outb

       outb_p, outw_p, outl_p, inb_p, inw_p, inl_p - port I/O

DESCRIPTION
       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.  Fail-
       ure to do this will cause the application  to  receive  a  segmentation
       fault.

CONFORMING TO
       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.

SEE ALSO
       ioperm(2), iopl(2)

COLOPHON
       This  page  is  part of release 3.23 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.



Linux                             1995-11-29                           OUTB(2)
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