#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <signal.h>
#include <fcntl.h>
#include <sys/mman.h>

#define ERROR() do { fprintf(stderr, "Error at line %d, file %s (%d) [%s]\n", \
  __LINE__, __FILE__, errno, strerror(errno)); exit(1); } while(0)

#define MAP_SIZE 4096UL
#define MAP_MASK (~-MAP_SIZE)

void sigint(int signo){
	(void)signo;
}

int main(int argc, char **argv){
	int fd;
	volatile unsigned long *map_base;
	off_t target;
	off_t mmconfig_base;
	int bus;
	int dev;
	int i;

	signal(SIGINT, sigint);

	mmconfig_base = 0xe0000000;
	bus = 4; dev = 9;
	target = mmconfig_base + 0x100000 * bus + 0x8000 * dev;

	if ((fd = open("/dev/mem", O_RDWR | O_SYNC)) == -1) ERROR();
	printf("/dev/mem opened.\n");
	fflush(stdout);

	map_base = (unsigned long *)mmap(0, MAP_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, target & ~MAP_MASK);
	if (map_base == (void *) -1) ERROR();
	printf("Memory mapped at address %p.\n", map_base);
	fflush(stdout);

	for(i=0;i<256;i++){
		map_base[0] = i << 2;
		map_base[1] = i;
		map_base[2] = i >> 2;
		map_base[3] = i >> 4;
		usleep(100 * 1000);
		if(EINTR == errno){
			printf("BREAK\n");
			break;
		}
	}

	if(munmap((void *)map_base, MAP_SIZE) == -1) ERROR();
	close(fd);
	return 0;
}