NAME

       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

SYNOPSIS

       #include <sys/io.h>

       unsigned char inb(unsigned short int port);
       unsigned char inb_p(unsigned short int port);
       unsigned short int inw(unsigned short int port);
       unsigned short int inw_p(unsigned short int port);
       unsigned int inl(unsigned short int port);
       unsigned int inl_p(unsigned short int port);

       void outb(unsigned char value, unsigned short int port);
       void outb_p(unsigned char value, unsigned short int port);
       void outw(unsigned short int value, unsigned short int port);
       void outw_p(unsigned short int value, unsigned short int port);
       void outl(unsigned int value, unsigned short int port);
       void outl_p(unsigned int value, unsigned short int port);

       void insb(unsigned short int port, void *addr,
                  unsigned long int count);
       void insw(unsigned short int port, void *addr,
                  unsigned long int count);
       void insl(unsigned short int port, void *addr,
                  unsigned long int count);
       void outsb(unsigned short int port, const void *addr,
                  unsigned long int count);
       void outsw(unsigned short int port, const void *addr,
                  unsigned long int count);
       void outsl(unsigned short int port, const void *addr,
                  unsigned long int count);

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  must 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.

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  5.05  of  the  Linux man-pages project.  A description of the project,
       information  about  reporting  bugs,  and  the  latest  version  of  this   page,   can   be   found   at
       https://www.kernel.org/doc/man-pages/.

Linux                                              2017-09-15                                            OUTB(2)