cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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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