info, PPS_CAPTUREBOTH | \
  71                                 PPS_OFFSETASSERT | PPS_OFFSETCLEAR);
  72         if (pps == NULL) {
  73                 pr_err("cannot register PPS source \"%s\"\n", info.path);
  74                 return -ENOMEM;
  75         }
  76         pps->lookup_cookie = tty;
  77
  78         /* Now open the base class N_TTY ldisc */
  79         ret = alias_n_tty_open(tty);
  80         if (ret < 0) {
  81                 pr_err("cannot open tty ldisc \"%s\"\n", info.path);
  82                 goto err_unregister;
  83         }
  84
  85         dev_info(pps->dev, "source \"%s\" added\n", info.path);
  86
  87         return 0;
  88
  89 err_unregister:
  90         pps_unregister_source(pps);
  91         return ret;
  92 }
  93
  94 static void (*alias_n_tty_close)(struct tty_struct *tty);
  95
  96 static void pps_tty_close(struct tty_struct *tty)
  97 {
  98         struct pps_device *pps = pps_lookup_dev(tty);
  99
 100         alias_n_tty_close(tty);
 101
 102         if (WARN_ON(!pps))
 103                 return;
 104
 105         dev_info(pps->dev, "removed\n");
 106         pps_unregister_source(pps);
 107 }
 108
 109 static struct tty_ldisc_ops pps_ldisc_ops;
 110
 111 /*
 112  * Module stuff
 113  */
 114
 115 static int __init pps_tty_init(void)
 116 {
 117         int err;
 118
 119         /* Inherit the N_TTY's ops */
 120         n_tty_inherit_ops(&pps_ldisc_ops);
 121
 122         /* Save N_TTY's open()/close() methods */
 123         alias_n_tty_open = pps_ldisc_ops.open;
 124         alias_n_tty_close = pps_ldisc_ops.close;
 125
 126         /* Init PPS_TTY data */
 127         pps_ldisc_ops.owner = THIS_MODULE;
 128         pps_ldisc_ops.magic = PPS_TTY_MAGIC;
 129         pps_ldisc_ops.name = "pps_tty";
 130         pps_ldisc_ops.dcd_change = pps_tty_dcd_change;
 131         pps_ldisc_ops.open = pps_tty_open;
 132         pps_ldisc_ops.close = pps_tty_close;
 133
 134         err = tty_register_ldisc(N_PPS, &pps_ldisc_ops);
 135         if (err)
 136                 pr_err("can't register PPS line discipline\n");
 137         else
 138                 pr_info("PPS line discipline registered\n");
 139
 140         return err;
 141 }
 142
 143 static void __exit pps_tty_cleanup(void)
 144 {
 145         int err;
 146
 147         err = tty_unregister_ldisc(N_PPS);
 148         if (err)
 149                 pr_err("can't unregister PPS line discipline\n");
 150         else
 151                 pr_info("PPS line discipline removed\n");
 152 }
 153
 154 module_init(pps_tty_init);
 155 module_exit(pps_tty_cleanup);
 156
 157 MODULE_ALIAS_LDISC(N_PPS);
 158 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
 159 MODULE_DESCRIPTION("PPS TTY device driver");
 160 MODULE_LICENSE("GPL");