1*4882a593Smuzhiyun // SPDX-License-Identifier: GPL-2.0
2*4882a593Smuzhiyun /*
3*4882a593Smuzhiyun * led_hw_brightness_mon.c
4*4882a593Smuzhiyun *
5*4882a593Smuzhiyun * This program monitors LED brightness level changes having its origin
6*4882a593Smuzhiyun * in hardware/firmware, i.e. outside of kernel control.
7*4882a593Smuzhiyun * A timestamp and brightness value is printed each time the brightness changes.
8*4882a593Smuzhiyun *
9*4882a593Smuzhiyun * Usage: led_hw_brightness_mon <device-name>
10*4882a593Smuzhiyun *
11*4882a593Smuzhiyun * <device-name> is the name of the LED class device to be monitored. Pressing
12*4882a593Smuzhiyun * CTRL+C will exit.
13*4882a593Smuzhiyun */
14*4882a593Smuzhiyun
15*4882a593Smuzhiyun #include <errno.h>
16*4882a593Smuzhiyun #include <fcntl.h>
17*4882a593Smuzhiyun #include <poll.h>
18*4882a593Smuzhiyun #include <stdio.h>
19*4882a593Smuzhiyun #include <stdlib.h>
20*4882a593Smuzhiyun #include <string.h>
21*4882a593Smuzhiyun #include <time.h>
22*4882a593Smuzhiyun #include <unistd.h>
23*4882a593Smuzhiyun
24*4882a593Smuzhiyun #include <linux/uleds.h>
25*4882a593Smuzhiyun
main(int argc,char const * argv[])26*4882a593Smuzhiyun int main(int argc, char const *argv[])
27*4882a593Smuzhiyun {
28*4882a593Smuzhiyun int fd, ret;
29*4882a593Smuzhiyun char brightness_file_path[LED_MAX_NAME_SIZE + 11];
30*4882a593Smuzhiyun struct pollfd pollfd;
31*4882a593Smuzhiyun struct timespec ts;
32*4882a593Smuzhiyun char buf[11];
33*4882a593Smuzhiyun
34*4882a593Smuzhiyun if (argc != 2) {
35*4882a593Smuzhiyun fprintf(stderr, "Requires <device-name> argument\n");
36*4882a593Smuzhiyun return 1;
37*4882a593Smuzhiyun }
38*4882a593Smuzhiyun
39*4882a593Smuzhiyun snprintf(brightness_file_path, LED_MAX_NAME_SIZE,
40*4882a593Smuzhiyun "/sys/class/leds/%s/brightness_hw_changed", argv[1]);
41*4882a593Smuzhiyun
42*4882a593Smuzhiyun fd = open(brightness_file_path, O_RDONLY);
43*4882a593Smuzhiyun if (fd == -1) {
44*4882a593Smuzhiyun printf("Failed to open %s file\n", brightness_file_path);
45*4882a593Smuzhiyun return 1;
46*4882a593Smuzhiyun }
47*4882a593Smuzhiyun
48*4882a593Smuzhiyun /*
49*4882a593Smuzhiyun * read may fail if no hw brightness change has occurred so far,
50*4882a593Smuzhiyun * but it is required to avoid spurious poll notifications in
51*4882a593Smuzhiyun * the opposite case.
52*4882a593Smuzhiyun */
53*4882a593Smuzhiyun read(fd, buf, sizeof(buf));
54*4882a593Smuzhiyun
55*4882a593Smuzhiyun pollfd.fd = fd;
56*4882a593Smuzhiyun pollfd.events = POLLPRI;
57*4882a593Smuzhiyun
58*4882a593Smuzhiyun while (1) {
59*4882a593Smuzhiyun ret = poll(&pollfd, 1, -1);
60*4882a593Smuzhiyun if (ret == -1) {
61*4882a593Smuzhiyun printf("Failed to poll %s file (%d)\n",
62*4882a593Smuzhiyun brightness_file_path, ret);
63*4882a593Smuzhiyun ret = 1;
64*4882a593Smuzhiyun break;
65*4882a593Smuzhiyun }
66*4882a593Smuzhiyun
67*4882a593Smuzhiyun clock_gettime(CLOCK_MONOTONIC, &ts);
68*4882a593Smuzhiyun
69*4882a593Smuzhiyun ret = read(fd, buf, sizeof(buf));
70*4882a593Smuzhiyun if (ret < 0)
71*4882a593Smuzhiyun break;
72*4882a593Smuzhiyun
73*4882a593Smuzhiyun ret = lseek(pollfd.fd, 0, SEEK_SET);
74*4882a593Smuzhiyun if (ret < 0) {
75*4882a593Smuzhiyun printf("lseek failed (%d)\n", ret);
76*4882a593Smuzhiyun break;
77*4882a593Smuzhiyun }
78*4882a593Smuzhiyun
79*4882a593Smuzhiyun printf("[%ld.%09ld] %d\n", ts.tv_sec, ts.tv_nsec, atoi(buf));
80*4882a593Smuzhiyun }
81*4882a593Smuzhiyun
82*4882a593Smuzhiyun close(fd);
83*4882a593Smuzhiyun
84*4882a593Smuzhiyun return ret;
85*4882a593Smuzhiyun }
86