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.