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