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


     This family of functions is used to do low level port  input
     and output.  They are primarily designed for internal kernel
     use, but can be used from user space,  given  the  following
     information in addition to that given in outb(9)

     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  ker-
     nel  to  allow  the user space application to access the I/O
     ports in question. Failure to do this will cause the  appli-
     cation to receive a segmentation fault.


     outb and friends are hardware specific. The port  and  value
     arguments  are in the opposite order to most DOS implementa-


     outb(9), ioperm(2), iopl(2)