1 // SPDX-License-Identifier: GPL-2.0-only
2 /* Counter - example userspace application
3  *
4  * The userspace application opens /dev/counter0, configures the
5  * COUNTER_EVENT_INDEX event channel 0 to gather Count 0 count and Count
6  * 1 count, and prints out the data as it becomes available on the
7  * character device node.
8  *
9  * Copyright (C) 2021 William Breathitt Gray
10  */
11 #include <errno.h>
12 #include <fcntl.h>
13 #include <linux/counter.h>
14 #include <stdio.h>
15 #include <string.h>
16 #include <sys/ioctl.h>
17 #include <unistd.h>
18 
19 static struct counter_watch watches[2] = {
20 	{
21 		/* Component data: Count 0 count */
22 		.component.type = COUNTER_COMPONENT_COUNT,
23 		.component.scope = COUNTER_SCOPE_COUNT,
24 		.component.parent = 0,
25 		/* Event type: Index */
26 		.event = COUNTER_EVENT_INDEX,
27 		/* Device event channel 0 */
28 		.channel = 0,
29 	},
30 	{
31 		/* Component data: Count 1 count */
32 		.component.type = COUNTER_COMPONENT_COUNT,
33 		.component.scope = COUNTER_SCOPE_COUNT,
34 		.component.parent = 1,
35 		/* Event type: Index */
36 		.event = COUNTER_EVENT_INDEX,
37 		/* Device event channel 0 */
38 		.channel = 0,
39 	},
40 };
41 
main(void)42 int main(void)
43 {
44 	int fd;
45 	int ret;
46 	int i;
47 	struct counter_event event_data[2];
48 
49 	fd = open("/dev/counter0", O_RDWR);
50 	if (fd == -1) {
51 		perror("Unable to open /dev/counter0");
52 		return 1;
53 	}
54 
55 	for (i = 0; i < 2; i++) {
56 		ret = ioctl(fd, COUNTER_ADD_WATCH_IOCTL, watches + i);
57 		if (ret == -1) {
58 			fprintf(stderr, "Error adding watches[%d]: %s\n", i,
59 				strerror(errno));
60 			return 1;
61 		}
62 	}
63 	ret = ioctl(fd, COUNTER_ENABLE_EVENTS_IOCTL);
64 	if (ret == -1) {
65 		perror("Error enabling events");
66 		return 1;
67 	}
68 
69 	for (;;) {
70 		ret = read(fd, event_data, sizeof(event_data));
71 		if (ret == -1) {
72 			perror("Failed to read event data");
73 			return 1;
74 		}
75 
76 		if (ret != sizeof(event_data)) {
77 			fprintf(stderr, "Failed to read event data\n");
78 			return -EIO;
79 		}
80 
81 		printf("Timestamp 0: %llu\tCount 0: %llu\n"
82 		       "Error Message 0: %s\n"
83 		       "Timestamp 1: %llu\tCount 1: %llu\n"
84 		       "Error Message 1: %s\n",
85 		       event_data[0].timestamp, event_data[0].value,
86 		       strerror(event_data[0].status),
87 		       event_data[1].timestamp, event_data[1].value,
88 		       strerror(event_data[1].status));
89 	}
90 
91 	return 0;
92 }
93