PARPORT interface documentation
  -------------------------------
  
  Time-stamp: <2000-02-24 13:30:20 twaugh>
  
  Described here are the following functions:
  
  Global functions:
    parport_register_driver
    parport_unregister_driver
    parport_enumerate
    parport_register_device
    parport_unregister_device
    parport_claim
    parport_claim_or_block
    parport_release
    parport_yield
    parport_yield_blocking
    parport_wait_peripheral
    parport_poll_peripheral
    parport_wait_event
    parport_negotiate
    parport_read
    parport_write
    parport_open
    parport_close
    parport_device_id
    parport_device_coords
    parport_find_class
    parport_find_device
    parport_set_timeout
  
  Port functions (can be overridden by low-level drivers):
    SPP:
      port->ops->read_data
      port->ops->write_data
      port->ops->read_status
      port->ops->read_control
      port->ops->write_control
      port->ops->frob_control
      port->ops->enable_irq
      port->ops->disable_irq
      port->ops->data_forward
      port->ops->data_reverse
  
    EPP:
      port->ops->epp_write_data
      port->ops->epp_read_data
      port->ops->epp_write_addr
      port->ops->epp_read_addr
  
    ECP:
      port->ops->ecp_write_data
      port->ops->ecp_read_data
      port->ops->ecp_write_addr
  
    Other:
      port->ops->nibble_read_data
      port->ops->byte_read_data
      port->ops->compat_write_data
  
  The parport subsystem comprises 'parport' (the core port-sharing
  code), and a variety of low-level drivers that actually do the port
  accesses.  Each low-level driver handles a particular style of port
  (PC, Amiga, and so on).
  
  The parport interface to the device driver author can be broken down
  into global functions and port functions.
  
  The global functions are mostly for communicating between the device
  driver and the parport subsystem: acquiring a list of available ports,
  claiming a port for exclusive use, and so on.  They also include
  'generic' functions for doing standard things that will work on any
  IEEE 1284-capable architecture.
  
  The port functions are provided by the low-level drivers, although the
  core parport module provides generic 'defaults' for some routines.
  The port functions can be split into three groups: SPP, EPP, and ECP.
  
  SPP (Standard Parallel Port) functions modify so-called 'SPP'
  registers: data, status, and control.  The hardware may not actually
  have registers exactly like that, but the PC does and this interface is
  modelled after common PC implementations.  Other low-level drivers may
  be able to emulate most of the functionality.
  
  EPP (Enhanced Parallel Port) functions are provided for reading and
  writing in IEEE 1284 EPP mode, and ECP (Extended Capabilities Port)
  functions are used for IEEE 1284 ECP mode. (What about BECP? Does
  anyone care?)
  
  Hardware assistance for EPP and/or ECP transfers may or may not be
  available, and if it is available it may or may not be used.  If
  hardware is not used, the transfer will be software-driven.  In order
  to cope with peripherals that only tenuously support IEEE 1284, a
  low-level driver specific function is provided, for altering 'fudge
  factors'.
  
  GLOBAL FUNCTIONS
  ----------------
  
  parport_register_driver - register a device driver with parport
  -----------------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  struct parport_driver {
  	const char *name;
  	void (*attach) (struct parport *);
  	void (*detach) (struct parport *);
  	struct parport_driver *next;
  };
  int parport_register_driver (struct parport_driver *driver);
  
  DESCRIPTION
  
  In order to be notified about parallel ports when they are detected,
  parport_register_driver should be called.  Your driver will
  immediately be notified of all ports that have already been detected,
  and of each new port as low-level drivers are loaded.
  
  A 'struct parport_driver' contains the textual name of your driver,
  a pointer to a function to handle new ports, and a pointer to a
  function to handle ports going away due to a low-level driver
  unloading.  Ports will only be detached if they are not being used
  (i.e. there are no devices registered on them).
  
  The visible parts of the 'struct parport *' argument given to
  attach/detach are:
  
  struct parport
  {
  	struct parport *next; /* next parport in list */
  	const char *name;     /* port's name */
  	unsigned int modes;   /* bitfield of hardware modes */
  	struct parport_device_info probe_info;
  			      /* IEEE1284 info */
  	int number;           /* parport index */
  	struct parport_operations *ops;
  	...
  };
  
  There are other members of the structure, but they should not be
  touched.
  
  The 'modes' member summarises the capabilities of the underlying
  hardware.  It consists of flags which may be bitwise-ored together:
  
    PARPORT_MODE_PCSPP		IBM PC registers are available,
  				i.e. functions that act on data,
  				control and status registers are
  				probably writing directly to the
  				hardware.
    PARPORT_MODE_TRISTATE		The data drivers may be turned off.
  				This allows the data lines to be used
  				for reverse (peripheral to host)
  				transfers.
    PARPORT_MODE_COMPAT		The hardware can assist with
  				compatibility-mode (printer)
  				transfers, i.e. compat_write_block.
    PARPORT_MODE_EPP		The hardware can assist with EPP
  				transfers.
    PARPORT_MODE_ECP		The hardware can assist with ECP
  				transfers.
    PARPORT_MODE_DMA		The hardware can use DMA, so you might
  				want to pass ISA DMA-able memory
  				(i.e. memory allocated using the
  				GFP_DMA flag with kmalloc) to the
  				low-level driver in order to take
  				advantage of it.
  
  There may be other flags in 'modes' as well.
  
  The contents of 'modes' is advisory only.  For example, if the
  hardware is capable of DMA, and PARPORT_MODE_DMA is in 'modes', it
  doesn't necessarily mean that DMA will always be used when possible.
  Similarly, hardware that is capable of assisting ECP transfers won't
  necessarily be used.
  
  RETURN VALUE
  
  Zero on success, otherwise an error code.
  
  ERRORS
  
  None. (Can it fail? Why return int?)
  
  EXAMPLE
  
  static void lp_attach (struct parport *port)
  {
  	...
  	private = kmalloc (...);
  	dev[count++] = parport_register_device (...);
  	...
  }
  
  static void lp_detach (struct parport *port)
  {
  	...
  }
  
  static struct parport_driver lp_driver = {
  	"lp",
  	lp_attach,
  	lp_detach,
  	NULL /* always put NULL here */
  };
  
  int lp_init (void)
  {
  	...
  	if (parport_register_driver (&lp_driver)) {
  		/* Failed; nothing we can do. */
  		return -EIO;
  	}
  	...
  }
  
  SEE ALSO
  
  parport_unregister_driver, parport_register_device, parport_enumerate
  
  parport_unregister_driver - tell parport to forget about this driver
  -------------------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  struct parport_driver {
  	const char *name;
  	void (*attach) (struct parport *);
  	void (*detach) (struct parport *);
  	struct parport_driver *next;
  };
  void parport_unregister_driver (struct parport_driver *driver);
  
  DESCRIPTION
  
  This tells parport not to notify the device driver of new ports or of
  ports going away.  Registered devices belonging to that driver are NOT
  unregistered: parport_unregister_device must be used for each one.
  
  EXAMPLE
  
  void cleanup_module (void)
  {
  	...
  	/* Stop notifications. */
  	parport_unregister_driver (&lp_driver);
  
  	/* Unregister devices. */
  	for (i = 0; i < NUM_DEVS; i++)
  		parport_unregister_device (dev[i]);
  	...
  }
  
  SEE ALSO
  
  parport_register_driver, parport_enumerate
  
  parport_enumerate - retrieve a list of parallel ports (DEPRECATED)
  -----------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  struct parport *parport_enumerate (void);
  
  DESCRIPTION
  
  Retrieve the first of a list of valid parallel ports for this machine.
  Successive parallel ports can be found using the 'struct parport
  *next' element of the 'struct parport *' that is returned.  If 'next'
  is NULL, there are no more parallel ports in the list.  The number of
  ports in the list will not exceed PARPORT_MAX.
  
  RETURN VALUE
  
  A 'struct parport *' describing a valid parallel port for the machine,
  or NULL if there are none.
  
  ERRORS
  
  This function can return NULL to indicate that there are no parallel
  ports to use.
  
  EXAMPLE
  
  int detect_device (void)
  {
  	struct parport *port;
  
  	for (port = parport_enumerate ();
  	     port != NULL;
  	     port = port->next) {
  		/* Try to detect a device on the port... */
  		...
               }
  	}
  
  	...
  }
  
  NOTES
  
  parport_enumerate is deprecated; parport_register_driver should be
  used instead.
  
  SEE ALSO
  
  parport_register_driver, parport_unregister_driver
  
  parport_register_device - register to use a port
  -----------------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  typedef int (*preempt_func) (void *handle);
  typedef void (*wakeup_func) (void *handle);
  typedef int (*irq_func) (int irq, void *handle, struct pt_regs *);
  
  struct pardevice *parport_register_device(struct parport *port,
                                            const char *name,
                                            preempt_func preempt,
                                            wakeup_func wakeup,
                                            irq_func irq,
                                            int flags,
                                            void *handle);
  
  DESCRIPTION
  
  Use this function to register your device driver on a parallel port
  ('port').  Once you have done that, you will be able to use
  parport_claim and parport_release in order to use the port.
  
  The ('name') argument is the name of the device that appears in /proc
  filesystem. The string must be valid for the whole lifetime of the
  device (until parport_unregister_device is called).
  
  This function will register three callbacks into your driver:
  'preempt', 'wakeup' and 'irq'.  Each of these may be NULL in order to
  indicate that you do not want a callback.
  
  When the 'preempt' function is called, it is because another driver
  wishes to use the parallel port.  The 'preempt' function should return
  non-zero if the parallel port cannot be released yet -- if zero is
  returned, the port is lost to another driver and the port must be
  re-claimed before use.
  
  The 'wakeup' function is called once another driver has released the
  port and no other driver has yet claimed it.  You can claim the
  parallel port from within the 'wakeup' function (in which case the
  claim is guaranteed to succeed), or choose not to if you don't need it
  now.
  
  If an interrupt occurs on the parallel port your driver has claimed,
  the 'irq' function will be called. (Write something about shared
  interrupts here.)
  
  The 'handle' is a pointer to driver-specific data, and is passed to
  the callback functions.
  
  'flags' may be a bitwise combination of the following flags:
  
          Flag            Meaning
    PARPORT_DEV_EXCL	The device cannot share the parallel port at all.
  			Use this only when absolutely necessary.
  
  The typedefs are not actually defined -- they are only shown in order
  to make the function prototype more readable.
  
  The visible parts of the returned 'struct pardevice' are:
  
  struct pardevice {
  	struct parport *port;	/* Associated port */
  	void *private;		/* Device driver's 'handle' */
  	...
  };
  
  RETURN VALUE
  
  A 'struct pardevice *': a handle to the registered parallel port
  device that can be used for parport_claim, parport_release, etc.
  
  ERRORS
  
  A return value of NULL indicates that there was a problem registering
  a device on that port.
  
  EXAMPLE
  
  static int preempt (void *handle)
  {
  	if (busy_right_now)
  		return 1;
  
  	must_reclaim_port = 1;
  	return 0;
  }
  
  static void wakeup (void *handle)
  {
  	struct toaster *private = handle;
  	struct pardevice *dev = private->dev;
  	if (!dev) return; /* avoid races */
  
  	if (want_port)
  		parport_claim (dev);
  }
  
  static int toaster_detect (struct toaster *private, struct parport *port)
  {
  	private->dev = parport_register_device (port, "toaster", preempt,
  					        wakeup, NULL, 0,
  						private);
  	if (!private->dev)
  		/* Couldn't register with parport. */
  		return -EIO;
  
  	must_reclaim_port = 0;
  	busy_right_now = 1;
  	parport_claim_or_block (private->dev);
  	...
  	/* Don't need the port while the toaster warms up. */
  	busy_right_now = 0;
  	...
  	busy_right_now = 1;
  	if (must_reclaim_port) {
  		parport_claim_or_block (private->dev);
  		must_reclaim_port = 0;
  	}
  	...
  }
  
  SEE ALSO
  
  parport_unregister_device, parport_claim
  
  parport_unregister_device - finish using a port
  -------------------------
  
  SYNPOPSIS
  
  #include <linux/parport.h>
  
  void parport_unregister_device (struct pardevice *dev);
  
  DESCRIPTION
  
  This function is the opposite of parport_register_device.  After using
  parport_unregister_device, 'dev' is no longer a valid device handle.
  
  You should not unregister a device that is currently claimed, although
  if you do it will be released automatically.
  
  EXAMPLE
  
  	...
  	kfree (dev->private); /* before we lose the pointer */
  	parport_unregister_device (dev);
  	...
  
  SEE ALSO
  
  parport_unregister_driver
  
  parport_claim, parport_claim_or_block - claim the parallel port for a device
  -------------------------------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  int parport_claim (struct pardevice *dev);
  int parport_claim_or_block (struct pardevice *dev);
  
  DESCRIPTION
  
  These functions attempt to gain control of the parallel port on which
  'dev' is registered.  'parport_claim' does not block, but
  'parport_claim_or_block' may do. (Put something here about blocking
  interruptibly or non-interruptibly.)
  
  You should not try to claim a port that you have already claimed.
  
  RETURN VALUE
  
  A return value of zero indicates that the port was successfully
  claimed, and the caller now has possession of the parallel port.
  
  If 'parport_claim_or_block' blocks before returning successfully, the
  return value is positive.
  
  ERRORS
  
    -EAGAIN  The port is unavailable at the moment, but another attempt
             to claim it may succeed.
  
  SEE ALSO
  
  parport_release
  
  parport_release - release the parallel port
  ---------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  void parport_release (struct pardevice *dev);
  
  DESCRIPTION
  
  Once a parallel port device has been claimed, it can be released using
  'parport_release'.  It cannot fail, but you should not release a
  device that you do not have possession of.
  
  EXAMPLE
  
  static size_t write (struct pardevice *dev, const void *buf,
  		     size_t len)
  {
  	...
  	written = dev->port->ops->write_ecp_data (dev->port, buf,
  						  len);
  	parport_release (dev);
  	...
  }
  
  
  SEE ALSO
  
  change_mode, parport_claim, parport_claim_or_block, parport_yield
  
  parport_yield, parport_yield_blocking - temporarily release a parallel port
  -------------------------------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  int parport_yield (struct pardevice *dev)
  int parport_yield_blocking (struct pardevice *dev);
  
  DESCRIPTION
  
  When a driver has control of a parallel port, it may allow another
  driver to temporarily 'borrow' it.  'parport_yield' does not block;
  'parport_yield_blocking' may do.
  
  RETURN VALUE
  
  A return value of zero indicates that the caller still owns the port
  and the call did not block.
  
  A positive return value from 'parport_yield_blocking' indicates that
  the caller still owns the port and the call blocked.
  
  A return value of -EAGAIN indicates that the caller no longer owns the
  port, and it must be re-claimed before use.
  
  ERRORS
  
    -EAGAIN  Ownership of the parallel port was given away.
  
  SEE ALSO
  
  parport_release
  
  parport_wait_peripheral - wait for status lines, up to 35ms
  -----------------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  int parport_wait_peripheral (struct parport *port,
  			     unsigned char mask,
  			     unsigned char val);
  
  DESCRIPTION
  
  Wait for the status lines in mask to match the values in val.
  
  RETURN VALUE
  
   -EINTR  a signal is pending
        0  the status lines in mask have values in val
        1  timed out while waiting (35ms elapsed)
  
  SEE ALSO
  
  parport_poll_peripheral
  
  parport_poll_peripheral - wait for status lines, in usec
  -----------------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  int parport_poll_peripheral (struct parport *port,
  			     unsigned char mask,
  			     unsigned char val,
  			     int usec);
  
  DESCRIPTION
  
  Wait for the status lines in mask to match the values in val.
  
  RETURN VALUE
  
   -EINTR  a signal is pending
        0  the status lines in mask have values in val
        1  timed out while waiting (usec microseconds have elapsed)
  
  SEE ALSO
  
  parport_wait_peripheral
  
  parport_wait_event - wait for an event on a port
  ------------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  int parport_wait_event (struct parport *port, signed long timeout)
  
  DESCRIPTION
  
  Wait for an event (e.g. interrupt) on a port.  The timeout is in
  jiffies.
  
  RETURN VALUE
  
        0  success
       <0  error (exit as soon as possible)
       >0  timed out
  
  parport_negotiate - perform IEEE 1284 negotiation
  -----------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  int parport_negotiate (struct parport *, int mode);
  
  DESCRIPTION
  
  Perform IEEE 1284 negotiation.
  
  RETURN VALUE
  
       0  handshake OK; IEEE 1284 peripheral and mode available
      -1  handshake failed; peripheral not compliant (or none present)
       1  handshake OK; IEEE 1284 peripheral present but mode not
          available
  
  SEE ALSO
  
  parport_read, parport_write
  
  parport_read - read data from device
  ------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  ssize_t parport_read (struct parport *, void *buf, size_t len);
  
  DESCRIPTION
  
  Read data from device in current IEEE 1284 transfer mode.  This only
  works for modes that support reverse data transfer.
  
  RETURN VALUE
  
  If negative, an error code; otherwise the number of bytes transferred.
  
  SEE ALSO
  
  parport_write, parport_negotiate
  
  parport_write - write data to device
  -------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  ssize_t parport_write (struct parport *, const void *buf, size_t len);
  
  DESCRIPTION
  
  Write data to device in current IEEE 1284 transfer mode.  This only
  works for modes that support forward data transfer.
  
  RETURN VALUE
  
  If negative, an error code; otherwise the number of bytes transferred.
  
  SEE ALSO
  
  parport_read, parport_negotiate
  
  parport_open - register device for particular device number
  ------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  struct pardevice *parport_open (int devnum, const char *name,
  			        int (*pf) (void *),
  				void (*kf) (void *),
  				void (*irqf) (int, void *,
  					      struct pt_regs *),
  				int flags, void *handle);
  
  DESCRIPTION
  
  This is like parport_register_device but takes a device number instead
  of a pointer to a struct parport.
  
  RETURN VALUE
  
  See parport_register_device.  If no device is associated with devnum,
  NULL is returned.
  
  SEE ALSO
  
  parport_register_device
  
  parport_close - unregister device for particular device number
  -------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  void parport_close (struct pardevice *dev);
  
  DESCRIPTION
  
  This is the equivalent of parport_unregister_device for parport_open.
  
  SEE ALSO
  
  parport_unregister_device, parport_open
  
  parport_device_id - obtain IEEE 1284 Device ID
  -----------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  ssize_t parport_device_id (int devnum, char *buffer, size_t len);
  
  DESCRIPTION
  
  Obtains the IEEE 1284 Device ID associated with a given device.
  
  RETURN VALUE
  
  If negative, an error code; otherwise, the number of bytes of buffer
  that contain the device ID.  The format of the device ID is as
  follows:
  
  [length][ID]
  
  The first two bytes indicate the inclusive length of the entire Device
  ID, and are in big-endian order.  The ID is a sequence of pairs of the
  form:
  
  key:value;
  
  NOTES
  
  Many devices have ill-formed IEEE 1284 Device IDs.
  
  SEE ALSO
  
  parport_find_class, parport_find_device
  
  parport_device_coords - convert device number to device coordinates
  ------------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  int parport_device_coords (int devnum, int *parport, int *mux,
  			   int *daisy);
  
  DESCRIPTION
  
  Convert between device number (zero-based) and device coordinates
  (port, multiplexor, daisy chain address).
  
  RETURN VALUE
  
  Zero on success, in which case the coordinates are (*parport, *mux,
  *daisy).
  
  SEE ALSO
  
  parport_open, parport_device_id
  
  parport_find_class - find a device by its class
  ------------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  typedef enum {
  	PARPORT_CLASS_LEGACY = 0,       /* Non-IEEE1284 device */
  	PARPORT_CLASS_PRINTER,
  	PARPORT_CLASS_MODEM,
  	PARPORT_CLASS_NET,
  	PARPORT_CLASS_HDC,              /* Hard disk controller */
  	PARPORT_CLASS_PCMCIA,
  	PARPORT_CLASS_MEDIA,            /* Multimedia device */
  	PARPORT_CLASS_FDC,              /* Floppy disk controller */
  	PARPORT_CLASS_PORTS,
  	PARPORT_CLASS_SCANNER,
  	PARPORT_CLASS_DIGCAM,
  	PARPORT_CLASS_OTHER,            /* Anything else */
  	PARPORT_CLASS_UNSPEC,           /* No CLS field in ID */
  	PARPORT_CLASS_SCSIADAPTER
  } parport_device_class;
  
  int parport_find_class (parport_device_class cls, int from);
  
  DESCRIPTION
  
  Find a device by class.  The search starts from device number from+1.
  
  RETURN VALUE
  
  The device number of the next device in that class, or -1 if no such
  device exists.
  
  NOTES
  
  Example usage:
  
  int devnum = -1;
  while ((devnum = parport_find_class (PARPORT_CLASS_DIGCAM, devnum)) != -1) {
      struct pardevice *dev = parport_open (devnum, ...);
      ...
  }
  
  SEE ALSO
  
  parport_find_device, parport_open, parport_device_id
  
  parport_find_device - find a device by its class
  ------------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  int parport_find_device (const char *mfg, const char *mdl, int from);
  
  DESCRIPTION
  
  Find a device by vendor and model.  The search starts from device
  number from+1.
  
  RETURN VALUE
  
  The device number of the next device matching the specifications, or
  -1 if no such device exists.
  
  NOTES
  
  Example usage:
  
  int devnum = -1;
  while ((devnum = parport_find_device ("IOMEGA", "ZIP+", devnum)) != -1) {
      struct pardevice *dev = parport_open (devnum, ...);
      ...
  }
  
  SEE ALSO
  
  parport_find_class, parport_open, parport_device_id
  
  parport_set_timeout - set the inactivity timeout
  -------------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  long parport_set_timeout (struct pardevice *dev, long inactivity);
  
  DESCRIPTION
  
  Set the inactivity timeout, in jiffies, for a registered device.  The
  previous timeout is returned.
  
  RETURN VALUE
  
  The previous timeout, in jiffies.
  
  NOTES
  
  Some of the port->ops functions for a parport may take time, owing to
  delays at the peripheral.  After the peripheral has not responded for
  'inactivity' jiffies, a timeout will occur and the blocking function
  will return.
  
  A timeout of 0 jiffies is a special case: the function must do as much
  as it can without blocking or leaving the hardware in an unknown
  state.  If port operations are performed from within an interrupt
  handler, for instance, a timeout of 0 jiffies should be used.
  
  Once set for a registered device, the timeout will remain at the set
  value until set again.
  
  SEE ALSO
  
  port->ops->xxx_read/write_yyy
  
  PORT FUNCTIONS
  --------------
  
  The functions in the port->ops structure (struct parport_operations)
  are provided by the low-level driver responsible for that port.
  
  port->ops->read_data - read the data register
  --------------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  struct parport_operations {
  	...
  	unsigned char (*read_data) (struct parport *port);
  	...
  };
  
  DESCRIPTION
  
  If port->modes contains the PARPORT_MODE_TRISTATE flag and the
  PARPORT_CONTROL_DIRECTION bit in the control register is set, this
  returns the value on the data pins.  If port->modes contains the
  PARPORT_MODE_TRISTATE flag and the PARPORT_CONTROL_DIRECTION bit is
  not set, the return value _may_ be the last value written to the data
  register.  Otherwise the return value is undefined.
  
  SEE ALSO
  
  write_data, read_status, write_control
  
  port->ops->write_data - write the data register
  ---------------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  struct parport_operations {
  	...
  	void (*write_data) (struct parport *port, unsigned char d);
  	...
  };
  
  DESCRIPTION
  
  Writes to the data register.  May have side-effects (a STROBE pulse,
  for instance).
  
  SEE ALSO
  
  read_data, read_status, write_control
  
  port->ops->read_status - read the status register
  ----------------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  struct parport_operations {
  	...
  	unsigned char (*read_status) (struct parport *port);
  	...
  };
  
  DESCRIPTION
  
  Reads from the status register.  This is a bitmask:
  
  - PARPORT_STATUS_ERROR (printer fault, "nFault")
  - PARPORT_STATUS_SELECT (on-line, "Select")
  - PARPORT_STATUS_PAPEROUT (no paper, "PError")
  - PARPORT_STATUS_ACK (handshake, "nAck")
  - PARPORT_STATUS_BUSY (busy, "Busy")
  
  There may be other bits set.
  
  SEE ALSO
  
  read_data, write_data, write_control
  
  port->ops->read_control - read the control register
  -----------------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  struct parport_operations {
  	...
  	unsigned char (*read_control) (struct parport *port);
  	...
  };
  
  DESCRIPTION
  
  Returns the last value written to the control register (either from
  write_control or frob_control).  No port access is performed.
  
  SEE ALSO
  
  read_data, write_data, read_status, write_control
  
  port->ops->write_control - write the control register
  ------------------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  struct parport_operations {
  	...
  	void (*write_control) (struct parport *port, unsigned char s);
  	...
  };
  
  DESCRIPTION
  
  Writes to the control register. This is a bitmask:
                            _______
  - PARPORT_CONTROL_STROBE (nStrobe)
                            _______
  - PARPORT_CONTROL_AUTOFD (nAutoFd)
                          _____
  - PARPORT_CONTROL_INIT (nInit)
                            _________
  - PARPORT_CONTROL_SELECT (nSelectIn)
  
  SEE ALSO
  
  read_data, write_data, read_status, frob_control
  
  port->ops->frob_control - write control register bits
  -----------------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  struct parport_operations {
  	...
  	unsigned char (*frob_control) (struct parport *port,
  				       unsigned char mask,
  				       unsigned char val);
  	...
  };
  
  DESCRIPTION
  
  This is equivalent to reading from the control register, masking out
  the bits in mask, exclusive-or'ing with the bits in val, and writing
  the result to the control register.
  
  As some ports don't allow reads from the control port, a software copy
  of its contents is maintained, so frob_control is in fact only one
  port access.
  
  SEE ALSO
  
  read_data, write_data, read_status, write_control
  
  port->ops->enable_irq - enable interrupt generation
  ---------------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  struct parport_operations {
  	...
  	void (*enable_irq) (struct parport *port);
  	...
  };
  
  DESCRIPTION
  
  The parallel port hardware is instructed to generate interrupts at
  appropriate moments, although those moments are
  architecture-specific.  For the PC architecture, interrupts are
  commonly generated on the rising edge of nAck.
  
  SEE ALSO
  
  disable_irq
  
  port->ops->disable_irq - disable interrupt generation
  ----------------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  struct parport_operations {
  	...
  	void (*disable_irq) (struct parport *port);
  	...
  };
  
  DESCRIPTION
  
  The parallel port hardware is instructed not to generate interrupts.
  The interrupt itself is not masked.
  
  SEE ALSO
  
  enable_irq
  
  port->ops->data_forward - enable data drivers
  -----------------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  struct parport_operations {
  	...
  	void (*data_forward) (struct parport *port);
  	...
  };
  
  DESCRIPTION
  
  Enables the data line drivers, for 8-bit host-to-peripheral
  communications.
  
  SEE ALSO
  
  data_reverse
  
  port->ops->data_reverse - tristate the buffer
  -----------------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  struct parport_operations {
  	...
  	void (*data_reverse) (struct parport *port);
  	...
  };
  
  DESCRIPTION
  
  Places the data bus in a high impedance state, if port->modes has the
  PARPORT_MODE_TRISTATE bit set.
  
  SEE ALSO
  
  data_forward
  
  port->ops->epp_write_data - write EPP data
  -------------------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  struct parport_operations {
  	...
  	size_t (*epp_write_data) (struct parport *port, const void *buf,
  				  size_t len, int flags);
  	...
  };
  
  DESCRIPTION
  
  Writes data in EPP mode, and returns the number of bytes written.
  
  The 'flags' parameter may be one or more of the following,
  bitwise-or'ed together:
  
  PARPORT_EPP_FAST	Use fast transfers. Some chips provide 16-bit and
  			32-bit registers.  However, if a transfer
  			times out, the return value may be unreliable.
  
  SEE ALSO
  
  epp_read_data, epp_write_addr, epp_read_addr
  
  port->ops->epp_read_data - read EPP data
  ------------------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  struct parport_operations {
  	...
  	size_t (*epp_read_data) (struct parport *port, void *buf,
  				 size_t len, int flags);
  	...
  };
  
  DESCRIPTION
  
  Reads data in EPP mode, and returns the number of bytes read.
  
  The 'flags' parameter may be one or more of the following,
  bitwise-or'ed together:
  
  PARPORT_EPP_FAST	Use fast transfers. Some chips provide 16-bit and
  			32-bit registers.  However, if a transfer
  			times out, the return value may be unreliable.
  
  SEE ALSO
  
  epp_write_data, epp_write_addr, epp_read_addr
  
  port->ops->epp_write_addr - write EPP address
  -------------------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  struct parport_operations {
  	...
  	size_t (*epp_write_addr) (struct parport *port,
  				  const void *buf, size_t len, int flags);
  	...
  };
  
  DESCRIPTION
  
  Writes EPP addresses (8 bits each), and returns the number written.
  
  The 'flags' parameter may be one or more of the following,
  bitwise-or'ed together:
  
  PARPORT_EPP_FAST	Use fast transfers. Some chips provide 16-bit and
  			32-bit registers.  However, if a transfer
  			times out, the return value may be unreliable.
  
  (Does PARPORT_EPP_FAST make sense for this function?)
  
  SEE ALSO
  
  epp_write_data, epp_read_data, epp_read_addr
  
  port->ops->epp_read_addr - read EPP address
  ------------------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  struct parport_operations {
  	...
  	size_t (*epp_read_addr) (struct parport *port, void *buf,
  				 size_t len, int flags);
  	...
  };
  
  DESCRIPTION
  
  Reads EPP addresses (8 bits each), and returns the number read.
  
  The 'flags' parameter may be one or more of the following,
  bitwise-or'ed together:
  
  PARPORT_EPP_FAST	Use fast transfers. Some chips provide 16-bit and
  			32-bit registers.  However, if a transfer
  			times out, the return value may be unreliable.
  
  (Does PARPORT_EPP_FAST make sense for this function?)
  
  SEE ALSO
  
  epp_write_data, epp_read_data, epp_write_addr
  
  port->ops->ecp_write_data - write a block of ECP data
  -------------------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  struct parport_operations {
  	...
  	size_t (*ecp_write_data) (struct parport *port,
  				  const void *buf, size_t len, int flags);
  	...
  };
  
  DESCRIPTION
  
  Writes a block of ECP data.  The 'flags' parameter is ignored.
  
  RETURN VALUE
  
  The number of bytes written.
  
  SEE ALSO
  
  ecp_read_data, ecp_write_addr
  
  port->ops->ecp_read_data - read a block of ECP data
  ------------------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  struct parport_operations {
  	...
  	size_t (*ecp_read_data) (struct parport *port,
  				 void *buf, size_t len, int flags);
  	...
  };
  
  DESCRIPTION
  
  Reads a block of ECP data.  The 'flags' parameter is ignored.
  
  RETURN VALUE
  
  The number of bytes read.  NB. There may be more unread data in a
  FIFO.  Is there a way of stunning the FIFO to prevent this?
  
  SEE ALSO
  
  ecp_write_block, ecp_write_addr
  
  port->ops->ecp_write_addr - write a block of ECP addresses
  -------------------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  struct parport_operations {
  	...
  	size_t (*ecp_write_addr) (struct parport *port,
  				  const void *buf, size_t len, int flags);
  	...
  };
  
  DESCRIPTION
  
  Writes a block of ECP addresses.  The 'flags' parameter is ignored.
  
  RETURN VALUE
  
  The number of bytes written.
  
  NOTES
  
  This may use a FIFO, and if so shall not return until the FIFO is empty.
  
  SEE ALSO
  
  ecp_read_data, ecp_write_data
  
  port->ops->nibble_read_data - read a block of data in nibble mode
  ---------------------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  struct parport_operations {
  	...
  	size_t (*nibble_read_data) (struct parport *port,
  				    void *buf, size_t len, int flags);
  	...
  };
  
  DESCRIPTION
  
  Reads a block of data in nibble mode.  The 'flags' parameter is ignored.
  
  RETURN VALUE
  
  The number of whole bytes read.
  
  SEE ALSO
  
  byte_read_data, compat_write_data
  
  port->ops->byte_read_data - read a block of data in byte mode
  -------------------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  struct parport_operations {
  	...
  	size_t (*byte_read_data) (struct parport *port,
  				  void *buf, size_t len, int flags);
  	...
  };
  
  DESCRIPTION
  
  Reads a block of data in byte mode.  The 'flags' parameter is ignored.
  
  RETURN VALUE
  
  The number of bytes read.
  
  SEE ALSO
  
  nibble_read_data, compat_write_data
  
  port->ops->compat_write_data - write a block of data in compatibility mode
  ----------------------------
  
  SYNOPSIS
  
  #include <linux/parport.h>
  
  struct parport_operations {
  	...
  	size_t (*compat_write_data) (struct parport *port,
  				     const void *buf, size_t len, int flags);
  	...
  };
  
  DESCRIPTION
  
  Writes a block of data in compatibility mode.  The 'flags' parameter
  is ignored.
  
  RETURN VALUE
  
  The number of bytes written.
  
  SEE ALSO
  
  nibble_read_data, byte_read_data