ioperm(2)

1IOPERM(2)                  Linux Programmer's Manual                 IOPERM(2)
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NAME

6       ioperm - set port input/output permissions
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SYNOPSIS

9       #include <unistd.h> /* for libc5 */
10       #include <sys/io.h> /* for glibc */
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12       int ioperm(unsigned long from, unsigned long num, int turn_on);
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DESCRIPTION

15       ioperm()  sets  the port access permission bits for the calling process
16       for num bytes starting from port address from to the value turn_on.  If
17       turn_on   is   nonzero,   the   calling   process  must  be  privileged
18       (CAP_SYS_RAWIO).
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20       Only the first 0x3ff I/O ports can be specified in  this  manner.   For
21       more ports, the iopl(2) system call must be used.
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23       Permissions are not inherited by the child created by fork(2).  Permis‐
24       sions are preserved across execve(2); this is useful  for  giving  port
25       access permissions to unprivileged programs.
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27       This call is mostly for the i386 architecture.  On many other architec‐
28       tures it does not exist or will always return an error.
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RETURN VALUE

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

35       EINVAL Invalid values for from or num.
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37       EIO    (on PowerPC) This call is not supported.
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39       ENOMEM Out of memory.
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41       EPERM  The calling process has insufficient privilege.
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CONFORMING TO

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

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

57       This  page  is  part of release 3.25 of the Linux man-pages project.  A
58       description of the project, and information about reporting  bugs,  can
59       be found at http://www.kernel.org/doc/man-pages/.
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63Linux                             2007-06-15                         IOPERM(2)