outb (1) - Linux Man Pages
outb: access I/O ports
inb, outb, inw, outw, inl, outl - access I/O ports
inb ADDRESS inw ADDRESS inl ADDRESS outb ADDRESS DATA outw ADDRESS DATA outl ADDRESS DATA
inb 0x278 outw 0x440 0xffff
DESCRIPTIONThese commands enable command line and script access directly to I/O ports on PC hardware.
The "inb", "inw" and "inl" commands perform an input (read) operation on the given I/O port, and print the result.
The "outb", "outw" and "outl" commands perform an output (write) operation to the given I/O port, sending the given data. Note that the order of the parameters is ADDRESS DATA.
The size of the operation is selected according to the suffix, with "b" meaning byte, "w" meaning word (16 bits) and "l" meaning long (32 bits).
Port numbers are in the range 0-0xffff. We don't support access to memory mapped devices.
RETURN FROM IN OPERATIONSThe value read from the port by an ``in'' operation is normally printed in decimal.
Use the "--hex" option to print the result as hexadecimal ("0x" prefix is NOT printed).
TYPE AND SIZE OF OPERATIONThe type and size of the operation is normally determined by the name of the command, eg. "inb" is a read operation of 1 byte.
PERMISSIONSYou would normally need to be root or have the "CAP_SYS_RAWIO" capability in order to run these commands.
WARNINGUsing these commands can cause Bad Things to happen to your hardware.
AUTHORSRichard W.M. Jones <rjones @ redhat . com>
COPYRIGHT(C) Copyright 2009 Red Hat Inc., <http://et.redhat.com/~rjones/ioport>.
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.