1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * pps-ldisc.c -- PPS line discipline 4 * 5 * Copyright (C) 2008 Rodolfo Giometti <giometti@linux.it> 6 */ 7 8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 9 10 #include <linux/module.h> 11 #include <linux/serial_core.h> 12 #include <linux/tty.h> 13 #include <linux/pps_kernel.h> 14 #include <linux/bug.h> 15 16 static void pps_tty_dcd_change(struct tty_struct *tty, unsigned int status) 17 { 18 struct pps_device *pps; 19 struct pps_event_time ts; 20 21 pps_get_ts(&ts); 22 23 pps = pps_lookup_dev(tty); 24 /* 25 * This should never fail, but the ldisc locking is very 26 * convoluted, so don't crash just in case. 27 */ 28 if (WARN_ON_ONCE(pps == NULL)) 29 return; 30 31 /* Now do the PPS event report */ 32 pps_event(pps, &ts, status ? PPS_CAPTUREASSERT : 33 PPS_CAPTURECLEAR, NULL); 34 35 dev_dbg(pps->dev, "PPS %s at %lu\n", 36 status ? "assert" : "clear", jiffies); 37 } 38 39 static int (*alias_n_tty_open)(struct tty_struct *tty); 40 41 static int pps_tty_open(struct tty_struct *tty) 42 { 43 struct pps_source_info info; 44 struct tty_driver *drv = tty->driver; 45 int index = tty->index + drv->name_base; 46 struct pps_device *pps; 47 int ret; 48 49 info.owner = THIS_MODULE; 50 info.dev = NULL; 51 snprintf(info.name, PPS_MAX_NAME_LEN, "%s%d", drv->driver_name, index); 52 snprintf(info.path, PPS_MAX_NAME_LEN, "/dev/%s%d", drv->name, index); 53 info.mode = PPS_CAPTUREBOTH | \ 54 PPS_OFFSETASSERT | PPS_OFFSETCLEAR | \ 55 PPS_CANWAIT | PPS_TSFMT_TSPEC; 56 57 pps = pps_register_source(&info, PPS_CAPTUREBOTH | \ 58 PPS_OFFSETASSERT | PPS_OFFSETCLEAR); 59 if (IS_ERR(pps)) { 60 pr_err("cannot register PPS source \"%s\"\n", info.path); 61 return PTR_ERR(pps); 62 } 63 pps->lookup_cookie = tty; 64 65 /* Now open the base class N_TTY ldisc */ 66 ret = alias_n_tty_open(tty); 67 if (ret < 0) { 68 pr_err("cannot open tty ldisc \"%s\"\n", info.path); 69 goto err_unregister; 70 } 71 72 dev_info(pps->dev, "source \"%s\" added\n", info.path); 73 74 return 0; 75 76 err_unregister: 77 pps_unregister_source(pps); 78 return ret; 79 } 80 81 static void (*alias_n_tty_close)(struct tty_struct *tty); 82 83 static void pps_tty_close(struct tty_struct *tty) 84 { 85 struct pps_device *pps = pps_lookup_dev(tty); 86 87 alias_n_tty_close(tty); 88 89 if (WARN_ON(!pps)) 90 return; 91 92 dev_info(pps->dev, "removed\n"); 93 pps_unregister_source(pps); 94 } 95 96 static struct tty_ldisc_ops pps_ldisc_ops; 97 98 /* 99 * Module stuff 100 */ 101 102 static int __init pps_tty_init(void) 103 { 104 int err; 105 106 /* Inherit the N_TTY's ops */ 107 n_tty_inherit_ops(&pps_ldisc_ops); 108 109 /* Save N_TTY's open()/close() methods */ 110 alias_n_tty_open = pps_ldisc_ops.open; 111 alias_n_tty_close = pps_ldisc_ops.close; 112 113 /* Init PPS_TTY data */ 114 pps_ldisc_ops.owner = THIS_MODULE; 115 pps_ldisc_ops.num = N_PPS; 116 pps_ldisc_ops.name = "pps_tty"; 117 pps_ldisc_ops.dcd_change = pps_tty_dcd_change; 118 pps_ldisc_ops.open = pps_tty_open; 119 pps_ldisc_ops.close = pps_tty_close; 120 121 err = tty_register_ldisc(&pps_ldisc_ops); 122 if (err) 123 pr_err("can't register PPS line discipline\n"); 124 else 125 pr_info("PPS line discipline registered\n"); 126 127 return err; 128 } 129 130 static void __exit pps_tty_cleanup(void) 131 { 132 tty_unregister_ldisc(&pps_ldisc_ops); 133 } 134 135 module_init(pps_tty_init); 136 module_exit(pps_tty_cleanup); 137 138 MODULE_ALIAS_LDISC(N_PPS); 139 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>"); 140 MODULE_DESCRIPTION("PPS TTY device driver"); 141 MODULE_LICENSE("GPL"); 142