Provided by: manpages-dev_3.35-0.1ubuntu1_all bug


       outb,  outw,  outl,  outsb, outsw, outsl, inb, inw, inl, insb, insw, insl, outb_p, outw_p,
       outl_p, inb_p, inw_p, inl_p - port I/O


       This family of functions is used  to  do  low-level  port  input  and  output.   The  out*
       functions  do  port  output,  the  in* functions do port input; the b-suffix functions are
       byte-width and the w-suffix functions word-width; the _p-suffix functions pause until  the
       I/O completes.

       They are primarily designed for internal kernel use, but can be used from user space.

       You  compile  with  -O or -O2 or similar.  The functions are defined as inline macros, and
       will not be substituted in without optimization enabled, causing unresolved references  at
       link time.

       You  use  ioperm(2)  or  alternatively  iopl(2) to tell the kernel to allow the user space
       application to access the I/O ports in question.   Failure  to  do  this  will  cause  the
       application to receive a segmentation fault.


       outb() and friends are hardware-specific.  The value argument is passed first and the port
       argument is passed second, which is the opposite order from most DOS implementations.


       ioperm(2), iopl(2)


       This page is part of release 3.35 of the Linux man-pages project.  A  description  of  the
       project,  and information about reporting bugs, can be found at