LXR linux/tools/leds/uledmon.c

   1/*
   2 * uledmon.c
   3 *
   4 * This program creates a new userspace LED class device and monitors it. A
   5 * timestamp and brightness value is printed each time the brightness changes.
   6 *
   7 * Usage: uledmon <device-name>
   8 *
   9 * <device-name> is the name of the LED class device to be created. Pressing
  10 * CTRL+C will exit.
  11 */
  12
  13#include <fcntl.h>
  14#include <stdio.h>
  15#include <string.h>
  16#include <time.h>
  17#include <unistd.h>
  18
  19#include <linux/uleds.h>
  20
  21int main(int argc, char const *argv[])
  22{
  23        struct uleds_user_dev uleds_dev;
  24        int fd, ret;
  25        int brightness;
  26        struct timespec ts;
  27
  28        if (argc != 2) {
  29                fprintf(stderr, "Requires <device-name> argument\n");
  30                return 1;
  31        }
  32
  33        strncpy(uleds_dev.name, argv[1], LED_MAX_NAME_SIZE);
  34        uleds_dev.max_brightness = 100;
  35
  36        fd = open("/dev/uleds", O_RDWR);
  37        if (fd == -1) {
  38                perror("Failed to open /dev/uleds");
  39                return 1;
  40        }
  41
  42        ret = write(fd, &uleds_dev, sizeof(uleds_dev));
  43        if (ret == -1) {
  44                perror("Failed to write to /dev/uleds");
  45                close(fd);
  46                return 1;
  47        }
  48
  49        while (1) {
  50                ret = read(fd, &brightness, sizeof(brightness));
  51                if (ret == -1) {
  52                        perror("Failed to read from /dev/uleds");
  53                        close(fd);
  54                        return 1;
  55                }
  56                clock_gettime(CLOCK_MONOTONIC, &ts);
  57                printf("[%ld.%09ld] %u\n", ts.tv_sec, ts.tv_nsec, brightness);
  58        }
  59
  60        close(fd);
  61
  62        return 0;
  63}
  64