Based on kernel version 4.9. Page generated on 2016-12-21 14:36 EST.
1 The `parport' code provides parallel-port support under Linux. This 2 includes the ability to share one port between multiple device 3 drivers. 4 5 You can pass parameters to the parport code to override its automatic 6 detection of your hardware. This is particularly useful if you want 7 to use IRQs, since in general these can't be autoprobed successfully. 8 By default IRQs are not used even if they _can_ be probed. This is 9 because there are a lot of people using the same IRQ for their 10 parallel port and a sound card or network card. 11 12 The parport code is split into two parts: generic (which deals with 13 port-sharing) and architecture-dependent (which deals with actually 14 using the port). 15 16 17 Parport as modules 18 ================== 19 20 If you load the parport code as a module, say 21 22 # insmod parport 23 24 to load the generic parport code. You then must load the 25 architecture-dependent code with (for example): 26 27 # insmod parport_pc io=0x3bc,0x378,0x278 irq=none,7,auto 28 29 to tell the parport code that you want three PC-style ports, one at 30 0x3bc with no IRQ, one at 0x378 using IRQ 7, and one at 0x278 with an 31 auto-detected IRQ. Currently, PC-style (parport_pc), Sun `bpp', 32 Amiga, Atari, and MFC3 hardware is supported. 33 34 PCI parallel I/O card support comes from parport_pc. Base I/O 35 addresses should not be specified for supported PCI cards since they 36 are automatically detected. 37 38 39 modprobe 40 -------- 41 42 If you use modprobe , you will find it useful to add lines as below to a 43 configuration file in /etc/modprobe.d/ directory:. 44 45 alias parport_lowlevel parport_pc 46 options parport_pc io=0x378,0x278 irq=7,auto 47 48 modprobe will load parport_pc (with the options "io=0x378,0x278 irq=7,auto") 49 whenever a parallel port device driver (such as lp) is loaded. 50 51 Note that these are example lines only! You shouldn't in general need 52 to specify any options to parport_pc in order to be able to use a 53 parallel port. 54 55 56 Parport probe [optional] 57 ------------- 58 59 In 2.2 kernels there was a module called parport_probe, which was used 60 for collecting IEEE 1284 device ID information. This has now been 61 enhanced and now lives with the IEEE 1284 support. When a parallel 62 port is detected, the devices that are connected to it are analysed, 63 and information is logged like this: 64 65 parport0: Printer, BJC-210 (Canon) 66 67 The probe information is available from files in /proc/sys/dev/parport/. 68 69 70 Parport linked into the kernel statically 71 ========================================= 72 73 If you compile the parport code into the kernel, then you can use 74 kernel boot parameters to get the same effect. Add something like the 75 following to your LILO command line: 76 77 parport=0x3bc parport=0x378,7 parport=0x278,auto,nofifo 78 79 You can have many `parport=...' statements, one for each port you want 80 to add. Adding `parport=0' to the kernel command-line will disable 81 parport support entirely. Adding `parport=auto' to the kernel 82 command-line will make parport use any IRQ lines or DMA channels that 83 it auto-detects. 84 85 86 Files in /proc 87 ============== 88 89 If you have configured the /proc filesystem into your kernel, you will 90 see a new directory entry: /proc/sys/dev/parport. In there will be a 91 directory entry for each parallel port for which parport is 92 configured. In each of those directories are a collection of files 93 describing that parallel port. 94 95 The /proc/sys/dev/parport directory tree looks like: 96 97 parport 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 131 132 133 File: Contents: 134 135 devices/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. 140 141 base-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. 145 146 irq Parallel port's IRQ, or -1 if none is being used. 147 148 dma Parallel port's DMA channel, or -1 if none is being 149 used. 150 151 modes 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. 167 168 autoprobe Any IEEE-1284 device ID information that has been 169 acquired from the (non-IEEE 1284.3) device. 170 171 autoprobe[0-3] IEEE 1284 device ID information retrieved from 172 daisy-chain devices that conform to IEEE 1284.3. 173 174 spintime 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. 179 180 timeslice 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. 183 184 default/* 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. 188 189 Device drivers 190 ============== 191 192 Once the parport code is initialised, you can attach device drivers to 193 specific ports. Normally this happens automatically; if the lp driver 194 is loaded it will create one lp device for each port found. You can 195 override this, though, by using parameters either when you load the lp 196 driver: 197 198 # insmod lp parport=0,2 199 200 or on the LILO command line: 201 202 lp=parport0 lp=parport2 203 204 Both the above examples would inform lp that you want /dev/lp0 to be 205 the first parallel port, and /dev/lp1 to be the _third_ parallel port, 206 with no lp device associated with the second port (parport1). Note 207 that this is different to the way older kernels worked; there used to 208 be a static association between the I/O port address and the device 209 name, so /dev/lp0 was always the port at 0x3bc. This is no longer the 210 case - if you only have one port, it will default to being /dev/lp0, 211 regardless of base address. 212 213 Also: 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. 224 225 Reporting printer problems with parport 226 ======================================= 227 228 If you are having problems printing, please go through these steps to 229 try to narrow down where the problem area is. 230 231 When reporting problems with parport, really you need to give all of 232 the messages that parport_pc spits out when it initialises. There are 233 several code paths: 234 235 o polling 236 o interrupt-driven, protocol in software 237 o interrupt-driven, protocol in hardware using PIO 238 o interrupt-driven, protocol in hardware using DMA 239 240 The kernel messages that parport_pc logs give an indication of which 241 code path is being used. (They could be a lot better actually..) 242 243 For normal printer protocol, having IEEE 1284 modes enabled or not 244 should not make a difference. 245 246 To turn off the 'protocol in hardware' code paths, disable 247 CONFIG_PARPORT_PC_FIFO. Note that when they are enabled they are not 248 necessarily _used_; it depends on whether the hardware is available, 249 enabled by the BIOS, and detected by the driver. 250 251 So, to start with, disable CONFIG_PARPORT_PC_FIFO, and load parport_pc 252 with 'irq=none'. See if printing works then. It really should, 253 because this is the simplest code path. 254 255 If that works fine, try with 'io=0x378 irq=7' (adjust for your 256 hardware), to make it use interrupt-driven in-software protocol. 257 258 If _that_ works fine, then one of the hardware modes isn't working 259 right. Enable CONFIG_PARPORT_PC_FIFO (no, it isn't a module option, 260 and yes, it should be), set the port to ECP mode in the BIOS and note 261 the 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 -- 266 philb@gnu.org 267 tim@cyberelk.net
