#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <signal.h>
#include <errno.h>
#include <string.h>

void sigint(int sig)
{
	fprintf(stderr, "Keyboard Interrupt\n");
	return;
}

int pm_qos_fd = -1;

int start_low_latency(void)
{
	int32_t target = 0;
	int ret;

	if (pm_qos_fd >= 0)
		return 0;
	if ((pm_qos_fd = open("/dev/cpu_dma_latency", O_WRONLY)) == -1) {
		fprintf(stderr, "Failed to open /dev/cpu_dma_latency: %s\n", strerror(errno));
		return errno;
	}

	if ((ret = write(pm_qos_fd, &target, sizeof(target))) <= 0) {
		fprintf(stderr, "Failed to write zero to /dev/cpu_dma_latency: %s\n", strerror(errno));
		return errno;
	}
	return 0;
}

void stop_low_latency(void)
{
	if (pm_qos_fd >= 0)
		close(pm_qos_fd);
}

int main(int argc, char **argv)
{
	int ret;


	if (start_low_latency()) {
		fprintf(stderr, "failed to enter low-latency mode!\n");
		exit(-1);
	}
	signal(SIGINT, sigint);
	printf("pausing with /dev/cpu_dma_latency open\n");
	pause();
	printf("closing /dev/cpu_dma_latency\n");
	stop_low_latency();
	exit(0);
}