pps-ldisc.c
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/*
* pps-ldisc.c -- PPS line discipline
*
*
* Copyright (C) 2008 Rodolfo Giometti <giometti@linux.it>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/serial_core.h>
#include <linux/tty.h>
#include <linux/pps_kernel.h>
#include <linux/bug.h>
#define PPS_TTY_MAGIC 0x0001
static void pps_tty_dcd_change(struct tty_struct *tty, unsigned int status)
{
struct pps_device *pps;
struct pps_event_time ts;
pps_get_ts(&ts);
pps = pps_lookup_dev(tty);
/*
* This should never fail, but the ldisc locking is very
* convoluted, so don't crash just in case.
*/
if (WARN_ON_ONCE(pps == NULL))
return;
/* Now do the PPS event report */
pps_event(pps, &ts, status ? PPS_CAPTUREASSERT :
PPS_CAPTURECLEAR, NULL);
dev_dbg(pps->dev, "PPS %s at %lu\n",
status ? "assert" : "clear", jiffies);
}
static int (*alias_n_tty_open)(struct tty_struct *tty);
static int pps_tty_open(struct tty_struct *tty)
{
struct pps_source_info info;
struct tty_driver *drv = tty->driver;
int index = tty->index + drv->name_base;
struct pps_device *pps;
int ret;
info.owner = THIS_MODULE;
info.dev = NULL;
snprintf(info.name, PPS_MAX_NAME_LEN, "%s%d", drv->driver_name, index);
snprintf(info.path, PPS_MAX_NAME_LEN, "/dev/%s%d", drv->name, index);
info.mode = PPS_CAPTUREBOTH | \
PPS_OFFSETASSERT | PPS_OFFSETCLEAR | \
PPS_CANWAIT | PPS_TSFMT_TSPEC;
pps = pps_register_source(&info, PPS_CAPTUREBOTH | \
PPS_OFFSETASSERT | PPS_OFFSETCLEAR);
if (pps == NULL) {
pr_err("cannot register PPS source \"%s\"\n", info.path);
return -ENOMEM;
}
pps->lookup_cookie = tty;
/* Now open the base class N_TTY ldisc */
ret = alias_n_tty_open(tty);
if (ret < 0) {
pr_err("cannot open tty ldisc \"%s\"\n", info.path);
goto err_unregister;
}
dev_info(pps->dev, "source \"%s\" added\n", info.path);
return 0;
err_unregister:
pps_unregister_source(pps);
return ret;
}
static void (*alias_n_tty_close)(struct tty_struct *tty);
static void pps_tty_close(struct tty_struct *tty)
{
struct pps_device *pps = pps_lookup_dev(tty);
alias_n_tty_close(tty);
if (WARN_ON(!pps))
return;
dev_info(pps->dev, "removed\n");
pps_unregister_source(pps);
}
static struct tty_ldisc_ops pps_ldisc_ops;
/*
* Module stuff
*/
static int __init pps_tty_init(void)
{
int err;
/* Inherit the N_TTY's ops */
n_tty_inherit_ops(&pps_ldisc_ops);
/* Save N_TTY's open()/close() methods */
alias_n_tty_open = pps_ldisc_ops.open;
alias_n_tty_close = pps_ldisc_ops.close;
/* Init PPS_TTY data */
pps_ldisc_ops.owner = THIS_MODULE;
pps_ldisc_ops.magic = PPS_TTY_MAGIC;
pps_ldisc_ops.name = "pps_tty";
pps_ldisc_ops.dcd_change = pps_tty_dcd_change;
pps_ldisc_ops.open = pps_tty_open;
pps_ldisc_ops.close = pps_tty_close;
err = tty_register_ldisc(N_PPS, &pps_ldisc_ops);
if (err)
pr_err("can't register PPS line discipline\n");
else
pr_info("PPS line discipline registered\n");
return err;
}
static void __exit pps_tty_cleanup(void)
{
int err;
err = tty_unregister_ldisc(N_PPS);
if (err)
pr_err("can't unregister PPS line discipline\n");
else
pr_info("PPS line discipline removed\n");
}
module_init(pps_tty_init);
module_exit(pps_tty_cleanup);
MODULE_ALIAS_LDISC(N_PPS);
MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
MODULE_DESCRIPTION("PPS TTY device driver");
MODULE_LICENSE("GPL");