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diff --git a/Documentation/admin-guide/parport.rst b/Documentation/admin-guide/parport.rst new file mode 100644 index 000000000000..ad3f9b8a11e1 --- /dev/null +++ b/Documentation/admin-guide/parport.rst @@ -0,0 +1,286 @@ +Parport ++++++++ + +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 + +.. tabularcolumns:: |p{4.0cm}|p{13.5cm}| + +======================= ======================================================= +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: + +- polling +- interrupt-driven, protocol in software +- interrupt-driven, protocol in hardware using PIO +- 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_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 |