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

int main()
{
        volatile u_int32_t *gpio;
        int dev_mem_fd;
        u_int32_t x;
        int i;

        dev_mem_fd = open("/dev/mem", O_RDWR | O_SYNC);
        if (dev_mem_fd < 0) {
                perror("open(\"/dev/mem\")");
                exit(-1);
        }

        gpio = mmap(0, 4096, PROT_READ | PROT_WRITE, MAP_SHARED, dev_mem_fd, 0xc8004000);
        if (gpio == MAP_FAILED) {
                perror("mmap");
                exit(-1);
        }

        x = gpio[0];
        printf("value is %.8x\n", x);
        for (i=0;i<1024*1048576;i++)
                // gpio[0] = x;
                x = gpio[2];

        munmap((void *)gpio, 4096);

        return 0;
}