LXR linux/tools/leds/uledmon.c

   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}
  65