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

       ioperm - set port input/output permissions

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

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

       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 dis‐
       abled.  If turn_on is nonzero, the calling thread  must	be  privileged

       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);  follow‐
       ing  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 architec‐
       tures it does not exist or will always return an error.

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

       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.

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

       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.

       iopl(2), outb(2), capabilities(7)

       This page is part of release 3.65 of the Linux  man-pages  project.   A
       description  of	the project, and information about reporting bugs, can
       be found at

Linux				  2013-03-12			     IOPERM(2)

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