1 Parport
2 +++++++
3
4 The ``parport`` code provides parallel-port support under Linux. This
5 includes the ability to share one port between multiple device
6 drivers.
7
8 You can pass parameters to the ``parport`` code to override its automatic
9 detection of your hardware. This is particularly useful if you want
10 to use IRQs, since in general these can't be autoprobed successfully.
11 By default IRQs are not used even if they **can** be probed. This is
12 because there are a lot of people using the same IRQ for their
13 parallel port and a sound card or network card.
14
15 The ``parport`` code is split into two parts: generic (which deals with
16 port-sharing) and architecture-dependent (which deals with actually
17 using the port).
18
19
20 Parport as modules
21 ==================
22
23 If you load the `parport`` code as a module, say::
24
25 # insmod parport
26
27 to load the generic ``parport`` code. You then must load the
28 architecture-dependent code with (for example)::
29
30 # insmod parport_pc io=0x3bc,0x378,0x278 irq=none,7,auto
31
32 to tell the ``parport`` code that you want three PC-style ports, one at
33 0x3bc with no IRQ, one at 0x378 using IRQ 7, and one at 0x278 with an
34 auto-detected IRQ. Currently, PC-style (``parport_pc``), Sun ``bpp``,
35 Amiga, Atari, and MFC3 hardware is supported.
36
37 PCI parallel I/O card support comes from ``parport_pc``. Base I/O
38 addresses should not be specified for supported PCI cards since they
39 are automatically detected.
40
41
42 modprobe
43 --------
44
45 If you use modprobe , you will find it useful to add lines as below to a
46 configuration file in /etc/modprobe.d/ directory::
47
48 alias parport_lowlevel parport_pc
49 options parport_pc io=0x378,0x278 irq=7,auto
50
51 modprobe will load ``parport_pc`` (with the options ``io=0x378,0x278 irq=7,auto``)
52 whenever a parallel port device driver (such as ``lp``) is loaded.
53
54 Note that these are example lines only! You shouldn't in general need
55 to specify any options to ``parport_pc`` in order to be able to use a
56 parallel port.
57
58
59 Parport probe [optional]
60 ------------------------
61
62 In 2.2 kernels there was a module called ``parport_probe``, which was used
63 for collecting IEEE 1284 device ID information. This has now been
64 enhanced and now lives with the IEEE 1284 support. When a parallel
65 port is detected, the devices that are connected to it are analysed,
66 and information is logged like this::
67
68 parport0: Printer, BJC-210 (Canon)
69
70 The probe information is available from files in ``/proc/sys/dev/parport/``.
71
72
73 Parport linked into the kernel statically
74 =========================================
75
76 If you compile the ``parport`` code into the kernel, then you can use
77 kernel boot parameters to get the same effect. Add something like the
78 following to your LILO command line::
79
80 parport=0x3bc parport=0x378,7 parport=0x278,auto,nofifo
81
82 You can have many ``parport=...`` statements, one for each port you want
83 to add. Adding ``parport=0`` to the kernel command-line will disable
84 parport support entirely. Adding ``parport=auto`` to the kernel
85 command-line will make ``parport`` use any IRQ lines or DMA channels that
86 it auto-detects.
87
88
89 Files in /proc
90 ==============
91
92 If you have configured the ``/proc`` filesystem into your kernel, you will
93 see a new directory entry: ``/proc/sys/dev/parport``. In there will be a
94 directory entry for each parallel port for which parport is
95 configured. In each of those directories are a collection of files
96 describing that parallel port.
97
98 The ``/proc/sys/dev/parport`` directory tree looks like::
99
100 parport
101 |-- default
102 | |-- spintime
103 | `-- timeslice
104 |-- parport0
105 | |-- autoprobe
106 | |-- autoprobe0
107 | |-- autoprobe1
108 | |-- autoprobe2
109 | |-- autoprobe3
110 | |-- devices
111 | | |-- active
112 | | `-- lp
113 | | `-- timeslice
114 | |-- base-addr
115 | |-- irq
116 | |-- dma
117 | |-- modes
118 | `-- spintime
119 `-- parport1
120 |-- autoprobe
121 |-- autoprobe0
122 |-- autoprobe1
123 |-- autoprobe2
124 |-- autoprobe3
125 |-- devices
126 | |-- active
127 | `-- ppa
128 | `-- timeslice
129 |-- base-addr
130 |-- irq
131 |-- dma
132 |-- modes
133 `-- spintime
134
135 .. tabularcolumns:: |p{4.0cm}|p{13.5cm}|
136
137 ======================= =======================================================
138 File Contents
139 ======================= =======================================================
140 ``devices/active`` A list of the device drivers using that port. A "+"
141 will appear by the name of the device currently using
142 the port (it might not appear against any). The
143 string "none" means that there are no device drivers
144 using that port.
145
146 ``base-addr`` Parallel port's base address, or addresses if the port
147 has more than one in which case they are separated
148 with tabs. These values might not have any sensible
149 meaning for some ports.
150
151 ``irq`` Parallel port's IRQ, or -1 if none is being used.
152
153 ``dma`` Parallel port's DMA channel, or -1 if none is being
154 used.
155
156 ``modes`` Parallel port's hardware modes, comma-separated,
157 meaning:
158
159 - PCSPP
160 PC-style SPP registers are available.
161
162 - TRISTATE
163 Port is bidirectional.
164
165 - COMPAT
166 Hardware acceleration for printers is
167 available and will be used.
168
169 - EPP
170 Hardware acceleration for EPP protocol
171 is available and will be used.
172
173 - ECP
174 Hardware acceleration for ECP protocol
175 is available and will be used.
176
177 - DMA
178 DMA is available and will be used.
179
180 Note that the current implementation will only take
181 advantage of COMPAT and ECP modes if it has an IRQ
182 line to use.
183
184 ``autoprobe`` Any IEEE-1284 device ID information that has been
185 acquired from the (non-IEEE 1284.3) device.
186
187 ``autoprobe[0-3]`` IEEE 1284 device ID information retrieved from
188 daisy-chain devices that conform to IEEE 1284.3.
189
190 ``spintime`` The number of microseconds to busy-loop while waiting
191 for the peripheral to respond. You might find that
192 adjusting this improves performance, depending on your
193 peripherals. This is a port-wide setting, i.e. it
194 applies to all devices on a particular port.
195
196 ``timeslice`` The number of milliseconds that a device driver is
197 allowed to keep a port claimed for. This is advisory,
198 and driver can ignore it if it must.
199
200 ``default/*`` The defaults for spintime and timeslice. When a new
201 port is registered, it picks up the default spintime.
202 When a new device is registered, it picks up the
203 default timeslice.
204 ======================= =======================================================
205
206 Device drivers
207 ==============
208
209 Once the parport code is initialised, you can attach device drivers to
210 specific ports. Normally this happens automatically; if the lp driver
211 is loaded it will create one lp device for each port found. You can
212 override this, though, by using parameters either when you load the lp
213 driver::
214
215 # insmod lp parport=0,2
216
217 or on the LILO command line::
218
219 lp=parport0 lp=parport2
220
221 Both the above examples would inform lp that you want ``/dev/lp0`` to be
222 the first parallel port, and /dev/lp1 to be the **third** parallel port,
223 with no lp device associated with the second port (parport1). Note
224 that this is different to the way older kernels worked; there used to
225 be a static association between the I/O port address and the device
226 name, so ``/dev/lp0`` was always the port at 0x3bc. This is no longer the
227 case - if you only have one port, it will default to being ``/dev/lp0``,
228 regardless of base address.
229
230 Also:
231
232 * If you selected the IEEE 1284 support at compile time, you can say
233 ``lp=auto`` on the kernel command line, and lp will create devices
234 only for those ports that seem to have printers attached.
235
236 * If you give PLIP the ``timid`` parameter, either with ``plip=timid`` on
237 the command line, or with ``insmod plip timid=1`` when using modules,
238 it will avoid any ports that seem to be in use by other devices.
239
240 * IRQ autoprobing works only for a few port types at the moment.
241
242 Reporting printer problems with parport
243 =======================================
244
245 If you are having problems printing, please go through these steps to
246 try to narrow down where the problem area is.
247
248 When reporting problems with parport, really you need to give all of
249 the messages that ``parport_pc`` spits out when it initialises. There are
250 several code paths:
251
252 - polling
253 - interrupt-driven, protocol in software
254 - interrupt-driven, protocol in hardware using PIO
255 - interrupt-driven, protocol in hardware using DMA
256
257 The kernel messages that ``parport_pc`` logs give an indication of which
258 code path is being used. (They could be a lot better actually..)
259
260 For normal printer protocol, having IEEE 1284 modes enabled or not
261 should not make a difference.
262
263 To turn off the 'protocol in hardware' code paths, disable
264 ``CONFIG_PARPORT_PC_FIFO``. Note that when they are enabled they are not
265 necessarily **used**; it depends on whether the hardware is available,
266 enabled by the BIOS, and detected by the driver.
267
268 So, to start with, disable ``CONFIG_PARPORT_PC_FIFO``, and load ``parport_pc``
269 with ``irq=none``. See if printing works then. It really should,
270 because this is the simplest code path.
271
272 If that works fine, try with ``io=0x378 irq=7`` (adjust for your
273 hardware), to make it use interrupt-driven in-software protocol.
274
275 If **that** works fine, then one of the hardware modes isn't working
276 right. Enable ``CONFIG_FIFO`` (no, it isn't a module option,
277 and yes, it should be), set the port to ECP mode in the BIOS and note
278 the DMA channel, and try with::
279
280 io=0x378 irq=7 dma=none (for PIO)
281 io=0x378 irq=7 dma=3 (for DMA)
282
283 ----------
284
285 philb@gnu.org
286 tim@cyberelk.net
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