1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Simple heartbeat STM source driver
4 * Copyright (c) 2016, Intel Corporation.
5 *
6 * Heartbeat STM source will send repetitive messages over STM devices to a
7 * trace host.
8 */
9
10 #include <linux/kernel.h>
11 #include <linux/module.h>
12 #include <linux/hrtimer.h>
13 #include <linux/slab.h>
14 #include <linux/stm.h>
15
16 #define STM_HEARTBEAT_MAX 32
17
18 static int nr_devs = 4;
19 static int interval_ms = 10;
20
21 module_param(nr_devs, int, 0400);
22 module_param(interval_ms, int, 0600);
23
24 static struct stm_heartbeat {
25 struct stm_source_data data;
26 struct hrtimer hrtimer;
27 unsigned int active;
28 } stm_heartbeat[STM_HEARTBEAT_MAX];
29
30 static const char str[] = "heartbeat stm source driver is here to serve you";
31
stm_heartbeat_hrtimer_handler(struct hrtimer * hr)32 static enum hrtimer_restart stm_heartbeat_hrtimer_handler(struct hrtimer *hr)
33 {
34 struct stm_heartbeat *heartbeat = container_of(hr, struct stm_heartbeat,
35 hrtimer);
36
37 stm_source_write(&heartbeat->data, 0, str, sizeof str);
38 if (heartbeat->active)
39 hrtimer_forward_now(hr, ms_to_ktime(interval_ms));
40
41 return heartbeat->active ? HRTIMER_RESTART : HRTIMER_NORESTART;
42 }
43
stm_heartbeat_link(struct stm_source_data * data)44 static int stm_heartbeat_link(struct stm_source_data *data)
45 {
46 struct stm_heartbeat *heartbeat =
47 container_of(data, struct stm_heartbeat, data);
48
49 heartbeat->active = 1;
50 hrtimer_start(&heartbeat->hrtimer, ms_to_ktime(interval_ms),
51 HRTIMER_MODE_ABS);
52
53 return 0;
54 }
55
stm_heartbeat_unlink(struct stm_source_data * data)56 static void stm_heartbeat_unlink(struct stm_source_data *data)
57 {
58 struct stm_heartbeat *heartbeat =
59 container_of(data, struct stm_heartbeat, data);
60
61 heartbeat->active = 0;
62 hrtimer_cancel(&heartbeat->hrtimer);
63 }
64
stm_heartbeat_init(void)65 static int stm_heartbeat_init(void)
66 {
67 int i, ret;
68
69 if (nr_devs < 0 || nr_devs > STM_HEARTBEAT_MAX)
70 return -EINVAL;
71
72 for (i = 0; i < nr_devs; i++) {
73 stm_heartbeat[i].data.name =
74 kasprintf(GFP_KERNEL, "heartbeat.%d", i);
75 if (!stm_heartbeat[i].data.name) {
76 ret = -ENOMEM;
77 goto fail_unregister;
78 }
79
80 stm_heartbeat[i].data.nr_chans = 1;
81 stm_heartbeat[i].data.type = STM_USER;
82 stm_heartbeat[i].data.link = stm_heartbeat_link;
83 stm_heartbeat[i].data.unlink = stm_heartbeat_unlink;
84 hrtimer_setup(&stm_heartbeat[i].hrtimer, stm_heartbeat_hrtimer_handler,
85 CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
86
87 ret = stm_source_register_device(NULL, &stm_heartbeat[i].data);
88 if (ret)
89 goto fail_free;
90 }
91
92 return 0;
93
94 fail_unregister:
95 for (i--; i >= 0; i--) {
96 stm_source_unregister_device(&stm_heartbeat[i].data);
97 fail_free:
98 kfree(stm_heartbeat[i].data.name);
99 }
100
101 return ret;
102 }
103
stm_heartbeat_exit(void)104 static void stm_heartbeat_exit(void)
105 {
106 int i;
107
108 for (i = 0; i < nr_devs; i++) {
109 stm_source_unregister_device(&stm_heartbeat[i].data);
110 kfree(stm_heartbeat[i].data.name);
111 }
112 }
113
114 module_init(stm_heartbeat_init);
115 module_exit(stm_heartbeat_exit);
116
117 MODULE_LICENSE("GPL v2");
118 MODULE_DESCRIPTION("stm_heartbeat driver");
119 MODULE_AUTHOR("Alexander Shishkin <alexander.shishkin@linux.intel.com>");
120