parport.rst 9.3 KB

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