[avr-libc-dev] Bug #28901 - GPIO_t and CPU_t definitions

[Boyapati, Anitha]

Hi,

This is w.r.t Bug #28901. It says GPIO and CPU are defined in terms of missing 
definitions in all XMEGA headers.

One such example is:
#define GPIO    (*(GPIO_t *) 0x0000)  /* General Purpose IO Registers */
#define CPU    (*(CPU_t *) 0x0030)  /* CPU Registers */


I am trying to understand GPIO and CPU from a programmer perspective.

1. What purpose do GPIO and CPU definitions serve? 
2. If possible pl provide more info on how the structures are intended to be 
defined/used


Regards
Anitha