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
  29 #define PPS_TTY_MAGIC           0x0001
  30
  31 static void pps_tty_dcd_change(struct tty_struct *tty, unsigned int status,
  32                                 struct pps_event_time *ts)
  33 {
  34         struct pps_device *pps = pps_lookup_dev(tty);
  35
  36         BUG_ON(pps == NULL);
  37
  38         /* Now do the PPS event report */
  39         pps_event(pps, ts, status ? PPS_CAPTUREASSERT :
  40                         PPS_CAPTURECLEAR, NULL);
  41
  42         dev_dbg(pps->dev, "PPS %s at %lu\n",
  43                         status ? "assert" : "clear", jiffies);
  44 }
  45
  46 static int (*alias_n_tty_open)(struct tty_struct *tty);
  47
  48 static int pps_tty_open(struct tty_struct *tty)
  49 {
  50         struct pps_source_info info;
  51         struct tty_driver *drv = tty->driver;
  52         int index = tty->index + drv->name_base;
  53         struct pps_device *pps;
  54         int ret;
  55
  56         info.owner = THIS_MODULE;
  57         info.dev = NULL;
  58         snprintf(info.name, PPS_MAX_NAME_LEN, "%s%d", drv->driver_name, index);
  59         snprintf(info.path, PPS_MAX_NAME_LEN, "/dev/%s%d", drv->name, index);
  60         info.mode = PPS_CAPTUREBOTH | \
  61                         PPS_OFFSETASSERT | PPS_OFFSETCLEAR | \
  62                         PPS_CANWAIT | PPS_TSFMT_TSPEC;
  63
  64         pps = pps_register_source(&info, PPS_CAPTUREBOTH | \
  65                                 PPS_OFFSETASSERT | PPS_OFFSETCLEAR);
  66         if (pps == NULL) {
  67                 pr_err("cannot register PPS source \"%s\"\n", info.path);
  68                 return -ENOMEM;
  69         }
  70         pps->lookup_cookie = tty;
  71
  72         /* Now open the base class N_TTY ldisc */
  73         ret = alias_n_tty_open(tty);
  74         if (ret < 0) {
  75                 pr_err("cannot open tty ldisc \"%s\"\n", info.path);
  76                 goto err_unregister;
  77         }
  78
  79         dev_info(pps->dev, "source \"%s\" added\n", info.path);
  80
  81         return 0;
  82
  83 err_unregister:
  84         pps_unregister_source(pps);
  85         return ret;
  86 }
  87
  88 static void (*alias_n_tty_close)(struct tty_struct *tty);
  89
  90 static void pps_tty_close(struct tty_struct *tty)
  91 {
  92         struct pps_device *pps = pps_lookup_dev(tty);
  93
  94         alias_n_tty_close(tty);
  95
  96         dev_info(pps->dev, "removed\n");
  97         pps_unregister_source(pps);
  98 }
  99
 100 static struct tty_ldisc_ops pps_ldisc_ops;
 101
 102 /*
 103  * Module stuff
 104  */
 105
 106 static int __init pps_tty_init(void)
 107 {
 108         int err;
 109
 110         /* Inherit the N_TTY's ops */
 111         n_tty_inherit_ops(&pps_ldisc_ops);
 112
 113         /* Save N_TTY's open()/close() methods */
 114         alias_n_tty_open = pps_ldisc_ops.open;
 115         alias_n_tty_close = pps_ldisc_ops.close;
 116
 117         /* Init PPS_TTY data */
 118         pps_ldisc_ops.owner = THIS_MODULE;
 119         pps_ldisc_ops.magic = PPS_TTY_MAGIC;
 120         pps_ldisc_ops.name = "pps_tty";
 121         pps_ldisc_ops.dcd_change = pps_tty_dcd_change;
 122         pps_ldisc_ops.open = pps_tty_open;
 123         pps_ldisc_ops.close = pps_tty_close;
 124
 125         err = tty_register_ldisc(N_PPS, &pps_ldisc_ops);
 126         if (err)
 127                 pr_err("can't register PPS line discipline\n");
 128         else
 129                 pr_info("PPS line discipline registered\n");
 130
 131         return err;
 132 }
 133
 134 static void __exit pps_tty_cleanup(void)
 135 {
 136         int err;
 137
 138         err = tty_unregister_ldisc(N_PPS);
 139         if (err)
 140                 pr_err("can't unregister PPS line discipline\n");
 141         else
 142                 pr_info("PPS line discipline removed\n");
 143 }
 144
 145 module_init(pps_tty_init);
 146 module_exit(pps_tty_cleanup);
 147
 148 MODULE_ALIAS_LDISC(N_PPS);
 149 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
 150 MODULE_DESCRIPTION("PPS TTY device driver");
 151 MODULE_LICENSE("GPL");