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.
On success, zero is returned. On error, -1 is returned, and errno is
ioperm is Linux specific and should not be used in programs intended to
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
Linux 1993-01-21 IOPERM(2)
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