pps_gen-dummy.c

 1// SPDX-License-Identifier: GPL-2.0-or-later
 2/*
 3 * PPS dummy generator
 4 *
 5 * Copyright (C) 2024 Rodolfo Giometti <giometti@enneenne.com>
 6 */
 7
 8#include <linux/kernel.h>
 9#include <linux/module.h>
10#include <linux/init.h>
11#include <linux/time.h>
12#include <linux/timer.h>
13#include <linux/random.h>
14#include <linux/pps_gen_kernel.h>
15
16static struct pps_gen_device *pps_gen;
17static struct timer_list ktimer;
18
19static unsigned int get_random_delay(void)
20{
21	unsigned int delay = get_random_u8() & 0x0f;
22
23	return (delay + 1) * HZ;
24}
25
26/*
27 * The kernel timer
28 */
29
30static void pps_gen_ktimer_event(struct timer_list *unused)
31{
32	pps_gen_event(pps_gen, PPS_GEN_EVENT_MISSEDPULSE, NULL);
33}
34
35/*
36 * PPS Generator methods
37 */
38
39static int pps_gen_dummy_get_time(struct pps_gen_device *pps_gen,
40					struct timespec64 *time)
41{
42	struct system_time_snapshot snap;
43
44	ktime_get_snapshot(&snap);
45	*time = ktime_to_timespec64(snap.real);
46
47	return 0;
48}
49
50static int pps_gen_dummy_enable(struct pps_gen_device *pps_gen, bool enable)
51{
52	if (enable)
53		mod_timer(&ktimer, jiffies + get_random_delay());
54	else
55		timer_delete_sync(&ktimer);
56
57	return 0;
58}
59
60/*
61 * The PPS info struct
62 */
63
64static const struct pps_gen_source_info pps_gen_dummy_info = {
65	.use_system_clock	= true,
66	.get_time		= pps_gen_dummy_get_time,
67	.enable			= pps_gen_dummy_enable,
68};
69
70/*
71 * Module staff
72 */
73
74static void __exit pps_gen_dummy_exit(void)
75{
76	timer_delete_sync(&ktimer);
77	pps_gen_unregister_source(pps_gen);
78}
79
80static int __init pps_gen_dummy_init(void)
81{
82	pps_gen = pps_gen_register_source(&pps_gen_dummy_info);
83	if (IS_ERR(pps_gen))
84		return PTR_ERR(pps_gen);
85
86	timer_setup(&ktimer, pps_gen_ktimer_event, 0);
87
88	return 0;
89}
90
91module_init(pps_gen_dummy_init);
92module_exit(pps_gen_dummy_exit);
93
94MODULE_AUTHOR("Rodolfo Giometti <giometti@enneenne.com>");
95MODULE_DESCRIPTION("LinuxPPS dummy generator");
96MODULE_LICENSE("GPL");