OUTB(2) Linux Programmer's Manual OUTB(2)
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 optimiza-
tion 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)
Linux 2017-09-15 OUTB(2)
