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       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 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.

       This  call  is  mostly  for  the  i386  architecture.   On  many  other
       architectures 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 ppc) This call is not supported.

       EPERM  The calling process has insufficient privilege to call ioperm();
              the CAP_SYS_RAWIO capability is required.


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


       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), capabilities(7)