accessing Sun physical memory

[John C Schultz]

mcvax!aivru.sheffield.ac.uk!chris at uunet.uu.net (Chris Brown) writes:
>Mike Martys in v7n192:
>
>> Another way is to manipulate the page map, mapping some part of the
>> ......
>
>This is precisely what mmap(2) does. Read the manual page. Also there is
>....

I also use mmap() to map image framebuffers and board control without
having to write device drivers for what are pretty simple (in one sense)
image processing boards.  The problem that I ran into is that for buffers
> 128KB, the SUN mapper only marks the page invalid on a munmap().  That
space NEVER AGAIN can be used for that process.  However, it turns out
that if you don't read the manual carefully enough :-), you can mmap() the
same space again and it will work most of the time but occasionally crash
on a segment violation.

My solution is to mmap()/munmap() small things like board control
registers while only mmap()ing large things like framebuffers once and
just remembering that you have mmap()ed the buffers so subsequent calls do
nothing.  Works fine. -- 

 john c. schultz   schultz at 3M.Com   ..!uiucuxc!mmm!schultz  (612) 733-4047
           3M Center, Bldg 518-1-1, St. Paul, MN 55144-1000
  The opinions expressed herein are, as always, my own and not 3M's.