<html><head><style type="text/css"><!-- DIV {margin:0px} --></style></head><body><div style="font-family:times new roman, new york, times, serif;font-size:12pt"><div style="font-family: times new roman,new york,times,serif; font-size: 12pt;">Hi Dan, thanks for your quick response! I was using a reference to mmap from this page:<br><span><a target="_blank" href="http://www.opengroup.org/onlinepubs/000095399/functions/mmap.html">http://www.opengroup.org/onlinepubs/000095399/functions/mmap.html</a></span><br>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.<br><br>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...<br><br>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).<br><br>--scott<br><br><div style="font-family: times new roman,new york,times,serif; font-size: 12pt;">----- Original Message ----<br>From: Dan Malek <dan@embeddedalley.com><br>To: scott <scotto2hot-green@yahoo.com><br>Cc: linuxppc-embedded@ozlabs.org<br>Sent: Friday, July 28, 2006 11:51:03 AM<br>Subject: Re: using /dev/mem to talk to peripherals on VIIP system<br><br><div><br>On Jul 28, 2006, at 1:35 PM, scott wrote:<br><br>> ptr = MAP_FAILED; // Initialize to bad value<br>> ptr = (int *) mmap(0, 256, PROT_READ|PROT_WRITE,
MAP_SHARED, fd, <br>> USER_LOGIC_BASEADDR);<br><br>Well, this isn't going to detect an error, since the error code<br>is returned instead of an address.<br><br>><br>> if(ptr==MAP_FAILED) {<br><br> if ((int)ptr == -1) {<br>> printf("Err: cannot access address!\n");<br>> return -1;<br>> }<br>><br><br>> .... Any other thoughts?<br><br>Your mmap is failing because the size is not modulo PAGE_SIZE.<br><br><br> -- Dan<br><br></div></div><br></div></div></body></html>