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