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
22int 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}