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
  21 int 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 }