man-pages/man2/outb.2.html
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<H1>OUTB</H1>
Section: Linux Programmer's Manual (2)<BR>Updated: 2017-09-15<BR><A HREF="#index">Index</A>
<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
<A NAME="lbAB">&nbsp;</A>
<H2>NAME</H2>
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
<A NAME="lbAC">&nbsp;</A>
<H2>SYNOPSIS</H2>
<PRE>
<B>#include &lt;<A HREF="file:///usr/include/sys/io.h">sys/io.h</A>&gt;</B>
<B>unsigned char inb(unsigned short int </B><I>port</I><B>);</B>
<B>unsigned char inb_p(unsigned short int </B><I>port</I><B>);</B>
<B>unsigned short int inw(unsigned short int </B><I>port</I><B>);</B>
<B>unsigned short int inw_p(unsigned short int </B><I>port</I><B>);</B>
<B>unsigned int inl(unsigned short int </B><I>port</I><B>);</B>
<B>unsigned int inl_p(unsigned short int </B><I>port</I><B>);</B>
<B>void outb(unsigned char </B><I>value</I><B>, unsigned short int </B><I>port</I><B>);</B>
<B>void outb_p(unsigned char </B><I>value</I><B>, unsigned short int </B><I>port</I><B>);</B>
<B>void outw(unsigned short int </B><I>value</I><B>, unsigned short int </B><I>port</I><B>);</B>
<B>void outw_p(unsigned short int </B><I>value</I><B>, unsigned short int </B><I>port</I><B>);</B>
<B>void outl(unsigned int </B><I>value</I><B>, unsigned short int </B><I>port</I><B>);</B>
<B>void outl_p(unsigned int </B><I>value</I><B>, unsigned short int </B><I>port</I><B>);</B>
<B>void insb(unsigned short int </B><I>port</I><B>, void *</B><I>addr</I><B>,</B>
<B> unsigned long int </B><I>count</I><B>);</B>
<B>void insw(unsigned short int </B><I>port</I><B>, void *</B><I>addr</I><B>,</B>
<B> unsigned long int </B><I>count</I><B>);</B>
<B>void insl(unsigned short int </B><I>port</I><B>, void *</B><I>addr</I><B>,</B>
<B> unsigned long int </B><I>count</I><B>);</B>
<B>void outsb(unsigned short int </B><I>port</I><B>, const void *</B><I>addr</I><B>,</B>
<B> unsigned long int </B><I>count</I><B>);</B>
<B>void outsw(unsigned short int </B><I>port</I><B>, const void *</B><I>addr</I><B>,</B>
<B> unsigned long int </B><I>count</I><B>);</B>
<B>void outsl(unsigned short int </B><I>port</I><B>, const void *</B><I>addr</I><B>,</B>
<B> unsigned long int </B><I>count</I><B>);</B>
</PRE>
<A NAME="lbAD">&nbsp;</A>
<H2>DESCRIPTION</H2>
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.
<P>
They are primarily designed for internal kernel use,
but can be used from user space.
<P>
You must compile with <B>-O</B> or <B>-O2</B> or similar.
The functions
are defined as inline macros, and will not be substituted in without
optimization enabled, causing unresolved references at link time.
<P>
You use
<B><A HREF="/cgi-bin/man/man2html?2+ioperm">ioperm</A></B>(2)
or alternatively
<B><A HREF="/cgi-bin/man/man2html?2+iopl">iopl</A></B>(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.
<A NAME="lbAE">&nbsp;</A>
<H2>CONFORMING TO</H2>
<B>outb</B>()
and friends are hardware-specific.
The
<I>value</I>
argument is passed first and the
<I>port</I>
argument is passed second,
which is the opposite order from most DOS implementations.
<A NAME="lbAF">&nbsp;</A>
<H2>SEE ALSO</H2>
<B><A HREF="/cgi-bin/man/man2html?2+ioperm">ioperm</A></B>(2),
<B><A HREF="/cgi-bin/man/man2html?2+iopl">iopl</A></B>(2)
<A NAME="lbAG">&nbsp;</A>
<H2>COLOPHON</H2>
This page is part of release 5.05 of the Linux
<I>man-pages</I>
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
<A HREF="https://www.kernel.org/doc/man-pages/.">https://www.kernel.org/doc/man-pages/.</A>
<P>
<HR>
<A NAME="index">&nbsp;</A><H2>Index</H2>
<DL>
<DT id="1"><A HREF="#lbAB">NAME</A><DD>
<DT id="2"><A HREF="#lbAC">SYNOPSIS</A><DD>
<DT id="3"><A HREF="#lbAD">DESCRIPTION</A><DD>
<DT id="4"><A HREF="#lbAE">CONFORMING TO</A><DD>
<DT id="5"><A HREF="#lbAF">SEE ALSO</A><DD>
<DT id="6"><A HREF="#lbAG">COLOPHON</A><DD>
</DL>
<HR>
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