[avr-gcc-list] C structs for Hardware definitions

[Larry Barello]

Before I go type in a bunch of stuff, is there any good reason why C structs & 
bitfields
can't be used to access hardware, like the USART control registers?  Is it a 
matter of
efficiency: with a dereferenced pointer GCC has to treat it like memory and not 
use the
bit test/set instructions?  Or is it dealing with the screwy I/O map of the 
AVR?  Then I
can write one set of handlers for the USARTs and pass the pointer to make 
things happen.

e.g.

typedef struct
{
    unsigned char UDR;
    struct
    {
        unsigned char bitthis:1;
        unsigned char bitthat:1;
        unsigned char etc:3;
    } USCRA;
    struct
    {
        ...
    } USCRB;
    ...
    unsigned UBRR;

} *pUSART;

pUSART USART0 = 0xXX, USART1 = 0xYYY;

...

if (USART0->bitthis == 0) ...

----
Larry Barello
www.barello.net