redhat man page for ioperm

IOPERM(2)						     Linux Programmer's Manual							 IOPERM(2)

NAME
       ioperm - set port input/output permissions

SYNOPSIS
       #include <unistd.h> /* for libc5 */
       #include <sys/io.h> /* for glibc */

       int ioperm(unsigned long from, unsigned long num, int turn_on);

DESCRIPTION
       Ioperm sets the port access permission bits for the process for num bytes starting from port address from to the value turn_on.	The use of
       ioperm requires root privileges.

       Only the first 0x3ff I/O ports can be specified in this manner.	For more ports, the iopl function  must  be  used.   Permissions  are  not
       inherited on fork, but on exec they are. This is useful for giving port access permissions to non-privileged tasks.

RETURN VALUE
       On success, zero is returned.  On error, -1 is returned, and errno is set appropriately.

CONFORMING TO
       ioperm is Linux specific and should not be used in programs intended to be portable.

NOTES
       Libc5  treats  it  as  a  system  call and has a prototype in <unistd.h>.  Glibc1 does not have a prototype. Glibc2 has a prototype both in
       <sys/io.h> and in <sys/perm.h>.	Avoid the latter, it is available on i386 only.

SEE ALSO
       iopl(2)

Linux								    1993-01-21								 IOPERM(2)