Is fdisk divides address space for created partition? - linux

Question

On my system, it has one mem node created already in /dev (/dev/pmem). then i use fdisk command for creating a partition
After creating partition I apply lsblk command and my result is
pmem1 259:4 0 15.8G 0 disk
└─pmem1p2 259:7 0 14.3G 0 part
After that, I write mmap code (Refer devmam library) just like
off_t address = 0x00;
int width = 10;
void *virtladdr, *phyaddr;
int a = 5;
int *lendata = &a;
int main(void)
{
int mode = 0x0777;
char *filename = "/dev/pmem0";
int fdout;
if ((fdout = open (filename, O_RDWR | O_CREAT | O_TRUNC, mode )) < 0)//edited here
{
printf ("can't create file");
return 0;
}
mapped_size = page_size = getpagesize();
offset_in_page = (uint64_t)address & (page_size - 1);
if (offset_in_page + (width * 8) > page_size) {
mapped_size *= 2;
}
printf("map size %ld\n", mapped_size);
phyaddr = mmap(0, mapped_size, (PROT_READ | PROT_WRITE), MAP_SHARED, fdout, address & ~(off_t)(page_size - 1));
1 = I write value 10 on 0x00 address for /dev/pmem1
2 = I write value 20 on 0x00 address for /dev/pmem1p2
Then after I Read mmap
off_t address = 0x00;
int width = 10;
int main(void)
{
int retVal = -1;
int fd;
unsigned long mapped_size, page_size, offset_in_page;
void *virtladdr, *phyaddr;
fd = open("/dev/pmem0", O_RDWR | O_SYNC);
if(fd < 0)
{
printf("file not open \n");
}
mapped_size = page_size = getpagesize();
offset_in_page = (uint64_t)address & (page_size - 1);
if (offset_in_page + (width * 8) > page_size) {
mapped_size *= 2;
}
/* Map one page */
phyaddr = mmap(0, mapped_size, PROT_READ,MAP_PRIVATE , fd, address & ~(off_t)(page_size - 1));
1 = Read 0x00 address from /dev/pmem1 My output is 10
2 = Read 0x00 address from /dev/pmem1p2 My output is 20
So what happened here why 0th address value is different? Is fdisk create two partitions which address starts from 0x00? Or I am in the wrong way?