#include <unistd.h>
#include <stdint.h>
#include <fcntl.h>
#include <sys/random.h>

#define LED_FILE	"/sys/devices/platform/thinkpad_acpi/leds/tpacpi::lid_logo_dot/brightness"

int main(void) {
    int fd_led;
    uint32_t r[1];
    
    fd_led = open(LED_FILE, O_WRONLY);
    if (fd_led == -1) {
        write(2,"Can't open led control file.\n",29);
        return -1;
    }
    while(1) {
        usleep(50000);
        write(fd_led,"0",2);
        getrandom(r, sizeof(*r), GRND_NONBLOCK);
        usleep(*r&0x001fffff);
        write(fd_led,"255",4);
    }
    return 0;
}