Root/Documentation/parport.txt

1The `parport' code provides parallel-port support under Linux. This
2includes the ability to share one port between multiple device
3drivers.
4
5You can pass parameters to the parport code to override its automatic
6detection of your hardware. This is particularly useful if you want
7to use IRQs, since in general these can't be autoprobed successfully.
8By default IRQs are not used even if they _can_ be probed. This is
9because there are a lot of people using the same IRQ for their
10parallel port and a sound card or network card.
11
12The parport code is split into two parts: generic (which deals with
13port-sharing) and architecture-dependent (which deals with actually
14using the port).
15
16
17Parport as modules
18==================
19
20If you load the parport code as a module, say
21
22    # insmod parport
23
24to load the generic parport code. You then must load the
25architecture-dependent code with (for example):
26
27    # insmod parport_pc io=0x3bc,0x378,0x278 irq=none,7,auto
28
29to tell the parport code that you want three PC-style ports, one at
300x3bc with no IRQ, one at 0x378 using IRQ 7, and one at 0x278 with an
31auto-detected IRQ. Currently, PC-style (parport_pc), Sun `bpp',
32Amiga, Atari, and MFC3 hardware is supported.
33
34PCI parallel I/O card support comes from parport_pc. Base I/O
35addresses should not be specified for supported PCI cards since they
36are automatically detected.
37
38
39KMod
40----
41
42If you use kmod, you will find it useful to edit /etc/modprobe.conf.
43Here is an example of the lines that need to be added:
44
45    alias parport_lowlevel parport_pc
46    options parport_pc io=0x378,0x278 irq=7,auto
47
48KMod will then automatically load parport_pc (with the options
49"io=0x378,0x278 irq=7,auto") whenever a parallel port device driver
50(such as lp) is loaded.
51
52Note that these are example lines only! You shouldn't in general need
53to specify any options to parport_pc in order to be able to use a
54parallel port.
55
56
57Parport probe [optional]
58-------------
59
60In 2.2 kernels there was a module called parport_probe, which was used
61for collecting IEEE 1284 device ID information. This has now been
62enhanced and now lives with the IEEE 1284 support. When a parallel
63port is detected, the devices that are connected to it are analysed,
64and information is logged like this:
65
66    parport0: Printer, BJC-210 (Canon)
67
68The probe information is available from files in /proc/sys/dev/parport/.
69
70
71Parport linked into the kernel statically
72=========================================
73
74If you compile the parport code into the kernel, then you can use
75kernel boot parameters to get the same effect. Add something like the
76following to your LILO command line:
77
78    parport=0x3bc parport=0x378,7 parport=0x278,auto,nofifo
79
80You can have many `parport=...' statements, one for each port you want
81to add. Adding `parport=0' to the kernel command-line will disable
82parport support entirely. Adding `parport=auto' to the kernel
83command-line will make parport use any IRQ lines or DMA channels that
84it auto-detects.
85
86
87Files in /proc
88==============
89
90If you have configured the /proc filesystem into your kernel, you will
91see a new directory entry: /proc/sys/dev/parport. In there will be a
92directory entry for each parallel port for which parport is
93configured. In each of those directories are a collection of files
94describing that parallel port.
95
96The /proc/sys/dev/parport directory tree looks like:
97
98parport
99|-- default
100| |-- spintime
101| `-- timeslice
102|-- parport0
103| |-- autoprobe
104| |-- autoprobe0
105| |-- autoprobe1
106| |-- autoprobe2
107| |-- autoprobe3
108| |-- devices
109| | |-- active
110| | `-- lp
111| | `-- timeslice
112| |-- base-addr
113| |-- irq
114| |-- dma
115| |-- modes
116| `-- spintime
117`-- parport1
118    |-- autoprobe
119    |-- autoprobe0
120    |-- autoprobe1
121    |-- autoprobe2
122    |-- autoprobe3
123    |-- devices
124    | |-- active
125    | `-- ppa
126    | `-- timeslice
127    |-- base-addr
128    |-- irq
129    |-- dma
130    |-- modes
131    `-- spintime
132
133
134File: Contents:
135
136devices/active A list of the device drivers using that port. A "+"
137        will appear by the name of the device currently using
138        the port (it might not appear against any). The
139        string "none" means that there are no device drivers
140        using that port.
141
142base-addr Parallel port's base address, or addresses if the port
143        has more than one in which case they are separated
144        with tabs. These values might not have any sensible
145        meaning for some ports.
146
147irq Parallel port's IRQ, or -1 if none is being used.
148
149dma Parallel port's DMA channel, or -1 if none is being
150        used.
151
152modes Parallel port's hardware modes, comma-separated,
153        meaning:
154
155        PCSPP PC-style SPP registers are available.
156        TRISTATE Port is bidirectional.
157        COMPAT Hardware acceleration for printers is
158                available and will be used.
159        EPP Hardware acceleration for EPP protocol
160                is available and will be used.
161        ECP Hardware acceleration for ECP protocol
162                is available and will be used.
163        DMA DMA is available and will be used.
164
165        Note that the current implementation will only take
166        advantage of COMPAT and ECP modes if it has an IRQ
167        line to use.
168
169autoprobe Any IEEE-1284 device ID information that has been
170        acquired from the (non-IEEE 1284.3) device.
171
172autoprobe[0-3] IEEE 1284 device ID information retrieved from
173        daisy-chain devices that conform to IEEE 1284.3.
174
175spintime The number of microseconds to busy-loop while waiting
176        for the peripheral to respond. You might find that
177        adjusting this improves performance, depending on your
178        peripherals. This is a port-wide setting, i.e. it
179        applies to all devices on a particular port.
180
181timeslice The number of milliseconds that a device driver is
182        allowed to keep a port claimed for. This is advisory,
183        and driver can ignore it if it must.
184
185default/* The defaults for spintime and timeslice. When a new
186        port is registered, it picks up the default spintime.
187        When a new device is registered, it picks up the
188        default timeslice.
189
190Device drivers
191==============
192
193Once the parport code is initialised, you can attach device drivers to
194specific ports. Normally this happens automatically; if the lp driver
195is loaded it will create one lp device for each port found. You can
196override this, though, by using parameters either when you load the lp
197driver:
198
199    # insmod lp parport=0,2
200
201or on the LILO command line:
202
203    lp=parport0 lp=parport2
204
205Both the above examples would inform lp that you want /dev/lp0 to be
206the first parallel port, and /dev/lp1 to be the _third_ parallel port,
207with no lp device associated with the second port (parport1). Note
208that this is different to the way older kernels worked; there used to
209be a static association between the I/O port address and the device
210name, so /dev/lp0 was always the port at 0x3bc. This is no longer the
211case - if you only have one port, it will default to being /dev/lp0,
212regardless of base address.
213
214Also:
215
216 * If you selected the IEEE 1284 support at compile time, you can say
217   `lp=auto' on the kernel command line, and lp will create devices
218   only for those ports that seem to have printers attached.
219
220 * If you give PLIP the `timid' parameter, either with `plip=timid' on
221   the command line, or with `insmod plip timid=1' when using modules,
222   it will avoid any ports that seem to be in use by other devices.
223
224 * IRQ autoprobing works only for a few port types at the moment.
225
226Reporting printer problems with parport
227=======================================
228
229If you are having problems printing, please go through these steps to
230try to narrow down where the problem area is.
231
232When reporting problems with parport, really you need to give all of
233the messages that parport_pc spits out when it initialises. There are
234several code paths:
235
236o polling
237o interrupt-driven, protocol in software
238o interrupt-driven, protocol in hardware using PIO
239o interrupt-driven, protocol in hardware using DMA
240
241The kernel messages that parport_pc logs give an indication of which
242code path is being used. (They could be a lot better actually..)
243
244For normal printer protocol, having IEEE 1284 modes enabled or not
245should not make a difference.
246
247To turn off the 'protocol in hardware' code paths, disable
248CONFIG_PARPORT_PC_FIFO. Note that when they are enabled they are not
249necessarily _used_; it depends on whether the hardware is available,
250enabled by the BIOS, and detected by the driver.
251
252So, to start with, disable CONFIG_PARPORT_PC_FIFO, and load parport_pc
253with 'irq=none'. See if printing works then. It really should,
254because this is the simplest code path.
255
256If that works fine, try with 'io=0x378 irq=7' (adjust for your
257hardware), to make it use interrupt-driven in-software protocol.
258
259If _that_ works fine, then one of the hardware modes isn't working
260right. Enable CONFIG_PARPORT_PC_FIFO (no, it isn't a module option,
261and yes, it should be), set the port to ECP mode in the BIOS and note
262the DMA channel, and try with:
263
264    io=0x378 irq=7 dma=none (for PIO)
265    io=0x378 irq=7 dma=3 (for DMA)
266--
267philb@gnu.org
268tim@cyberelk.net
269

Archive Download this file



interactive