parport.rst (9500B)
1Parport 2+++++++ 3 4The ``parport`` code provides parallel-port support under Linux. This 5includes the ability to share one port between multiple device 6drivers. 7 8You can pass parameters to the ``parport`` code to override its automatic 9detection of your hardware. This is particularly useful if you want 10to use IRQs, since in general these can't be autoprobed successfully. 11By default IRQs are not used even if they **can** be probed. This is 12because there are a lot of people using the same IRQ for their 13parallel port and a sound card or network card. 14 15The ``parport`` code is split into two parts: generic (which deals with 16port-sharing) and architecture-dependent (which deals with actually 17using the port). 18 19 20Parport as modules 21================== 22 23If you load the `parport`` code as a module, say:: 24 25 # insmod parport 26 27to load the generic ``parport`` code. You then must load the 28architecture-dependent code with (for example):: 29 30 # insmod parport_pc io=0x3bc,0x378,0x278 irq=none,7,auto 31 32to tell the ``parport`` code that you want three PC-style ports, one at 330x3bc with no IRQ, one at 0x378 using IRQ 7, and one at 0x278 with an 34auto-detected IRQ. Currently, PC-style (``parport_pc``), Sun ``bpp``, 35Amiga, Atari, and MFC3 hardware is supported. 36 37PCI parallel I/O card support comes from ``parport_pc``. Base I/O 38addresses should not be specified for supported PCI cards since they 39are automatically detected. 40 41 42modprobe 43-------- 44 45If you use modprobe , you will find it useful to add lines as below to a 46configuration file in /etc/modprobe.d/ directory:: 47 48 alias parport_lowlevel parport_pc 49 options parport_pc io=0x378,0x278 irq=7,auto 50 51modprobe will load ``parport_pc`` (with the options ``io=0x378,0x278 irq=7,auto``) 52whenever a parallel port device driver (such as ``lp``) is loaded. 53 54Note that these are example lines only! You shouldn't in general need 55to specify any options to ``parport_pc`` in order to be able to use a 56parallel port. 57 58 59Parport probe [optional] 60------------------------ 61 62In 2.2 kernels there was a module called ``parport_probe``, which was used 63for collecting IEEE 1284 device ID information. This has now been 64enhanced and now lives with the IEEE 1284 support. When a parallel 65port is detected, the devices that are connected to it are analysed, 66and information is logged like this:: 67 68 parport0: Printer, BJC-210 (Canon) 69 70The probe information is available from files in ``/proc/sys/dev/parport/``. 71 72 73Parport linked into the kernel statically 74========================================= 75 76If you compile the ``parport`` code into the kernel, then you can use 77kernel boot parameters to get the same effect. Add something like the 78following to your LILO command line:: 79 80 parport=0x3bc parport=0x378,7 parport=0x278,auto,nofifo 81 82You can have many ``parport=...`` statements, one for each port you want 83to add. Adding ``parport=0`` to the kernel command-line will disable 84parport support entirely. Adding ``parport=auto`` to the kernel 85command-line will make ``parport`` use any IRQ lines or DMA channels that 86it auto-detects. 87 88 89Files in /proc 90============== 91 92If you have configured the ``/proc`` filesystem into your kernel, you will 93see a new directory entry: ``/proc/sys/dev/parport``. In there will be a 94directory entry for each parallel port for which parport is 95configured. In each of those directories are a collection of files 96describing that parallel port. 97 98The ``/proc/sys/dev/parport`` directory tree looks like:: 99 100 parport 101 |-- default 102 | |-- spintime 103 | `-- timeslice 104 |-- parport0 105 | |-- autoprobe 106 | |-- autoprobe0 107 | |-- autoprobe1 108 | |-- autoprobe2 109 | |-- autoprobe3 110 | |-- devices 111 | | |-- active 112 | | `-- lp 113 | | `-- timeslice 114 | |-- base-addr 115 | |-- irq 116 | |-- dma 117 | |-- modes 118 | `-- spintime 119 `-- parport1 120 |-- autoprobe 121 |-- autoprobe0 122 |-- autoprobe1 123 |-- autoprobe2 124 |-- autoprobe3 125 |-- devices 126 | |-- active 127 | `-- ppa 128 | `-- timeslice 129 |-- base-addr 130 |-- irq 131 |-- dma 132 |-- modes 133 `-- spintime 134 135.. tabularcolumns:: |p{4.0cm}|p{13.5cm}| 136 137======================= ======================================================= 138File Contents 139======================= ======================================================= 140``devices/active`` A list of the device drivers using that port. A "+" 141 will appear by the name of the device currently using 142 the port (it might not appear against any). The 143 string "none" means that there are no device drivers 144 using that port. 145 146``base-addr`` Parallel port's base address, or addresses if the port 147 has more than one in which case they are separated 148 with tabs. These values might not have any sensible 149 meaning for some ports. 150 151``irq`` Parallel port's IRQ, or -1 if none is being used. 152 153``dma`` Parallel port's DMA channel, or -1 if none is being 154 used. 155 156``modes`` Parallel port's hardware modes, comma-separated, 157 meaning: 158 159 - PCSPP 160 PC-style SPP registers are available. 161 162 - TRISTATE 163 Port is bidirectional. 164 165 - COMPAT 166 Hardware acceleration for printers is 167 available and will be used. 168 169 - EPP 170 Hardware acceleration for EPP protocol 171 is available and will be used. 172 173 - ECP 174 Hardware acceleration for ECP protocol 175 is available and will be used. 176 177 - DMA 178 DMA is available and will be used. 179 180 Note that the current implementation will only take 181 advantage of COMPAT and ECP modes if it has an IRQ 182 line to use. 183 184``autoprobe`` Any IEEE-1284 device ID information that has been 185 acquired from the (non-IEEE 1284.3) device. 186 187``autoprobe[0-3]`` IEEE 1284 device ID information retrieved from 188 daisy-chain devices that conform to IEEE 1284.3. 189 190``spintime`` The number of microseconds to busy-loop while waiting 191 for the peripheral to respond. You might find that 192 adjusting this improves performance, depending on your 193 peripherals. This is a port-wide setting, i.e. it 194 applies to all devices on a particular port. 195 196``timeslice`` The number of milliseconds that a device driver is 197 allowed to keep a port claimed for. This is advisory, 198 and driver can ignore it if it must. 199 200``default/*`` The defaults for spintime and timeslice. When a new 201 port is registered, it picks up the default spintime. 202 When a new device is registered, it picks up the 203 default timeslice. 204======================= ======================================================= 205 206Device drivers 207============== 208 209Once the parport code is initialised, you can attach device drivers to 210specific ports. Normally this happens automatically; if the lp driver 211is loaded it will create one lp device for each port found. You can 212override this, though, by using parameters either when you load the lp 213driver:: 214 215 # insmod lp parport=0,2 216 217or on the LILO command line:: 218 219 lp=parport0 lp=parport2 220 221Both the above examples would inform lp that you want ``/dev/lp0`` to be 222the first parallel port, and /dev/lp1 to be the **third** parallel port, 223with no lp device associated with the second port (parport1). Note 224that this is different to the way older kernels worked; there used to 225be a static association between the I/O port address and the device 226name, so ``/dev/lp0`` was always the port at 0x3bc. This is no longer the 227case - if you only have one port, it will default to being ``/dev/lp0``, 228regardless of base address. 229 230Also: 231 232 * If you selected the IEEE 1284 support at compile time, you can say 233 ``lp=auto`` on the kernel command line, and lp will create devices 234 only for those ports that seem to have printers attached. 235 236 * If you give PLIP the ``timid`` parameter, either with ``plip=timid`` on 237 the command line, or with ``insmod plip timid=1`` when using modules, 238 it will avoid any ports that seem to be in use by other devices. 239 240 * IRQ autoprobing works only for a few port types at the moment. 241 242Reporting printer problems with parport 243======================================= 244 245If you are having problems printing, please go through these steps to 246try to narrow down where the problem area is. 247 248When reporting problems with parport, really you need to give all of 249the messages that ``parport_pc`` spits out when it initialises. There are 250several code paths: 251 252- polling 253- interrupt-driven, protocol in software 254- interrupt-driven, protocol in hardware using PIO 255- interrupt-driven, protocol in hardware using DMA 256 257The kernel messages that ``parport_pc`` logs give an indication of which 258code path is being used. (They could be a lot better actually..) 259 260For normal printer protocol, having IEEE 1284 modes enabled or not 261should not make a difference. 262 263To turn off the 'protocol in hardware' code paths, disable 264``CONFIG_PARPORT_PC_FIFO``. Note that when they are enabled they are not 265necessarily **used**; it depends on whether the hardware is available, 266enabled by the BIOS, and detected by the driver. 267 268So, to start with, disable ``CONFIG_PARPORT_PC_FIFO``, and load ``parport_pc`` 269with ``irq=none``. See if printing works then. It really should, 270because this is the simplest code path. 271 272If that works fine, try with ``io=0x378 irq=7`` (adjust for your 273hardware), to make it use interrupt-driven in-software protocol. 274 275If **that** works fine, then one of the hardware modes isn't working 276right. Enable ``CONFIG_FIFO`` (no, it isn't a module option, 277and yes, it should be), set the port to ECP mode in the BIOS and note 278the DMA channel, and try with:: 279 280 io=0x378 irq=7 dma=none (for PIO) 281 io=0x378 irq=7 dma=3 (for DMA) 282 283---------- 284 285philb@gnu.org 286tim@cyberelk.net