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
pps_tty_dcd_change(struct tty_struct * tty,unsigned int status)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
pps_tty_open(struct tty_struct * tty)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
pps_tty_close(struct tty_struct * tty)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
pps_tty_init(void)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.name = "pps_tty";
116 pps_ldisc_ops.dcd_change = pps_tty_dcd_change;
117 pps_ldisc_ops.open = pps_tty_open;
118 pps_ldisc_ops.close = pps_tty_close;
119
120 err = tty_register_ldisc(N_PPS, &pps_ldisc_ops);
121 if (err)
122 pr_err("can't register PPS line discipline\n");
123 else
124 pr_info("PPS line discipline registered\n");
125
126 return err;
127 }
128
pps_tty_cleanup(void)129 static void __exit pps_tty_cleanup(void)
130 {
131 int err;
132
133 err = tty_unregister_ldisc(N_PPS);
134 if (err)
135 pr_err("can't unregister PPS line discipline\n");
136 else
137 pr_info("PPS line discipline removed\n");
138 }
139
140 module_init(pps_tty_init);
141 module_exit(pps_tty_cleanup);
142
143 MODULE_ALIAS_LDISC(N_PPS);
144 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
145 MODULE_DESCRIPTION("PPS TTY device driver");
146 MODULE_LICENSE("GPL");
147