OUTB Section: Linux Programmer's Manual (2) Updated: November 29, 2025 Index   NAME outb, outw, outl, outsb, outsw, outsl - port output inb, inw, inl, insb, insw, insl - port input outb_p, outw_p, outl_p, inb_p, inw_p, inl_p - paused I/O   DESCRIPTION This family of functions is used to do low level port input and output. They are primarily designed for internal kernel use, but can be used from user space, given the following information in addition to that given in You 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 or alternatively 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 port and value arguments are in the opposite order to most DOS implementations.   SEE ALSO   Index NAME DESCRIPTION CONFORMING TO SEE ALSO This document was created by using the manual pages. Time: 11:56:06 GMT, March 24, 2025