Hi Dan, thanks for your quick response! I was using a reference to mmap from
this page:
http://www.opengroup.org/onlinepubs/000095399/functions/mmap.html
which states that mmap will return MAP_FAILED if there is an error and the
error will be located in errno. please correct me if this is wrong. As such
i don't believe that the map is failing.
i did in any case make the size modulo with PAGE_SIZE (=4096) as found in
asm-ppc/page.h which unfortunately did not fix the problem. just for the heck
of it I also tried every size from 1 up to 65536...
It's worth noting that I also tried treating /dev/mem as a file (as it was
intended) by using functions lseek, read, and write. read and write returned a
value of zero upon completion, indicating that no bytes were read/written. I
get the feeling that file I/O functions failing on /dev/mem indicates something
important, but I'm not sure what. especially since /dev/mem operations DO work
on other parts of physical memory (such as RAM).
--scott
----- Original Message ----
From: Dan Malek <[EMAIL PROTECTED]>
To: scott <scotto2hot-green at yahoo.com>
Cc: linuxppc-embedded at ozlabs.org
Sent: Friday, July 28, 2006 11:51:03 AM
Subject: Re: using /dev/mem to talk to peripherals on VIIP system
On Jul 28, 2006, at 1:35 PM, scott wrote:
> ptr = MAP_FAILED; // Initialize to bad value
> ptr = (int *) mmap(0, 256, PROT_READ|PROT_WRITE, MAP_SHARED, fd,
> USER_LOGIC_BASEADDR);
Well, this isn't going to detect an error, since the error code
is returned instead of an address.
>
> if(ptr==MAP_FAILED) {
if ((int)ptr == -1) {
> printf("Err: cannot access address!\n");
> return -1;
> }
>
> .... Any other thoughts?
Your mmap is failing because the size is not modulo PAGE_SIZE.
-- Dan
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