>From riku.saikkonen@compart.fi Tue Oct 18 13:01:34 EDT 1994

A number of people have been asking for this...

To use IO ports in C programs:
1. #include <asm/io.h>
2. Call ioperm(port,num,1) at somewhere near the start of the program
(before accessing ports).
3. Access ports using value=inb(port) and outb(value,port) (note the
order of the parameters). Look into asm/io.h for more system calls.
4. Call ioperm(port,num,0) at somewhere near the end of the program
(after all port accesses).
5. Compile your code with -O2 or a higher number, and no -g. (Sorry, you
can't debug...)
6. The executable has to be setuid root.

ioperm() syntax (also see the man page):
The first parameter is the port number to set permissions of.
The second parameter is the number of consecutive ports to set
permissions of (i.e. if num==3, port, port+1, and port+2 are set).
The third parameter is 1 to give the program permissions or 0 to remove
them.

Not too difficult... By the way, if anyone wants to add this to a FAQ or
HOW-TO, feel free (but contact me first).

-=- Rjs -=- riku.saikkonen@compart.fi - IRC: Rjs
"From cavern pale the moist moon eyes / the white mists that from earth
arise / to hide the morrow's sun and drip / all the grey day from each
twig's tip." - J. R. R. Tolkien