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, bool active) |
17 | { |
18 | struct pps_device *pps; |
19 | struct pps_event_time ts; |
20 | |
21 | pps_get_ts(ts: &ts); |
22 | |
23 | pps = pps_lookup_dev(cookie: 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: &ts, event: active ? PPS_CAPTUREASSERT : |
33 | PPS_CAPTURECLEAR, NULL); |
34 | |
35 | dev_dbg(pps->dev, "PPS %s at %lu\n" , |
36 | active ? "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(buf: info.name, PPS_MAX_NAME_LEN, fmt: "%s%d" , drv->driver_name, index); |
52 | snprintf(buf: info.path, PPS_MAX_NAME_LEN, fmt: "/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: &info, PPS_CAPTUREBOTH | \ |
58 | PPS_OFFSETASSERT | PPS_OFFSETCLEAR); |
59 | if (IS_ERR(ptr: pps)) { |
60 | pr_err("cannot register PPS source \"%s\"\n" , info.path); |
61 | return PTR_ERR(ptr: 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(cookie: 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(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(new_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(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 | |