#include <sys/types.h>
#include <sys/mman.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>

static void bail(int cond, const char *msg)
{
	if (cond) {
		perror(msg);
		exit(1);
	}
}

#define COUNT 100

volatile int wobble;

int main(int argc, char** argv)
{
	int fd = open("/dev/fb0", O_RDWR);
	unsigned char *addr;
	wobble = 42;

	bail(fd < 0, "/dev/fb0");
	printf("Ready to map\n");

	if (argc == 1)
		while (wobble == 42);

	addr = mmap(NULL, 4096*COUNT, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
	printf("Mapped at %p\n", addr);
	bail(addr == MAP_FAILED, "mmap");
	int i,j=0;
	
	while (wobble != 42);
	// fault the pages in if they need to be
	for(i=0; i < COUNT; i++)
		j += addr[i*4096];
	
	while (wobble == 42);
}