// SPDX-License-Identifier: GPL-2.0

  /*
   * uledmon.c
   *
   * This program creates a new userspace LED class device and monitors it. A
   * timestamp and brightness value is printed each time the brightness changes.
   *
   * Usage: uledmon <device-name>
   *
   * <device-name> is the name of the LED class device to be created. Pressing
   * CTRL+C will exit.
   */
  
  #include <fcntl.h>
  #include <stdio.h>
  #include <string.h>
  #include <time.h>
  #include <unistd.h>
  
  #include <linux/uleds.h>
  
  int main(int argc, char const *argv[])
  {
  	struct uleds_user_dev uleds_dev;
  	int fd, ret;
  	int brightness;
  	struct timespec ts;
  
  	if (argc != 2) {
  		fprintf(stderr, "Requires <device-name> argument
  ");
  		return 1;
  	}
  
  	strncpy(uleds_dev.name, argv[1], LED_MAX_NAME_SIZE);
  	uleds_dev.max_brightness = 100;
  
  	fd = open("/dev/uleds", O_RDWR);
  	if (fd == -1) {
  		perror("Failed to open /dev/uleds");
  		return 1;
  	}
  
  	ret = write(fd, &uleds_dev, sizeof(uleds_dev));
  	if (ret == -1) {
  		perror("Failed to write to /dev/uleds");
  		close(fd);
  		return 1;
  	}
  
  	while (1) {
  		ret = read(fd, &brightness, sizeof(brightness));
  		if (ret == -1) {
  			perror("Failed to read from /dev/uleds");
  			close(fd);
  			return 1;
  		}
  		clock_gettime(CLOCK_MONOTONIC, &ts);
  		printf("[%ld.%09ld] %u
  ", ts.tv_sec, ts.tv_nsec, brightness);
  	}
  
  	close(fd);
  
  	return 0;
  }