1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * uledmon.c
4 *
5 * This program creates a new userspace LED class device and monitors it. A
6 * timestamp and brightness value is printed each time the brightness changes.
7 *
8 * Usage: uledmon <device-name>
9 *
10 * <device-name> is the name of the LED class device to be created. Pressing
11 * CTRL+C will exit.
12 */
13
14 #include <fcntl.h>
15 #include <stdio.h>
16 #include <string.h>
17 #include <time.h>
18 #include <unistd.h>
19
20 #include <linux/uleds.h>
21
main(int argc,char const * argv[])22 int main(int argc, char const *argv[])
23 {
24 struct uleds_user_dev uleds_dev;
25 int fd, ret;
26 int brightness;
27 struct timespec ts;
28
29 if (argc != 2) {
30 fprintf(stderr, "Requires <device-name> argument\n");
31 return 1;
32 }
33
34 strncpy(uleds_dev.name, argv[1], LED_MAX_NAME_SIZE);
35 uleds_dev.max_brightness = 100;
36
37 fd = open("/dev/uleds", O_RDWR);
38 if (fd == -1) {
39 perror("Failed to open /dev/uleds");
40 return 1;
41 }
42
43 ret = write(fd, &uleds_dev, sizeof(uleds_dev));
44 if (ret == -1) {
45 perror("Failed to write to /dev/uleds");
46 close(fd);
47 return 1;
48 }
49
50 while (1) {
51 ret = read(fd, &brightness, sizeof(brightness));
52 if (ret == -1) {
53 perror("Failed to read from /dev/uleds");
54 close(fd);
55 return 1;
56 }
57 clock_gettime(CLOCK_MONOTONIC, &ts);
58 printf("[%ld.%09ld] %u\n", ts.tv_sec, ts.tv_nsec, brightness);
59 }
60
61 close(fd);
62
63 return 0;
64 }
65