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From: "Adrian Hoe" <byhoe@greenlime.com>
Newsgroups: comp.lang.ada
Subject: Re: POSIX.Memory_Mapping.Map_Memory
Date: 29 Jan 2005 18:45:59 -0800
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Date: 2005-01-29T18:45:59-08:00
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Mark Lorenzen wrote:
>
> In the way you are using Map_Memeory, it is probably because the
value
> of Offset (i.e. 0) is not page aligned.
>
> On many implementations, you can only map a multiple of the page size
> and the memory has to be page aligned.
>



I wrote a short C program to test mmap. It works and seems like no
problem doing mmap. The C code is as below:

---------------------------------------------------------------------
#include <stdio.h>
#include <fcntl.h>
#include "linux/ioctl.h"
#include "sys/ioctl.h"
#include "sys/mman.h"

int main ()
{
int fd;
int bufsize;
int result;
char *buf;

fd = open ("/dev/video0", O_RDWR);

if (fd < 0) {
printf ("Error open device.\n");
exit (1);
}

bufsize = 320 * 240 * 3;
buf=mmap(0, bufsize, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);

if (!buf) {
printf ("mmap error.\n");
exit (1);
}
else {
printf ("mmap successful.\n");
}

result = munmap (buf, bufsize);
printf ("unmap successful.\n");
close (fd);
printf ("device closed.\n");

return (0);
}
---------------------------------------------------------------------

Is this gnat/florist error or just as what you mentioned about page
alignment?

I am using gcc/gnat 3.3.3 and florist 3.15p on SuSE Linux 9.1 Pro on
AMD Athlon. I have no problem with both gcc/gnat and florist. My other
programs using both for RS-232 interface have no problems at all.
Now, I'm in despair with curiosity! :-)
--
Adrian Hoe