Mapping Hardware

#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <linux/fb.h>
#include <unistd.h>
#include <stropts.h>
 
int main(void)
{
    int i,memfd;
    unsigned long *memregs32;
 
    memfd = open("/dev/mem", O_RDWR);
 
    memregs32 = mmap(0, 0x1000, PROT_READ|PROT_WRITE,
            MAP_SHARED, memfd, 0x101e8000);
 
    printf ("RTC value = %04X\n", memregs32[0]);
    sleep(2);
    printf ("RTC value = %04X\n", memregs32[0]);
    memregs32[2] = 0x1000;
    sleep(2);
    printf ("RTC value = %04X\n", memregs32[0]);
 
    close (memfd);
    printf("test complete\n");
    return 0;
}