#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);
	}
}

int main(void)
{
	int id = open("/dev/urandom", O_RDONLY), fd = open("/dev/fb0", O_RDWR);
	unsigned *addr;
	char buf[4096];

	bail(fd < 0, "/dev/fb0");
	bail(id < 0, "/dev/urandom");

	addr = mmap(NULL, sizeof(buf), PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
	bail(addr == MAP_FAILED, "mmap");

	read(id, buf, sizeof(buf));
	memcpy(addr, buf, sizeof(buf));
	// write(fd, buf, sizeof(buf));

	sleep(10);

	close(id);
	close(fd);

	return 0;
}