1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * PPS dummy generator
4 *
5 * Copyright (C) 2024 Rodolfo Giometti <[email protected]>
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
16 static struct pps_gen_device *pps_gen;
17 static struct timer_list ktimer;
18
get_random_delay(void)19 static 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
pps_gen_ktimer_event(struct timer_list * unused)30 static 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
pps_gen_dummy_get_time(struct pps_gen_device * pps_gen,struct timespec64 * time)39 static 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
pps_gen_dummy_enable(struct pps_gen_device * pps_gen,bool enable)50 static 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 del_timer_sync(&ktimer);
56
57 return 0;
58 }
59
60 /*
61 * The PPS info struct
62 */
63
64 static 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
pps_gen_dummy_exit(void)74 static void __exit pps_gen_dummy_exit(void)
75 {
76 del_timer_sync(&ktimer);
77 pps_gen_unregister_source(pps_gen);
78 }
79
pps_gen_dummy_init(void)80 static 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
91 module_init(pps_gen_dummy_init);
92 module_exit(pps_gen_dummy_exit);
93
94 MODULE_AUTHOR("Rodolfo Giometti <[email protected]>");
95 MODULE_DESCRIPTION("LinuxPPS dummy generator");
96 MODULE_LICENSE("GPL");
97