LXR linux/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
  31static void pps_tty_dcd_change(struct tty_struct *tty, unsigned int status,
  32                                struct pps_event_time *ts)
  33{
  34        struct pps_device *pps = (struct pps_device *)tty->disc_data;
  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
  46static int (*alias_n_tty_open)(struct tty_struct *tty);
  47
  48static 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        tty->disc_data = pps;
  71
  72        /* Should open N_TTY ldisc too */
  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
  83err_unregister:
  84        tty->disc_data = NULL;
  85        pps_unregister_source(pps);
  86        return ret;
  87}
  88
  89static void (*alias_n_tty_close)(struct tty_struct *tty);
  90
  91static void pps_tty_close(struct tty_struct *tty)
  92{
  93        struct pps_device *pps = (struct pps_device *)tty->disc_data;
  94
  95        alias_n_tty_close(tty);
  96
  97        tty->disc_data = NULL;
  98        dev_info(pps->dev, "removed\n");
  99        pps_unregister_source(pps);
 100}
 101
 102static struct tty_ldisc_ops pps_ldisc_ops;
 103
 104/*
 105 * Module stuff
 106 */
 107
 108static int __init pps_tty_init(void)
 109{
 110        int err;
 111
 112        /* Inherit the N_TTY's ops */
 113        n_tty_inherit_ops(&pps_ldisc_ops);
 114
 115        /* Save N_TTY's open()/close() methods */
 116        alias_n_tty_open = pps_ldisc_ops.open;
 117        alias_n_tty_close = pps_ldisc_ops.close;
 118
 119        /* Init PPS_TTY data */
 120        pps_ldisc_ops.owner = THIS_MODULE;
 121        pps_ldisc_ops.magic = PPS_TTY_MAGIC;
 122        pps_ldisc_ops.name = "pps_tty";
 123        pps_ldisc_ops.dcd_change = pps_tty_dcd_change;
 124        pps_ldisc_ops.open = pps_tty_open;
 125        pps_ldisc_ops.close = pps_tty_close;
 126
 127        err = tty_register_ldisc(N_PPS, &pps_ldisc_ops);
 128        if (err)
 129                pr_err("can't register PPS line discipline\n");
 130        else
 131                pr_info("PPS line discipline registered\n");
 132
 133        return err;
 134}
 135
 136static void __exit pps_tty_cleanup(void)
 137{
 138        int err;
 139
 140        err = tty_unregister_ldisc(N_PPS);
 141        if (err)
 142                pr_err("can't unregister PPS line discipline\n");
 143        else
 144                pr_info("PPS line discipline removed\n");
 145}
 146
 147module_init(pps_tty_init);
 148module_exit(pps_tty_cleanup);
 149
 150MODULE_ALIAS_LDISC(N_PPS);
 151MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
 152MODULE_DESCRIPTION("PPS TTY device driver");
 153MODULE_LICENSE("GPL");
 154