Documentation/parport.txt



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The `parport' code provides parallel-port support under Linux.  This
includes the ability to share one port between multiple device
drivers.

You can pass parameters to the parport code to override its automatic
detection of your hardware.  This is particularly useful if you want
to use IRQs, since in general these can't be autoprobed successfully.
By default IRQs are not used even if they _can_ be probed.  This is
because there are a lot of people using the same IRQ for their
parallel port and a sound card or network card.

The parport code is split into two parts: generic (which deals with
port-sharing) and architecture-dependent (which deals with actually
using the port).


Parport as modules
==================

If you load the parport code as a module, say

	# insmod parport

to load the generic parport code.  You then must load the
architecture-dependent code with (for example):

	# insmod parport_pc io=0x3bc,0x378,0x278 irq=none,7,auto

to tell the parport code that you want three PC-style ports, one at
0x3bc with no IRQ, one at 0x378 using IRQ 7, and one at 0x278 with an
auto-detected IRQ.  Currently, PC-style (parport_pc), Sun `bpp',
Amiga, Atari, and MFC3 hardware is supported.

PCI parallel I/O card support comes from parport_pc.  Base I/O
addresses should not be specified for supported PCI cards since they
are automatically detected.


KMod
----

If you use kmod, you will find it useful to edit /etc/modprobe.conf.
Here is an example of the lines that need to be added:

	alias parport_lowlevel parport_pc
	options parport_pc io=0x378,0x278 irq=7,auto

KMod will then automatically load parport_pc (with the options
"io=0x378,0x278 irq=7,auto") whenever a parallel port device driver
(such as lp) is loaded.

Note that these are example lines only!  You shouldn't in general need
to specify any options to parport_pc in order to be able to use a
parallel port.


Parport probe [optional]
-------------

In 2.2 kernels there was a module called parport_probe, which was used
for collecting IEEE 1284 device ID information.  This has now been
enhanced and now lives with the IEEE 1284 support.  When a parallel
port is detected, the devices that are connected to it are analysed,
and information is logged like this:

	parport0: Printer, BJC-210 (Canon)

The probe information is available from files in /proc/sys/dev/parport/.


Parport linked into the kernel statically
=========================================

If you compile the parport code into the kernel, then you can use
kernel boot parameters to get the same effect.  Add something like the
following to your LILO command line:

	parport=0x3bc parport=0x378,7 parport=0x278,auto,nofifo

You can have many `parport=...' statements, one for each port you want
to add.  Adding `parport=0' to the kernel command-line will disable