low.c

#include <stdio.h>
#include <fcntl.h>
#include <stdint.h>

int main(int argc, char **argv) {
 int32_t l;
 int fd;

 if (argc != 2) {
 fprintf(stderr, "Usage: %s <latency in us>\n", argv[0]);
 return 2;
 }

 l = atoi(argv[1]);
 printf("setting latency to %d us\n", l);
 fd = open("/dev/cpu_dma_latency", O_WRONLY);
 if (fd < 0) {
 perror("open /dev/cpu_dma_latency");
 return 1;
 }
 if (write(fd, &l, sizeof(l)) != sizeof(l)) {
 perror("write to /dev/cpu_dma_latency");
 return 1;
 }
 while (1) pause();
}