netbsd man page for x86_64_iopl

X86_64_IOPL(2)						  BSD/x86_64 System Calls Manual					    X86_64_IOPL(2)

NAME
     x86_64_iopl -- change the x86_64 I/O privilege level

LIBRARY
     x86_64 Architecture Library (libx86_64, -lx86_64)

SYNOPSIS
     #include <sys/types.h>
     #include <machine/sysarch.h>

     int
     x86_64_iopl(int iopl);

DESCRIPTION
     x86_64_iopl() sets the x86_64 I/O privilege level to the value specified by iopl.	This call is restricted to the super-user.

RETURN VALUES
     Upon successful completion, x86_64_iopl() returns 0.  Otherwise, a value of -1 is returned and the global variable errno is set to indicate
     the error.

ERRORS
     x86_64_iopl() will fail if:

     [EPERM]   The caller was not the super-user, or the operation was not permitted at the current security level.

WARNING
     You can really hose your machine if you enable user-level I/O and write to hardware ports without care.

BSD
								   July 3, 2002 							       BSD