outb(2) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | CONFORMING TO | SEE ALSO | COLOPHON

OUTB(2)                 Linux Programmer's Manual                OUTB(2)

NAME         top

       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         top

       #include <sys/io.h>

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

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

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

DESCRIPTION         top

       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         top

       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         top

       ioperm(2), iopl(2)

COLOPHON         top

       This page is part of release 5.12 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                          2020-11-01                        OUTB(2)

Pages that refer to this page: ioperm(2)iopl(2)