test_cpu_qos.c

#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <signal.h>

#define QOS_DEV "/dev/cpu_wakeup_latency"
#define LATENCY_VAL "0x7a110"  /* <500000 ?unit? in hex */

static volatile int keep_running = 1;

void sig_handler(int sig) {
    keep_running = 0;
}

int main(void) {
    int fd;

    signal(SIGINT, sig_handler);
    signal(SIGTERM, sig_handler);

    fd = open(QOS_DEV, O_RDWR);
    if (fd < 0) {
        perror("open");
        return 1;
    }

    if (write(fd, LATENCY_VAL, sizeof(LATENCY_VAL) - 1) < 0) {
        perror("write");
        close(fd);
        return 1;
    }

    printf("QoS set to %s. Press Ctrl+C to exit.\n", LATENCY_VAL);

    while (keep_running)
        sleep(1);

    close(fd);
    printf("Released.\n");
    return 0;
}