.TH INB 10 x86
.SH NAME
inb, ins, inl, outb, outs, outl, insb, inss, insl, outsb, outss, outsl \- programmed I/O
.SH SYNOPSIS
.ta \w'\fLushort 'u
.B
int	inb(int port)
.PP
.B
ushort	ins(int port)
.PP
.B
ulong	inl(int port)
.PP
.B
void	outb(int port, int value)
.PP
.B
void	outs(int port, ushort value)
.PP
.B
void	outl(int port, ulong value)
.PP
.B
void	insb(int port, void *address, int count)
.PP
.B
void	inss(int port, void *address, int count)
.PP
.B
void	insl(int port, void *address, int count)
.PP
.B
void	outsb(int port, void *address, int count)
.PP
.B
void	outss(int port, void *address, int count)
.PP
.B
void	outsl(int port, void *address, int count)
.SH DESCRIPTION
The
.I x86
implementation provides functions to allow kernel code
written in C to access the I/O address space.
On several other architectures such as the PowerPC and Strongarm,
the platform-dependent code provides similar functions to access
devices with an I/O space interface, even when that is memory mapped, to encourage portability of device drivers.
.PP
.IR Inb ,
.I ins
and
.I inl
apply the corresponding hardware instruction to fetch the next byte, short or long
from the I/O
.IR port .
.IR Outb ,
.I outs
and
.I outl
output a
.I value
to the I/O
.IR port .
.PP
The remaining functions transfer
.I count
bytes, shorts, or longs using programmed I/O between a memory
.I address
and
.IR port .
Functions
.BI ins x
copy values into memory; functions
.BI outs x
copy values from memory.
The
.I count
is in elements, not bytes.
.SH SOURCE
.B /sys/src/9/pc/l.s
.SH SEE ALSO
.IR dma (10)