Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame^] | 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 | KMod |
| 40 | ---- |
| 41 | |
| 42 | If you use kmod, you will find it useful to edit /etc/modprobe.conf. |
| 43 | Here is an example of the lines that need to be added: |
| 44 | |
| 45 | alias parport_lowlevel parport_pc |
| 46 | options parport_pc io=0x378,0x278 irq=7,auto |
| 47 | |
| 48 | KMod will then automatically load parport_pc (with the options |
| 49 | "io=0x378,0x278 irq=7,auto") whenever a parallel port device driver |
| 50 | (such as lp) is loaded. |
| 51 | |
| 52 | Note that these are example lines only! You shouldn't in general need |
| 53 | to specify any options to parport_pc in order to be able to use a |
| 54 | parallel port. |
| 55 | |
| 56 | |
| 57 | Parport probe [optional] |
| 58 | ------------- |
| 59 | |
| 60 | In 2.2 kernels there was a module called parport_probe, which was used |
| 61 | for collecting IEEE 1284 device ID information. This has now been |
| 62 | enhanced and now lives with the IEEE 1284 support. When a parallel |
| 63 | port is detected, the devices that are connected to it are analysed, |
| 64 | and information is logged like this: |
| 65 | |
| 66 | parport0: Printer, BJC-210 (Canon) |
| 67 | |
| 68 | The probe information is available from files in /proc/sys/dev/parport/. |
| 69 | |
| 70 | |
| 71 | Parport linked into the kernel statically |
| 72 | ========================================= |
| 73 | |
| 74 | If you compile the parport code into the kernel, then you can use |
| 75 | kernel boot parameters to get the same effect. Add something like the |
| 76 | following to your LILO command line: |
| 77 | |
| 78 | parport=0x3bc parport=0x378,7 parport=0x278,auto,nofifo |
| 79 | |
| 80 | You can have many `parport=...' statements, one for each port you want |
| 81 | to add. Adding `parport=0' to the kernel command-line will disable |
| 82 | parport support entirely. Adding `parport=auto' to the kernel |
| 83 | command-line will make parport use any IRQ lines or DMA channels that |
| 84 | it auto-detects. |
| 85 | |
| 86 | |
| 87 | Files in /proc |
| 88 | ============== |
| 89 | |
| 90 | If you have configured the /proc filesystem into your kernel, you will |
| 91 | see a new directory entry: /proc/sys/dev/parport. In there will be a |
| 92 | directory entry for each parallel port for which parport is |
| 93 | configured. In each of those directories are a collection of files |
| 94 | describing that parallel port. |
| 95 | |
| 96 | The /proc/sys/dev/parport directory tree looks like: |
| 97 | |
| 98 | parport |
| 99 | |-- default |
| 100 | | |-- spintime |
| 101 | | `-- timeslice |
| 102 | |-- parport0 |
| 103 | | |-- autoprobe |
| 104 | | |-- autoprobe0 |
| 105 | | |-- autoprobe1 |
| 106 | | |-- autoprobe2 |
| 107 | | |-- autoprobe3 |
| 108 | | |-- devices |
| 109 | | | |-- active |
| 110 | | | `-- lp |
| 111 | | | `-- timeslice |
| 112 | | |-- base-addr |
| 113 | | |-- irq |
| 114 | | |-- dma |
| 115 | | |-- modes |
| 116 | | `-- spintime |
| 117 | `-- parport1 |
| 118 | |-- autoprobe |
| 119 | |-- autoprobe0 |
| 120 | |-- autoprobe1 |
| 121 | |-- autoprobe2 |
| 122 | |-- autoprobe3 |
| 123 | |-- devices |
| 124 | | |-- active |
| 125 | | `-- ppa |
| 126 | | `-- timeslice |
| 127 | |-- base-addr |
| 128 | |-- irq |
| 129 | |-- dma |
| 130 | |-- modes |
| 131 | `-- spintime |
| 132 | |
| 133 | |
| 134 | File: Contents: |
| 135 | |
| 136 | devices/active A list of the device drivers using that port. A "+" |
| 137 | will appear by the name of the device currently using |
| 138 | the port (it might not appear against any). The |
| 139 | string "none" means that there are no device drivers |
| 140 | using that port. |
| 141 | |
| 142 | base-addr Parallel port's base address, or addresses if the port |
| 143 | has more than one in which case they are separated |
| 144 | with tabs. These values might not have any sensible |
| 145 | meaning for some ports. |
| 146 | |
| 147 | irq Parallel port's IRQ, or -1 if none is being used. |
| 148 | |
| 149 | dma Parallel port's DMA channel, or -1 if none is being |
| 150 | used. |
| 151 | |
| 152 | modes Parallel port's hardware modes, comma-separated, |
| 153 | meaning: |
| 154 | |
| 155 | PCSPP PC-style SPP registers are available. |
| 156 | TRISTATE Port is bidirectional. |
| 157 | COMPAT Hardware acceleration for printers is |
| 158 | available and will be used. |
| 159 | EPP Hardware acceleration for EPP protocol |
| 160 | is available and will be used. |
| 161 | ECP Hardware acceleration for ECP protocol |
| 162 | is available and will be used. |
| 163 | DMA DMA is available and will be used. |
| 164 | |
| 165 | Note that the current implementation will only take |
| 166 | advantage of COMPAT and ECP modes if it has an IRQ |
| 167 | line to use. |
| 168 | |
| 169 | autoprobe Any IEEE-1284 device ID information that has been |
| 170 | acquired from the (non-IEEE 1284.3) device. |
| 171 | |
| 172 | autoprobe[0-3] IEEE 1284 device ID information retrieved from |
| 173 | daisy-chain devices that conform to IEEE 1284.3. |
| 174 | |
| 175 | spintime The number of microseconds to busy-loop while waiting |
| 176 | for the peripheral to respond. You might find that |
| 177 | adjusting this improves performance, depending on your |
| 178 | peripherals. This is a port-wide setting, i.e. it |
| 179 | applies to all devices on a particular port. |
| 180 | |
| 181 | timeslice The number of milliseconds that a device driver is |
| 182 | allowed to keep a port claimed for. This is advisory, |
| 183 | and driver can ignore it if it must. |
| 184 | |
| 185 | default/* The defaults for spintime and timeslice. When a new |
| 186 | port is registered, it picks up the default spintime. |
| 187 | When a new device is registered, it picks up the |
| 188 | default timeslice. |
| 189 | |
| 190 | Device drivers |
| 191 | ============== |
| 192 | |
| 193 | Once the parport code is initialised, you can attach device drivers to |
| 194 | specific ports. Normally this happens automatically; if the lp driver |
| 195 | is loaded it will create one lp device for each port found. You can |
| 196 | override this, though, by using parameters either when you load the lp |
| 197 | driver: |
| 198 | |
| 199 | # insmod lp parport=0,2 |
| 200 | |
| 201 | or on the LILO command line: |
| 202 | |
| 203 | lp=parport0 lp=parport2 |
| 204 | |
| 205 | Both the above examples would inform lp that you want /dev/lp0 to be |
| 206 | the first parallel port, and /dev/lp1 to be the _third_ parallel port, |
| 207 | with no lp device associated with the second port (parport1). Note |
| 208 | that this is different to the way older kernels worked; there used to |
| 209 | be a static association between the I/O port address and the device |
| 210 | name, so /dev/lp0 was always the port at 0x3bc. This is no longer the |
| 211 | case - if you only have one port, it will default to being /dev/lp0, |
| 212 | regardless of base address. |
| 213 | |
| 214 | Also: |
| 215 | |
| 216 | * If you selected the IEEE 1284 support at compile time, you can say |
| 217 | `lp=auto' on the kernel command line, and lp will create devices |
| 218 | only for those ports that seem to have printers attached. |
| 219 | |
| 220 | * If you give PLIP the `timid' parameter, either with `plip=timid' on |
| 221 | the command line, or with `insmod plip timid=1' when using modules, |
| 222 | it will avoid any ports that seem to be in use by other devices. |
| 223 | |
| 224 | * IRQ autoprobing works only for a few port types at the moment. |
| 225 | |
| 226 | Reporting printer problems with parport |
| 227 | ======================================= |
| 228 | |
| 229 | If you are having problems printing, please go through these steps to |
| 230 | try to narrow down where the problem area is. |
| 231 | |
| 232 | When reporting problems with parport, really you need to give all of |
| 233 | the messages that parport_pc spits out when it initialises. There are |
| 234 | several code paths: |
| 235 | |
| 236 | o polling |
| 237 | o interrupt-driven, protocol in software |
| 238 | o interrupt-driven, protocol in hardware using PIO |
| 239 | o interrupt-driven, protocol in hardware using DMA |
| 240 | |
| 241 | The kernel messages that parport_pc logs give an indication of which |
| 242 | code path is being used. (They could be a lot better actually..) |
| 243 | |
| 244 | For normal printer protocol, having IEEE 1284 modes enabled or not |
| 245 | should not make a difference. |
| 246 | |
| 247 | To turn off the 'protocol in hardware' code paths, disable |
| 248 | CONFIG_PARPORT_PC_FIFO. Note that when they are enabled they are not |
| 249 | necessarily _used_; it depends on whether the hardware is available, |
| 250 | enabled by the BIOS, and detected by the driver. |
| 251 | |
| 252 | So, to start with, disable CONFIG_PARPORT_PC_FIFO, and load parport_pc |
| 253 | with 'irq=none'. See if printing works then. It really should, |
| 254 | because this is the simplest code path. |
| 255 | |
| 256 | If that works fine, try with 'io=0x378 irq=7' (adjust for your |
| 257 | hardware), to make it use interrupt-driven in-software protocol. |
| 258 | |
| 259 | If _that_ works fine, then one of the hardware modes isn't working |
| 260 | right. Enable CONFIG_PARPORT_PC_FIFO (no, it isn't a module option, |
| 261 | and yes, it should be), set the port to ECP mode in the BIOS and note |
| 262 | the DMA channel, and try with: |
| 263 | |
| 264 | io=0x378 irq=7 dma=none (for PIO) |
| 265 | io=0x378 irq=7 dma=3 (for DMA) |
| 266 | -- |
| 267 | philb@gnu.org |
| 268 | tim@cyberelk.net |