tools/leds: Add led_hw_brightness_mon program

CC = $(CROSS_COMPILE)gcc

CFLAGS = -Wall -Wextra -g -I../../include/uapi

all: uledmon

all: uledmon led_hw_brightness_mon

%: %.c

	$(CC) $(CFLAGS) -o $@ $^

clean:

	$(RM) uledmon

	$(RM) uledmon led_hw_brightness_mon

.PHONY: all clean

/*

 * led_hw_brightness_mon.c

 *

 * This program monitors LED brightness level changes having its origin

 * in hardware/firmware, i.e. outside of kernel control.

 * A timestamp and brightness value is printed each time the brightness changes.

 *

 * Usage: led_hw_brightness_mon <device-name>

 *

 * <device-name> is the name of the LED class device to be monitored. Pressing

 * CTRL+C will exit.

 */

#include <errno.h>

#include <fcntl.h>

#include <poll.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <time.h>

#include <unistd.h>

#include <linux/uleds.h>

int main(int argc, char const *argv[])

{

	int fd, ret;

	char brightness_file_path[LED_MAX_NAME_SIZE + 11];

	struct pollfd pollfd;

	struct timespec ts;

	char buf[11];

	if (argc != 2) {

		fprintf(stderr, "Requires <device-name> argument\n");

		return 1;

	}

	snprintf(brightness_file_path, LED_MAX_NAME_SIZE,

		 "/sys/class/leds/%s/brightness_hw_changed", argv[1]);

	fd = open(brightness_file_path, O_RDONLY);

	if (fd == -1) {

		printf("Failed to open %s file\n", brightness_file_path);

		return 1;

	}

	/*

	 * read may fail if no hw brightness change has occurred so far,

	 * but it is required to avoid spurious poll notifications in

	 * the opposite case.

	 */

	read(fd, buf, sizeof(buf));

	pollfd.fd = fd;

	pollfd.events = POLLPRI;

	while (1) {

		ret = poll(&pollfd, 1, -1);

		if (ret == -1) {

			printf("Failed to poll %s file (%d)\n",

				brightness_file_path, ret);

			ret = 1;

			break;

		}

		clock_gettime(CLOCK_MONOTONIC, &ts);

		ret = read(fd, buf, sizeof(buf));

		if (ret < 0)

			break;

		ret = lseek(pollfd.fd, 0, SEEK_SET);

		if (ret < 0) {

			printf("lseek failed (%d)\n", ret);

			break;

		}

		printf("[%ld.%09ld] %d\n", ts.tv_sec, ts.tv_nsec, atoi(buf));

	}

	close(fd);

	return ret;

}