blob: 64642ccfe442c499fb4b6fb2432f1b9bee336915 [file] [log] [blame]
Jacek Anaszewskiae347322017-01-29 12:52:31 +01001/*
2 * led_hw_brightness_mon.c
3 *
4 * This program monitors LED brightness level changes having its origin
5 * in hardware/firmware, i.e. outside of kernel control.
6 * A timestamp and brightness value is printed each time the brightness changes.
7 *
8 * Usage: led_hw_brightness_mon <device-name>
9 *
10 * <device-name> is the name of the LED class device to be monitored. Pressing
11 * CTRL+C will exit.
12 */
13
14#include <errno.h>
15#include <fcntl.h>
16#include <poll.h>
17#include <stdio.h>
18#include <stdlib.h>
19#include <string.h>
20#include <time.h>
21#include <unistd.h>
22
23#include <linux/uleds.h>
24
25int main(int argc, char const *argv[])
26{
27 int fd, ret;
28 char brightness_file_path[LED_MAX_NAME_SIZE + 11];
29 struct pollfd pollfd;
30 struct timespec ts;
31 char buf[11];
32
33 if (argc != 2) {
34 fprintf(stderr, "Requires <device-name> argument\n");
35 return 1;
36 }
37
38 snprintf(brightness_file_path, LED_MAX_NAME_SIZE,
39 "/sys/class/leds/%s/brightness_hw_changed", argv[1]);
40
41 fd = open(brightness_file_path, O_RDONLY);
42 if (fd == -1) {
43 printf("Failed to open %s file\n", brightness_file_path);
44 return 1;
45 }
46
47 /*
48 * read may fail if no hw brightness change has occurred so far,
49 * but it is required to avoid spurious poll notifications in
50 * the opposite case.
51 */
52 read(fd, buf, sizeof(buf));
53
54 pollfd.fd = fd;
55 pollfd.events = POLLPRI;
56
57 while (1) {
58 ret = poll(&pollfd, 1, -1);
59 if (ret == -1) {
60 printf("Failed to poll %s file (%d)\n",
61 brightness_file_path, ret);
62 ret = 1;
63 break;
64 }
65
66 clock_gettime(CLOCK_MONOTONIC, &ts);
67
68 ret = read(fd, buf, sizeof(buf));
69 if (ret < 0)
70 break;
71
72 ret = lseek(pollfd.fd, 0, SEEK_SET);
73 if (ret < 0) {
74 printf("lseek failed (%d)\n", ret);
75 break;
76 }
77
78 printf("[%ld.%09ld] %d\n", ts.tv_sec, ts.tv_nsec, atoi(buf));
79 }
80
81 close(fd);
82
83 return ret;
84}