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-The `parport' code provides parallel-port support under Linux. This
-includes the ability to share one port between multiple device
-drivers.
-
-You can pass parameters to the parport code to override its automatic
-detection of your hardware. This is particularly useful if you want
-to use IRQs, since in general these can't be autoprobed successfully.
-By default IRQs are not used even if they _can_ be probed. This is
-because there are a lot of people using the same IRQ for their
-parallel port and a sound card or network card.
-
-The parport code is split into two parts: generic (which deals with
-port-sharing) and architecture-dependent (which deals with actually
-using the port).
-
-
-Parport as modules
-==================
-
-If you load the parport code as a module, say
-
- # insmod parport
-
-to load the generic parport code. You then must load the
-architecture-dependent code with (for example):
-
- # insmod parport_pc io=0x3bc,0x378,0x278 irq=none,7,auto
-
-to tell the parport code that you want three PC-style ports, one at
-0x3bc with no IRQ, one at 0x378 using IRQ 7, and one at 0x278 with an
-auto-detected IRQ. Currently, PC-style (parport_pc), Sun `bpp',
-Amiga, Atari, and MFC3 hardware is supported.
-
-PCI parallel I/O card support comes from parport_pc. Base I/O
-addresses should not be specified for supported PCI cards since they
-are automatically detected.
-
-
-modprobe
---------
-
-If you use modprobe , you will find it useful to add lines as below to a
-configuration file in /etc/modprobe.d/ directory:.
-
- alias parport_lowlevel parport_pc
- options parport_pc io=0x378,0x278 irq=7,auto
-
-modprobe will load parport_pc (with the options "io=0x378,0x278 irq=7,auto")
-whenever a parallel port device driver (such as lp) is loaded.
-
-Note that these are example lines only! You shouldn't in general need
-to specify any options to parport_pc in order to be able to use a
-parallel port.
-
-
-Parport probe [optional]
--------------
-
-In 2.2 kernels there was a module called parport_probe, which was used
-for collecting IEEE 1284 device ID information. This has now been
-enhanced and now lives with the IEEE 1284 support. When a parallel
-port is detected, the devices that are connected to it are analysed,
-and information is logged like this:
-
- parport0: Printer, BJC-210 (Canon)
-
-The probe information is available from files in /proc/sys/dev/parport/.
-
-
-Parport linked into the kernel statically
-=========================================
-
-If you compile the parport code into the kernel, then you can use
-kernel boot parameters to get the same effect. Add something like the
-following to your LILO command line:
-
- parport=0x3bc parport=0x378,7 parport=0x278,auto,nofifo
-
-You can have many `parport=...' statements, one for each port you want
-to add. Adding `parport=0' to the kernel command-line will disable
-parport support entirely. Adding `parport=auto' to the kernel
-command-line will make parport use any IRQ lines or DMA channels that
-it auto-detects.
-
-
-Files in /proc
-==============
-
-If you have configured the /proc filesystem into your kernel, you will
-see a new directory entry: /proc/sys/dev/parport. In there will be a
-directory entry for each parallel port for which parport is
-configured. In each of those directories are a collection of files
-describing that parallel port.
-
-The /proc/sys/dev/parport directory tree looks like:
-
-parport
-|-- default
-| |-- spintime
-| `-- timeslice
-|-- parport0
-| |-- autoprobe
-| |-- autoprobe0
-| |-- autoprobe1
-| |-- autoprobe2
-| |-- autoprobe3
-| |-- devices
-| | |-- active
-| | `-- lp
-| | `-- timeslice
-| |-- base-addr
-| |-- irq
-| |-- dma
-| |-- modes
-| `-- spintime
-`-- parport1
- |-- autoprobe
- |-- autoprobe0
- |-- autoprobe1
- |-- autoprobe2
- |-- autoprobe3
- |-- devices
- | |-- active
- | `-- ppa
- | `-- timeslice
- |-- base-addr
- |-- irq
- |-- dma
- |-- modes
- `-- spintime
-
-
-File: Contents:
-
-devices/active A list of the device drivers using that port. A "+"
- will appear by the name of the device currently using
- the port (it might not appear against any). The
- string "none" means that there are no device drivers
- using that port.
-
-base-addr Parallel port's base address, or addresses if the port
- has more than one in which case they are separated
- with tabs. These values might not have any sensible
- meaning for some ports.
-
-irq Parallel port's IRQ, or -1 if none is being used.
-
-dma Parallel port's DMA channel, or -1 if none is being
- used.
-
-modes Parallel port's hardware modes, comma-separated,
- meaning:
-
- PCSPP PC-style SPP registers are available.
- TRISTATE Port is bidirectional.
- COMPAT Hardware acceleration for printers is
- available and will be used.
- EPP Hardware acceleration for EPP protocol
- is available and will be used.
- ECP Hardware acceleration for ECP protocol
- is available and will be used.
- DMA DMA is available and will be used.
-
- Note that the current implementation will only take
- advantage of COMPAT and ECP modes if it has an IRQ
- line to use.
-
-autoprobe Any IEEE-1284 device ID information that has been
- acquired from the (non-IEEE 1284.3) device.
-
-autoprobe[0-3] IEEE 1284 device ID information retrieved from
- daisy-chain devices that conform to IEEE 1284.3.
-
-spintime The number of microseconds to busy-loop while waiting
- for the peripheral to respond. You might find that
- adjusting this improves performance, depending on your
- peripherals. This is a port-wide setting, i.e. it
- applies to all devices on a particular port.
-
-timeslice The number of milliseconds that a device driver is
- allowed to keep a port claimed for. This is advisory,
- and driver can ignore it if it must.
-
-default/* The defaults for spintime and timeslice. When a new
- port is registered, it picks up the default spintime.
- When a new device is registered, it picks up the
- default timeslice.
-
-Device drivers
-==============
-
-Once the parport code is initialised, you can attach device drivers to
-specific ports. Normally this happens automatically; if the lp driver
-is loaded it will create one lp device for each port found. You can
-override this, though, by using parameters either when you load the lp
-driver:
-
- # insmod lp parport=0,2
-
-or on the LILO command line:
-
- lp=parport0 lp=parport2
-
-Both the above examples would inform lp that you want /dev/lp0 to be
-the first parallel port, and /dev/lp1 to be the _third_ parallel port,
-with no lp device associated with the second port (parport1). Note
-that this is different to the way older kernels worked; there used to
-be a static association between the I/O port address and the device
-name, so /dev/lp0 was always the port at 0x3bc. This is no longer the
-case - if you only have one port, it will default to being /dev/lp0,
-regardless of base address.
-
-Also:
-
- * If you selected the IEEE 1284 support at compile time, you can say
- `lp=auto' on the kernel command line, and lp will create devices
- only for those ports that seem to have printers attached.
-
- * If you give PLIP the `timid' parameter, either with `plip=timid' on
- the command line, or with `insmod plip timid=1' when using modules,
- it will avoid any ports that seem to be in use by other devices.
-
- * IRQ autoprobing works only for a few port types at the moment.
-
-Reporting printer problems with parport
-=======================================
-
-If you are having problems printing, please go through these steps to
-try to narrow down where the problem area is.
-
-When reporting problems with parport, really you need to give all of
-the messages that parport_pc spits out when it initialises. There are
-several code paths:
-
-o polling
-o interrupt-driven, protocol in software
-o interrupt-driven, protocol in hardware using PIO
-o interrupt-driven, protocol in hardware using DMA
-
-The kernel messages that parport_pc logs give an indication of which
-code path is being used. (They could be a lot better actually..)
-
-For normal printer protocol, having IEEE 1284 modes enabled or not
-should not make a difference.
-
-To turn off the 'protocol in hardware' code paths, disable
-CONFIG_PARPORT_PC_FIFO. Note that when they are enabled they are not
-necessarily _used_; it depends on whether the hardware is available,
-enabled by the BIOS, and detected by the driver.
-
-So, to start with, disable CONFIG_PARPORT_PC_FIFO, and load parport_pc
-with 'irq=none'. See if printing works then. It really should,
-because this is the simplest code path.
-
-If that works fine, try with 'io=0x378 irq=7' (adjust for your
-hardware), to make it use interrupt-driven in-software protocol.
-
-If _that_ works fine, then one of the hardware modes isn't working
-right. Enable CONFIG_PARPORT_PC_FIFO (no, it isn't a module option,
-and yes, it should be), set the port to ECP mode in the BIOS and note
-the DMA channel, and try with:
-
- io=0x378 irq=7 dma=none (for PIO)
- io=0x378 irq=7 dma=3 (for DMA)
---
-philb@gnu.org
-tim@cyberelk.net