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 #define PPS_TTY_MAGIC 0x0001 17 18 static void pps_tty_dcd_change(struct tty_struct *tty, unsigned int status) 19 { 20 struct pps_device *pps; 21 struct pps_event_time ts; 22 23 pps_get_ts(&ts); 24 25 pps = pps_lookup_dev(tty); 26 /* 27 * This should never fail, but the ldisc locking is very 28 * convoluted, so don't crash just in case. 29 */ 30 if (WARN_ON_ONCE(pps == NULL)) 31 return; 32 33 /* Now do the PPS event report */ 34 pps_event(pps, &ts, status ? PPS_CAPTUREASSERT : 35 PPS_CAPTURECLEAR, NULL); 36 37 dev_dbg(pps->dev, "PPS %s at %lu\n", 38 status ? "assert" : "clear", jiffies); 39 } 40 41 static int (*alias_n_tty_open)(struct tty_struct *tty); 42 43 static int pps_tty_open(struct tty_struct *tty) 44 { 45 struct pps_source_info info; 46 struct tty_driver *drv = tty->driver; 47 int index = tty->index + drv->name_base; 48 struct pps_device *pps; 49 int ret; 50 51 info.owner = THIS_MODULE; 52 info.dev = NULL; 53 snprintf(info.name, PPS_MAX_NAME_LEN, "%s%d", drv->driver_name, index); 54 snprintf(info.path, PPS_MAX_NAME_LEN, "/dev/%s%d", drv->name, index); 55 info.mode = PPS_CAPTUREBOTH | \ 56 PPS_OFFSETASSERT | PPS_OFFSETCLEAR | \ 57 PPS_CANWAIT | PPS_TSFMT_TSPEC; 58 59 pps = pps_register_source(&info, PPS_CAPTUREBOTH | \ 60 PPS_OFFSETASSERT | PPS_OFFSETCLEAR); 61 if (IS_ERR(pps)) { 62 pr_err("cannot register PPS source \"%s\"\n", info.path); 63 return PTR_ERR(pps); 64 } 65 pps->lookup_cookie = tty; 66 67 /* Now open the base class N_TTY ldisc */ 68 ret = alias_n_tty_open(tty); 69 if (ret < 0) { 70 pr_err("cannot open tty ldisc \"%s\"\n", info.path); 71 goto err_unregister; 72 } 73 74 dev_info(pps->dev, "source \"%s\" added\n", info.path); 75 76 return 0; 77 78 err_unregister: 79 pps_unregister_source(pps); 80 return ret; 81 } 82 83 static void (*alias_n_tty_close)(struct tty_struct *tty); 84 85 static void pps_tty_close(struct tty_struct *tty) 86 { 87 struct pps_device *pps = pps_lookup_dev(tty); 88 89 alias_n_tty_close(tty); 90 91 if (WARN_ON(!pps)) 92 return; 93 94 dev_info(pps->dev, "removed\n"); 95 pps_unregister_source(pps); 96 } 97 98 static struct tty_ldisc_ops pps_ldisc_ops; 99 100 /* 101 * Module stuff 102 */ 103 104 static int __init pps_tty_init(void) 105 { 106 int err; 107 108 /* Inherit the N_TTY's ops */ 109 n_tty_inherit_ops(&pps_ldisc_ops); 110 111 /* Save N_TTY's open()/close() methods */ 112 alias_n_tty_open = pps_ldisc_ops.open; 113 alias_n_tty_close = pps_ldisc_ops.close; 114 115 /* Init PPS_TTY data */ 116 pps_ldisc_ops.owner = THIS_MODULE; 117 pps_ldisc_ops.magic = PPS_TTY_MAGIC; 118 pps_ldisc_ops.name = "pps_tty"; 119 pps_ldisc_ops.dcd_change = pps_tty_dcd_change; 120 pps_ldisc_ops.open = pps_tty_open; 121 pps_ldisc_ops.close = pps_tty_close; 122 123 err = tty_register_ldisc(N_PPS, &pps_ldisc_ops); 124 if (err) 125 pr_err("can't register PPS line discipline\n"); 126 else 127 pr_info("PPS line discipline registered\n"); 128 129 return err; 130 } 131 132 static void __exit pps_tty_cleanup(void) 133 { 134 int err; 135 136 err = tty_unregister_ldisc(N_PPS); 137 if (err) 138 pr_err("can't unregister PPS line discipline\n"); 139 else 140 pr_info("PPS line discipline removed\n"); 141 } 142 143 module_init(pps_tty_init); 144 module_exit(pps_tty_cleanup); 145 146 MODULE_ALIAS_LDISC(N_PPS); 147 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>"); 148 MODULE_DESCRIPTION("PPS TTY device driver"); 149 MODULE_LICENSE("GPL"); 150