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diff --git a/Documentation/parport.txt b/Documentation/parport.txt new file mode 100644 index 00000000000..93a7ceef398 --- /dev/null +++ b/Documentation/parport.txt @@ -0,0 +1,268 @@ +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. + + +KMod +---- + +If you use kmod, you will find it useful to edit /etc/modprobe.conf. +Here is an example of the lines that need to be added: + + alias parport_lowlevel parport_pc + options parport_pc io=0x378,0x278 irq=7,auto + +KMod will then automatically 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 |