150 lines
3.3 KiB
C
150 lines
3.3 KiB
C
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// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* pps-ldisc.c -- PPS line discipline
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*
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* Copyright (C) 2008 Rodolfo Giometti <giometti@linux.it>
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/module.h>
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#include <linux/serial_core.h>
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#include <linux/tty.h>
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#include <linux/pps_kernel.h>
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#include <linux/bug.h>
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#define PPS_TTY_MAGIC 0x0001
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static void pps_tty_dcd_change(struct tty_struct *tty, unsigned int status)
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{
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struct pps_device *pps;
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struct pps_event_time ts;
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pps_get_ts(&ts);
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pps = pps_lookup_dev(tty);
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/*
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* This should never fail, but the ldisc locking is very
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* convoluted, so don't crash just in case.
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*/
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if (WARN_ON_ONCE(pps == NULL))
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return;
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/* Now do the PPS event report */
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pps_event(pps, &ts, status ? PPS_CAPTUREASSERT :
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PPS_CAPTURECLEAR, NULL);
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dev_dbg(pps->dev, "PPS %s at %lu\n",
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status ? "assert" : "clear", jiffies);
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}
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static int (*alias_n_tty_open)(struct tty_struct *tty);
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static int pps_tty_open(struct tty_struct *tty)
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{
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struct pps_source_info info;
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struct tty_driver *drv = tty->driver;
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int index = tty->index + drv->name_base;
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struct pps_device *pps;
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int ret;
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info.owner = THIS_MODULE;
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info.dev = NULL;
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snprintf(info.name, PPS_MAX_NAME_LEN, "%s%d", drv->driver_name, index);
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snprintf(info.path, PPS_MAX_NAME_LEN, "/dev/%s%d", drv->name, index);
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info.mode = PPS_CAPTUREBOTH | \
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PPS_OFFSETASSERT | PPS_OFFSETCLEAR | \
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PPS_CANWAIT | PPS_TSFMT_TSPEC;
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pps = pps_register_source(&info, PPS_CAPTUREBOTH | \
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PPS_OFFSETASSERT | PPS_OFFSETCLEAR);
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if (IS_ERR(pps)) {
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pr_err("cannot register PPS source \"%s\"\n", info.path);
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return PTR_ERR(pps);
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}
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pps->lookup_cookie = tty;
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/* Now open the base class N_TTY ldisc */
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ret = alias_n_tty_open(tty);
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if (ret < 0) {
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pr_err("cannot open tty ldisc \"%s\"\n", info.path);
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goto err_unregister;
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}
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dev_info(pps->dev, "source \"%s\" added\n", info.path);
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return 0;
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err_unregister:
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pps_unregister_source(pps);
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return ret;
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}
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static void (*alias_n_tty_close)(struct tty_struct *tty);
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static void pps_tty_close(struct tty_struct *tty)
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{
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struct pps_device *pps = pps_lookup_dev(tty);
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alias_n_tty_close(tty);
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if (WARN_ON(!pps))
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return;
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dev_info(pps->dev, "removed\n");
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pps_unregister_source(pps);
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}
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static struct tty_ldisc_ops pps_ldisc_ops;
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/*
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* Module stuff
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*/
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static int __init pps_tty_init(void)
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{
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int err;
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/* Inherit the N_TTY's ops */
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n_tty_inherit_ops(&pps_ldisc_ops);
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/* Save N_TTY's open()/close() methods */
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alias_n_tty_open = pps_ldisc_ops.open;
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alias_n_tty_close = pps_ldisc_ops.close;
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/* Init PPS_TTY data */
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pps_ldisc_ops.owner = THIS_MODULE;
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pps_ldisc_ops.magic = PPS_TTY_MAGIC;
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pps_ldisc_ops.name = "pps_tty";
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pps_ldisc_ops.dcd_change = pps_tty_dcd_change;
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pps_ldisc_ops.open = pps_tty_open;
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pps_ldisc_ops.close = pps_tty_close;
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err = tty_register_ldisc(N_PPS, &pps_ldisc_ops);
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if (err)
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pr_err("can't register PPS line discipline\n");
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else
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pr_info("PPS line discipline registered\n");
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return err;
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}
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static void __exit pps_tty_cleanup(void)
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{
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int err;
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err = tty_unregister_ldisc(N_PPS);
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if (err)
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pr_err("can't unregister PPS line discipline\n");
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else
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pr_info("PPS line discipline removed\n");
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}
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module_init(pps_tty_init);
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module_exit(pps_tty_cleanup);
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MODULE_ALIAS_LDISC(N_PPS);
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MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
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MODULE_DESCRIPTION("PPS TTY device driver");
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MODULE_LICENSE("GPL");
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