#include <stdio.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <linux/fb.h>
#include <errno.h>
#include <unistd.h>
#define aa errno
#define OFF_GPIOH          (0x0837)
#define PWR_TFT_BIT        (2)
char buf[100];

void *trymmap (void *start, size_t length, int prot, int flags, int fd, off_t offset)
{
   char *p;
   int aa;

   sprintf (buf,"mmap(%X, %X, %X, %X, %X, %X) ... ", (unsigned int)start, length, prot, flags, fd, (unsigned int)offset);
   printf (buf);
   p = mmap (start, length, prot, flags, fd, offset);
   if (p == (char *)0xFFFFFFFF)
      sprintf (buf,"failed. errno = %d\n", aa);
   else
      sprintf (buf,"OK! (%X)\n", (unsigned int)p);

   return (void *)p;
}


int main(int argc, char **argv)
{
   int i;
   int memfd;
   unsigned short tfton, tftoff;
   unsigned short *mmCpuRegisters;

   /* Small initial delay, to let everything settle */
   for (i=0;i<100000;i++);

   memfd = open("/dev/mem", O_RDWR);
   if (memfd == -1)
   {
      printf ("/dev/mem open failed\n");
      return 0;
   }

   sprintf (buf,"/dev/mem opened successfully - fd = %d\n", memfd);
   printf (buf);

   mmCpuRegisters = (unsigned short *)trymmap(0, 0x10000, PROT_READ | PROT_WRITE, MAP_SHARED, memfd, 0xc0000000);
   if (mmCpuRegisters == (unsigned short *)0xFFFFFFFF)
   {
      printf ("Failed to map CPU registers\n");
      return 1;
   }

   tfton = mmCpuRegisters[OFF_GPIOH] | (1<<PWR_TFT_BIT);
   tftoff = tfton & (~(1<<PWR_TFT_BIT));


//         mmCpuRegisters[OFF_GPIOH] = tfton;
         mmCpuRegisters[OFF_GPIOH] = tftoff;


return 0;
}