linux/Documentation/parport.txt
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   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
  39modprobe
  40--------
  41
  42If you use modprobe , you will find it useful to add lines as below to a
  43configuration file in /etc/modprobe.d/ directory:.
  44
  45        alias parport_lowlevel parport_pc
  46        options parport_pc io=0x378,0x278 irq=7,auto
  47
  48modprobe will load parport_pc (with the options "io=0x378,0x278 irq=7,auto")
  49whenever a parallel port device driver (such as lp) is loaded.
  50
  51Note that these are example lines only!  You shouldn't in general need
  52to specify any options to parport_pc in order to be able to use a
  53parallel port.
  54
  55
  56Parport probe [optional]
  57-------------
  58
  59In 2.2 kernels there was a module called parport_probe, which was used
  60for collecting IEEE 1284 device ID information.  This has now been
  61enhanced and now lives with the IEEE 1284 support.  When a parallel
  62port is detected, the devices that are connected to it are analysed,
  63and information is logged like this:
  64
  65        parport0: Printer, BJC-210 (Canon)
  66
  67The probe information is available from files in /proc/sys/dev/parport/.
  68
  69
  70Parport linked into the kernel statically
  71=========================================
  72
  73If you compile the parport code into the kernel, then you can use
  74kernel boot parameters to get the same effect.  Add something like the
  75following to your LILO command line:
  76
  77        parport=0x3bc parport=0x378,7 parport=0x278,auto,nofifo
  78
  79You can have many `parport=...' statements, one for each port you want
  80to add.  Adding `parport=0' to the kernel command-line will disable
  81parport support entirely.  Adding `parport=auto' to the kernel
  82command-line will make parport use any IRQ lines or DMA channels that
  83it auto-detects.
  84
  85
  86Files in /proc
  87==============
  88
  89If you have configured the /proc filesystem into your kernel, you will
  90see a new directory entry: /proc/sys/dev/parport.  In there will be a
  91directory entry for each parallel port for which parport is
  92configured.  In each of those directories are a collection of files
  93describing that parallel port.
  94
  95The /proc/sys/dev/parport directory tree looks like:
  96
  97parport
  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
 133File:           Contents:
 134
 135devices/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
 141base-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
 146irq             Parallel port's IRQ, or -1 if none is being used.
 147
 148dma             Parallel port's DMA channel, or -1 if none is being
 149                used.
 150
 151modes           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
 168autoprobe       Any IEEE-1284 device ID information that has been
 169                acquired from the (non-IEEE 1284.3) device.
 170
 171autoprobe[0-3]  IEEE 1284 device ID information retrieved from
 172                daisy-chain devices that conform to IEEE 1284.3.
 173
 174spintime        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
 180timeslice       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
 184default/*       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
 189Device drivers
 190==============
 191
 192Once the parport code is initialised, you can attach device drivers to
 193specific ports.  Normally this happens automatically; if the lp driver
 194is loaded it will create one lp device for each port found.  You can
 195override this, though, by using parameters either when you load the lp
 196driver:
 197
 198        # insmod lp parport=0,2
 199
 200or on the LILO command line:
 201
 202        lp=parport0 lp=parport2
 203
 204Both the above examples would inform lp that you want /dev/lp0 to be
 205the first parallel port, and /dev/lp1 to be the _third_ parallel port,
 206with no lp device associated with the second port (parport1).  Note
 207that this is different to the way older kernels worked; there used to
 208be a static association between the I/O port address and the device
 209name, so /dev/lp0 was always the port at 0x3bc.  This is no longer the
 210case - if you only have one port, it will default to being /dev/lp0,
 211regardless of base address.
 212
 213Also:
 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
 225Reporting printer problems with parport
 226=======================================
 227
 228If you are having problems printing, please go through these steps to
 229try to narrow down where the problem area is.
 230
 231When reporting problems with parport, really you need to give all of
 232the messages that parport_pc spits out when it initialises.  There are
 233several code paths:
 234
 235o polling
 236o interrupt-driven, protocol in software
 237o interrupt-driven, protocol in hardware using PIO
 238o interrupt-driven, protocol in hardware using DMA
 239
 240The kernel messages that parport_pc logs give an indication of which
 241code path is being used. (They could be a lot better actually..)
 242
 243For normal printer protocol, having IEEE 1284 modes enabled or not
 244should not make a difference.
 245
 246To turn off the 'protocol in hardware' code paths, disable
 247CONFIG_PARPORT_PC_FIFO.  Note that when they are enabled they are not
 248necessarily _used_; it depends on whether the hardware is available,
 249enabled by the BIOS, and detected by the driver.
 250
 251So, to start with, disable CONFIG_PARPORT_PC_FIFO, and load parport_pc
 252with 'irq=none'. See if printing works then.  It really should,
 253because this is the simplest code path.
 254
 255If that works fine, try with 'io=0x378 irq=7' (adjust for your
 256hardware), to make it use interrupt-driven in-software protocol.
 257
 258If _that_ works fine, then one of the hardware modes isn't working
 259right.  Enable CONFIG_PARPORT_PC_FIFO (no, it isn't a module option,
 260and yes, it should be), set the port to ECP mode in the BIOS and note
 261the 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--
 266philb@gnu.org
 267tim@cyberelk.net
 268
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