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
LIBRARY
Standard C library (libc, -lc)
SYNOPSIS
#include <sys/io.h>unsigned char inb(unsigned short \nport\n);\n
\nunsigned char inb_p(unsigned short \nport\n);\n
\nunsigned short inw(unsigned short \nport\n);\n
\nunsigned short inw_p(unsigned short \nport\n);\n
\nunsigned int inl(unsigned short \nport\n);\n
\nunsigned int inl_p(unsigned short \nport\n);void outb(unsigned char \nvalue\n, unsigned short \nport\n);\n
\nvoid outb_p(unsigned char \nvalue\n, unsigned short \nport\n);\n
\nvoid outw(unsigned short \nvalue\n, unsigned short \nport\n);\n
\nvoid outw_p(unsigned short \nvalue\n, unsigned short \nport\n);\n
\nvoid outl(unsigned int \nvalue\n, unsigned short \nport\n);\n
\nvoid outl_p(unsigned int \nvalue\n, unsigned short \nport\n);void insb(unsigned short \nport\n, void \naddr\n[.\ncount\n],\n
\n unsigned long \ncount\n);\n
\nvoid insw(unsigned short \nport\n, void \naddr\n[.\ncount\n],\n
\n unsigned long \ncount\n);\n
\nvoid insl(unsigned short \nport\n, void \naddr\n[.\ncount\n],\n
\n unsigned long \ncount\n);\n
\nvoid outsb(unsigned short \nport\n, const void \naddr\n[.\ncount\n],\n
\n unsigned long \ncount\n);\n
\nvoid outsw(unsigned short \nport\n, const void \naddr\n[.\ncount\n],\n
\n unsigned long \ncount\n);\n
\nvoid outsl(unsigned short \nport\n, const void \naddr\n[.\ncount\n],\n
\n unsigned long \ncount\n);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. Failure to do this will cause the application to receive a segmentation fault.
VERSIONS
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.
STANDARDS
None.
SEE ALSO
ioperm(2), iopl(2)