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#include <linux/bug.h>
  29
  30#define PPS_TTY_MAGIC           0x0001
  31
  32static 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
  55static int (*alias_n_tty_open)(struct tty_struct *tty);
  56
  57static 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
  92err_unregister:
  93        pps_unregister_source(pps);
  94        return ret;
  95}
  96
  97static void (*alias_n_tty_close)(struct tty_struct *tty);
  98
  99static 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
 112static struct tty_ldisc_ops pps_ldisc_ops;
 113
 114/*
 115 * Module stuff
 116 */
 117
 118static 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
 146static 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
 157module_init(pps_tty_init);
 158module_exit(pps_tty_cleanup);
 159
 160MODULE_ALIAS_LDISC(N_PPS);
 161MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
 162MODULE_DESCRIPTION("PPS TTY device driver");
 163MODULE_LICENSE("GPL");
 164