centos 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 calling thread for num bits starting from port address from.  If turn_on is nonzero,
       then permission for the specified bits is enabled; otherwise it is disabled.  If turn_on is nonzero, the calling thread must be	privileged
       (CAP_SYS_RAWIO).

       Before  Linux  2.6.8,  only the first 0x3ff I/O ports could be specified in this manner.  For more ports, the iopl(2) system call had to be
       used (with a level argument of 3).  Since Linux 2.6.8, 65,536 I/O ports can be specified.

       Permissions are not inherited by the child created by fork(2); following a fork(2) the child must turn on those permissions that it  needs.
       Permissions are preserved across execve(2); this is useful for giving port access permissions to unprivileged programs.

       This call is mostly for the i386 architecture.  On many other architectures it does not exist or will always return an error.

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

ERRORS
       EINVAL Invalid values for from or num.

       EIO    (on PowerPC) This call is not supported.

       ENOMEM Out of memory.

       EPERM  The calling thread has insufficient privilege.

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

NOTES
       The /proc/ioports file shows the I/O ports that are currently allocated on the system.

       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), outb(2), capabilities(7)

COLOPHON
       This page is part of release 3.53 of the Linux man-pages project.  A description of the project, and information about reporting bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

Linux								    2013-03-12								 IOPERM(2)