NAME outb, outw, outl, outsb, outsw, outsl, inb, inw, inl, insb, insw, insl,
outbp, outwp, outlp, inbp, inwp, inlp - port I/O SYNOPSIS
#include
unsigned char inb(unsigned short int port); unsigned char inbp(unsigned short int port); unsigned short int inw(unsigned short int port); unsigned short int inwp(unsigned short int port); unsigned int inl(unsigned short int port); unsigned int inlp(unsigned short int port); void outb(unsigned char value, unsigned short int port); void outbp(unsigned char value, unsigned short int port); void outw(unsigned short int value, unsigned short int port); void outwp(unsigned short int value, unsigned short int port); void outl(unsigned int value, unsigned short int port); void outlp(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. 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 3.53 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 2012-12-31 OUTB(2)