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Based on kernel version 3.16. Page generated on 2014-08-06 21:40 EST.

1	The `parport' code provides parallel-port support under Linux.  This
2	includes the ability to share one port between multiple device
3	drivers.
4	
5	You can pass parameters to the parport code to override its automatic
6	detection of your hardware.  This is particularly useful if you want
7	to use IRQs, since in general these can't be autoprobed successfully.
8	By default IRQs are not used even if they _can_ be probed.  This is
9	because there are a lot of people using the same IRQ for their
10	parallel port and a sound card or network card.
11	
12	The parport code is split into two parts: generic (which deals with
13	port-sharing) and architecture-dependent (which deals with actually
14	using the port).
15	
16	
17	Parport as modules
18	==================
19	
20	If you load the parport code as a module, say
21	
22		# insmod parport
23	
24	to load the generic parport code.  You then must load the
25	architecture-dependent code with (for example):
26	
27		# insmod parport_pc io=0x3bc,0x378,0x278 irq=none,7,auto
28	
29	to tell the parport code that you want three PC-style ports, one at
30	0x3bc with no IRQ, one at 0x378 using IRQ 7, and one at 0x278 with an
31	auto-detected IRQ.  Currently, PC-style (parport_pc), Sun `bpp',
32	Amiga, Atari, and MFC3 hardware is supported.
33	
34	PCI parallel I/O card support comes from parport_pc.  Base I/O
35	addresses should not be specified for supported PCI cards since they
36	are automatically detected.
37	
38	
39	modprobe
40	--------
41	
42	If you use modprobe , you will find it useful to add lines as below to a
43	configuration file in /etc/modprobe.d/ directory:.
44	
45		alias parport_lowlevel parport_pc
46		options parport_pc io=0x378,0x278 irq=7,auto
47	
48	modprobe will load parport_pc (with the options "io=0x378,0x278 irq=7,auto")
49	whenever a parallel port device driver (such as lp) is loaded.
50	
51	Note that these are example lines only!  You shouldn't in general need
52	to specify any options to parport_pc in order to be able to use a
53	parallel port.
54	
55	
56	Parport probe [optional]
57	-------------
58	
59	In 2.2 kernels there was a module called parport_probe, which was used
60	for collecting IEEE 1284 device ID information.  This has now been
61	enhanced and now lives with the IEEE 1284 support.  When a parallel
62	port is detected, the devices that are connected to it are analysed,
63	and information is logged like this:
64	
65		parport0: Printer, BJC-210 (Canon)
66	
67	The probe information is available from files in /proc/sys/dev/parport/.
68	
69	
70	Parport linked into the kernel statically
71	=========================================
72	
73	If you compile the parport code into the kernel, then you can use
74	kernel boot parameters to get the same effect.  Add something like the
75	following to your LILO command line:
76	
77		parport=0x3bc parport=0x378,7 parport=0x278,auto,nofifo
78	
79	You can have many `parport=...' statements, one for each port you want
80	to add.  Adding `parport=0' to the kernel command-line will disable
81	parport support entirely.  Adding `parport=auto' to the kernel
82	command-line will make parport use any IRQ lines or DMA channels that
83	it auto-detects.
84	
85	
86	Files in /proc
87	==============
88	
89	If you have configured the /proc filesystem into your kernel, you will
90	see a new directory entry: /proc/sys/dev/parport.  In there will be a
91	directory entry for each parallel port for which parport is
92	configured.  In each of those directories are a collection of files
93	describing that parallel port.
94	
95	The /proc/sys/dev/parport directory tree looks like:
96	
97	parport
98	|-- default
99	|   |-- spintime
100	|   `-- timeslice
101	|-- parport0
102	|   |-- autoprobe
103	|   |-- autoprobe0
104	|   |-- autoprobe1
105	|   |-- autoprobe2
106	|   |-- autoprobe3
107	|   |-- devices
108	|   |   |-- active
109	|   |   `-- lp
110	|   |       `-- timeslice
111	|   |-- base-addr
112	|   |-- irq
113	|   |-- dma
114	|   |-- modes
115	|   `-- spintime
116	`-- parport1
117	    |-- autoprobe
118	    |-- autoprobe0
119	    |-- autoprobe1
120	    |-- autoprobe2
121	    |-- autoprobe3
122	    |-- devices
123	    |   |-- active
124	    |   `-- ppa
125	    |       `-- timeslice
126	    |-- base-addr
127	    |-- irq
128	    |-- dma
129	    |-- modes
130	    `-- spintime
131	
132	
133	File:		Contents:
134	
135	devices/active	A list of the device drivers using that port.  A "+"
136			will appear by the name of the device currently using
137			the port (it might not appear against any).  The
138			string "none" means that there are no device drivers
139			using that port.
140	
141	base-addr	Parallel port's base address, or addresses if the port
142			has more than one in which case they are separated
143			with tabs.  These values might not have any sensible
144			meaning for some ports.
145	
146	irq		Parallel port's IRQ, or -1 if none is being used.
147	
148	dma		Parallel port's DMA channel, or -1 if none is being
149			used.
150	
151	modes		Parallel port's hardware modes, comma-separated,
152			meaning:
153	
154			PCSPP		PC-style SPP registers are available.
155			TRISTATE	Port is bidirectional.
156			COMPAT		Hardware acceleration for printers is
157					available and will be used.
158			EPP		Hardware acceleration for EPP protocol
159					is available and will be used.
160			ECP		Hardware acceleration for ECP protocol
161					is available and will be used.
162			DMA		DMA is available and will be used.
163	
164			Note that the current implementation will only take
165			advantage of COMPAT and ECP modes if it has an IRQ
166			line to use.
167	
168	autoprobe	Any IEEE-1284 device ID information that has been
169			acquired from the (non-IEEE 1284.3) device.
170	
171	autoprobe[0-3]	IEEE 1284 device ID information retrieved from
172			daisy-chain devices that conform to IEEE 1284.3.
173	
174	spintime	The number of microseconds to busy-loop while waiting
175			for the peripheral to respond.  You might find that
176			adjusting this improves performance, depending on your
177			peripherals.  This is a port-wide setting, i.e. it
178			applies to all devices on a particular port.
179	
180	timeslice	The number of milliseconds that a device driver is
181			allowed to keep a port claimed for.  This is advisory,
182			and driver can ignore it if it must.
183	
184	default/*	The defaults for spintime and timeslice. When a new
185			port is	registered, it picks up the default spintime.
186			When a new device is registered, it picks up the
187			default timeslice.
188	
189	Device drivers
190	==============
191	
192	Once the parport code is initialised, you can attach device drivers to
193	specific ports.  Normally this happens automatically; if the lp driver
194	is loaded it will create one lp device for each port found.  You can
195	override this, though, by using parameters either when you load the lp
196	driver:
197	
198		# insmod lp parport=0,2
199	
200	or on the LILO command line:
201	
202		lp=parport0 lp=parport2
203	
204	Both the above examples would inform lp that you want /dev/lp0 to be
205	the first parallel port, and /dev/lp1 to be the _third_ parallel port,
206	with no lp device associated with the second port (parport1).  Note
207	that this is different to the way older kernels worked; there used to
208	be a static association between the I/O port address and the device
209	name, so /dev/lp0 was always the port at 0x3bc.  This is no longer the
210	case - if you only have one port, it will default to being /dev/lp0,
211	regardless of base address.
212	
213	Also:
214	
215	 * If you selected the IEEE 1284 support at compile time, you can say
216	   `lp=auto' on the kernel command line, and lp will create devices
217	   only for those ports that seem to have printers attached.
218	
219	 * If you give PLIP the `timid' parameter, either with `plip=timid' on
220	   the command line, or with `insmod plip timid=1' when using modules,
221	   it will avoid any ports that seem to be in use by other devices.
222	
223	 * IRQ autoprobing works only for a few port types at the moment.
224	
225	Reporting printer problems with parport
226	=======================================
227	
228	If you are having problems printing, please go through these steps to
229	try to narrow down where the problem area is.
230	
231	When reporting problems with parport, really you need to give all of
232	the messages that parport_pc spits out when it initialises.  There are
233	several code paths:
234	
235	o polling
236	o interrupt-driven, protocol in software
237	o interrupt-driven, protocol in hardware using PIO
238	o interrupt-driven, protocol in hardware using DMA
239	
240	The kernel messages that parport_pc logs give an indication of which
241	code path is being used. (They could be a lot better actually..)
242	
243	For normal printer protocol, having IEEE 1284 modes enabled or not
244	should not make a difference.
245	
246	To turn off the 'protocol in hardware' code paths, disable
247	CONFIG_PARPORT_PC_FIFO.  Note that when they are enabled they are not
248	necessarily _used_; it depends on whether the hardware is available,
249	enabled by the BIOS, and detected by the driver.
250	
251	So, to start with, disable CONFIG_PARPORT_PC_FIFO, and load parport_pc
252	with 'irq=none'. See if printing works then.  It really should,
253	because this is the simplest code path.
254	
255	If that works fine, try with 'io=0x378 irq=7' (adjust for your
256	hardware), to make it use interrupt-driven in-software protocol.
257	
258	If _that_ works fine, then one of the hardware modes isn't working
259	right.  Enable CONFIG_PARPORT_PC_FIFO (no, it isn't a module option,
260	and yes, it should be), set the port to ECP mode in the BIOS and note
261	the DMA channel, and try with:
262	
263	    io=0x378 irq=7 dma=none (for PIO)
264	    io=0x378 irq=7 dma=3 (for DMA)
265	--
266	philb@gnu.org
267	tim@cyberelk.net
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