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Re: GPIO on the Au1500

To: <>
Subject: Re: GPIO on the Au1500
From: "Gilad Rom" <>
Date: Sun, 14 Nov 2004 17:53:49 +0200
Organization: Romat Telecom
Original-recipient: rfc822;
References: <> <09ac01c4ca24$e68a6740$a701a8c0@lan>
Replying to myself -
I've composed a small program which mmap()'s
SYS_BASE and then tries to read at the appropriate
GPIO offset, as defined in the Au1500 databook.

For some reason, I keep getting that magical value, 0x10000001 for EVERY address I try to read, be it SYS_BASE (0xB1900000) or every other address. (for example,
I've tried reading the MAC address from the MAC0 base address
of 0xB1500000, offset 0x0008, and I always get 0x10000001).

Any reason I shouldn't succeed in reading the au1500 hardware addresses through /dev/mem?

Attached is the code I'm using:

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/mman.h>

#define SYS_BASE     0xB1900000

main () {
volatile unsigned long *base;
unsigned char val;
int f, i;

f = open ("/dev/mem", O_RDWR | O_SYNC);
if (f < 0) {
 perror ("fopen");
 exit (-1);

base = (unsigned long *) mmap (NULL, getpagesize (), PROT_READ | PROT_WRITE, MAP_SHARED, f,

if (base == (unsigned long *) (-1)) {
 perror ("mmap");
 exit (-1);

printf ("data at %p: 0x%x\n", base, (unsigned long) *base);
*base = 0xffffffff;
       printf ("data at %p: 0x%x\n", base, (unsigned long) *base);
close (f);
return (0);


----- Original Message ----- From: "Gilad Rom" <>
To: <>; <>
Sent: Sunday, November 14, 2004 10:35 AM
Subject: Re: GPIO on the Au1500

Thanks. Can't I just mmap /dev/mem and use the
GPIO offset from SYS_BASE?


----- Original Message ----- From: "Pete Popov" <>
To: "Gilad Rom" <>; <>
Sent: Friday, November 12, 2004 8:13 PM
Subject: Re: GPIO on the Au1500

--- Gilad Rom <> wrote:


I am trying to use the au1000_gpio driver, but I'm a
little clueless as to how it is meant to be used. Can I use the GPIO ioctl's from a userland program, or must I write a kernel module?

I'll see if I can dig up some docs and the example
userland program this weekend. That driver hasn't been
tested in a while though.


Thank you,
Gilad Rom
Romat Telecom

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