paride.txt

《嵌入式系统设计与实例开发实验教材二源码》Linux内核移植与编译实验

		Linux and parallel port IDE devices

PARIDE v1.03   (c) 1997-8  Grant Guenther <[e-mail]>

1. Introduction

Owing to the simplicity and near universality of the parallel port interface
to personal computers, many external devices such as portable hard-disk,
CD-ROM, LS-120 and tape drives use the parallel port to connect to their
host computer.  While some devices (notably scanners) use ad-hoc methods
to pass commands and data through the parallel port interface, most 
external devices are actually identical to an internal model, but with
a parallel-port adapter chip added in.  Some of the original parallel port
adapters were little more than mechanisms for multiplexing a SCSI bus.
(The Iomega PPA-3 adapter used in the ZIP drives is an example of this
approach).  Most current designs, however, take a different approach.
The adapter chip reproduces a small ISA or IDE bus in the external device
and the communication protocol provides operations for reading and writing
device registers, as well as data block transfer functions.  Sometimes,
the device being addressed via the parallel cable is a standard SCSI
controller like an NCR 5380.  The "ditto" family of external tape
drives use the ISA replicator to interface a floppy disk controller,
which is then connected to a floppy-tape mechanism.  The vast majority
of external parallel port devices, however, are now based on standard
IDE type devices, which require no intermediate controller.  If one
were to open up a parallel port CD-ROM drive, for instance, one would
find a standard ATAPI CD-ROM drive, a power supply, and a single adapter
that interconnected a standard PC parallel port cable and a standard
IDE cable.  It is usually possible to exchange the CD-ROM device with
any other device using the IDE interface. 

The document describes the support in Linux for parallel port IDE
devices.  It does not cover parallel port SCSI devices, "ditto" tape
drives or scanners.  Many different devices are supported by the 
parallel port IDE subsystem, including:

	MicroSolutions backpack CD-ROM
	MicroSolutions backpack PD/CD
	MicroSolutions backpack hard-drives
	MicroSolutions backpack 8000t tape drive
	SyQuest EZ-135, EZ-230 & SparQ drives
	Avatar Shark
	Imation Superdisk LS-120
	Maxell Superdisk LS-120
	FreeCom Power CD 
	Hewlett-Packard 5GB and 8GB tape drives
	Hewlett-Packard 7100 and 7200 CD-RW drives

as well as most of the clone and no-name products on the market.

To support such a wide range of devices, PARIDE, the parallel port IDE
subsystem, is actually structured in three parts.   There is a base
paride module which provides a registry and some common methods for
accessing the parallel ports.  The second component is a set of 
high-level drivers for each of the different types of supported devices: 

	pd	IDE disk
	pcd	ATAPI CD-ROM
	pf	ATAPI disk
	pt	ATAPI tape
	pg	ATAPI generic

(Currently, the pg driver is only used with CD-R drives).

The high-level drivers function according to the relevant standards.
The third component of PARIDE is a set of low-level protocol drivers
for each of the parallel port IDE adapter chips.  Thanks to the interest
and encouragement of Linux users from many parts of the world, 
support is available for almost all known adapter protocols:

        aten    ATEN EH-100                            (HK)
        bpck    Microsolutions backpack                (US)
        comm    DataStor (old-type) "commuter" adapter (TW)
        dstr    DataStor EP-2000                       (TW)
        epat    Shuttle EPAT                           (UK)
        epia    Shuttle EPIA                           (UK)
	fit2    FIT TD-2000			       (US)
	fit3    FIT TD-3000			       (US)
	friq    Freecom IQ cable                       (DE)
        frpw    Freecom Power                          (DE)
        kbic    KingByte KBIC-951A and KBIC-971A       (TW)
	ktti    KT Technology PHd adapter              (SG)
        on20    OnSpec 90c20                           (US)
        on26    OnSpec 90c26                           (US)


2. Using the PARIDE subsystem

While configuring the Linux kernel, you may choose either to build
the PARIDE drivers into your kernel, or to build them as modules.

In either case, you will need to select "Parallel port IDE device support"
as well as at least one of the high-level drivers and at least one
of the parallel port communication protocols.  If you do not know
what kind of parallel port adapter is used in your drive, you could
begin by checking the file names and any text files on your DOS 
installation floppy.  Alternatively, you can look at the markings on
the adapter chip itself.  That's usually sufficient to identify the
correct device.  

You can actually select all the protocol modules, and allow the PARIDE
subsystem to try them all for you.

For the "brand-name" products listed above, here are the protocol
and high-level drivers that you would use:

	Manufacturer		Model		Driver	Protocol
	
	MicroSolutions		CD-ROM		pcd	bpck
	MicroSolutions		PD drive	pf	bpck
	MicroSolutions		hard-drive	pd	bpck
	MicroSolutions          8000t tape      pt      bpck
	SyQuest			EZ, SparQ	pd	epat
	Imation			Superdisk	pf	epat
	Maxell                  Superdisk       pf      friq
	Avatar			Shark		pd	epat
	FreeCom			CD-ROM		pcd	frpw
	Hewlett-Packard		5GB Tape	pt	epat
	Hewlett-Packard		7200e (CD)	pcd	epat
	Hewlett-Packard		7200e (CD-R)	pg	epat

2.1  Configuring built-in drivers

We recommend that you get to know how the drivers work and how to
configure them as loadable modules, before attempting to compile a
kernel with the drivers built-in.

If you built all of your PARIDE support directly into your kernel,
and you have just a single parallel port IDE device, your kernel should
locate it automatically for you.  If you have more than one device,
you may need to give some command line options to your bootloader
(eg: LILO), how to do that is beyond the scope of this document.

The high-level drivers accept a number of command line parameters, all
of which are documented in the source files in linux/drivers/block/paride.
By default, each driver will automatically try all parallel ports it
can find, and all protocol types that have been installed, until it finds
a parallel port IDE adapter.  Once it finds one, the probe stops.  So,
if you have more than one device, you will need to tell the drivers
how to identify them.  This requires specifying the port address, the
protocol identification number and, for some devices, the drive's
chain ID.  While your system is booting, a number of messages are
displayed on the console.  Like all such messages, they can be
reviewed with the 'dmesg' command.  Among those messages will be
some lines like:

	paride: bpck registered as protocol 0
	paride: epat registered as protocol 1

The numbers will always be the same until you build a new kernel with
different protocol selections.  You should note these numbers as you
will need them to identify the devices.

If you happen to be using a MicroSolutions backpack device, you will
also need to know the unit ID number for each drive.  This is usually
the last two digits of the drive's serial number (but read MicroSolutions'
documentation about this).

As an example, let's assume that you have a MicroSolutions PD/CD drive
with unit ID number 36 connected to the parallel port at 0x378, a SyQuest 
EZ-135 connected to the chained port on the PD/CD drive and also an 
Imation Superdisk connected to port 0x278.  You could give the following 
options on your boot command:

	pd.drive0=0x378,1 pf.drive0=0x278,1 pf.drive1=0x378,0,36

In the last option, pf.drive1 configures device /dev/pf1, the 0x378
is the parallel port base address, the 0 is the protocol registration
number and 36 is the chain ID.

Please note:  while PARIDE will work both with and without the 
PARPORT parallel port sharing system that is included by the
"Parallel port support" option, PARPORT must be included and enabled
if you want to use chains of devices on the same parallel port.

2.2  Loading and configuring PARIDE as modules

It is much faster and simpler to get to understand the PARIDE drivers
if you use them as loadable kernel modules.   

Note 1:  using these drivers with the "kerneld" automatic module loading
system is not recommended for beginners, and is not documented here.  

Note 2:  if you build PARPORT support as a loadable module, PARIDE must
also be built as loadable modules, and PARPORT must be loaded before the
PARIDE modules.

To use PARIDE, you must begin by 

	insmod paride

this loads a base module which provides a registry for the protocols,
among other tasks.

Then, load as many of the protocol modules as you think you might need.
As you load each module, it will register the protocols that it supports,
and print a log message to your kernel log file and your console. For 
example:

	# insmod epat
	paride: epat registered as protocol 0
	# insmod kbic
	paride: k951 registered as protocol 1
        paride: k971 registered as protocol 2

Finally, you can load high-level drivers for each kind of device that
you have connected.  By default, each driver will autoprobe for a single 
device, but you can support up to four similar devices by giving their