text: /*
   * comedidev.h
   * header file for kernel-only structures, variables, and constants
   *
   * COMEDI - Linux Control and Measurement Device Interface
   * Copyright (C) 1997-2000 David A. Schleef <ds@schleef.org>
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   */
  
  #ifndef _COMEDIDEV_H
  #define _COMEDIDEV_H
  
  #include <linux/dma-mapping.h>
  #include <linux/mutex.h>
  #include <linux/spinlock_types.h>
  #include <linux/rwsem.h>
  #include <linux/kref.h>
  
  #include "comedi.h"
  
  #define COMEDI_VERSION(a, b, c) (((a) << 16) + ((b) << 8) + (c))
  #define COMEDI_VERSION_CODE COMEDI_VERSION(COMEDI_MAJORVERSION, \
  	COMEDI_MINORVERSION, COMEDI_MICROVERSION)
  #define COMEDI_RELEASE VERSION
  
  #define COMEDI_NUM_BOARD_MINORS 0x30
  
  /**
   * struct comedi_subdevice - Working data for a COMEDI subdevice
   * @device: COMEDI device to which this subdevice belongs.  (Initialized by
   *	comedi_alloc_subdevices().)
   * @index: Index of this subdevice within device's array of subdevices.
   *	(Initialized by comedi_alloc_subdevices().)
   * @type: Type of subdevice from &enum comedi_subdevice_type.  (Initialized by
   *	the low-level driver.)
   * @n_chan: Number of channels the subdevice supports.  (Initialized by the
   *	low-level driver.)
   * @subdev_flags: Various "SDF" flags indicating aspects of the subdevice to
   *	the COMEDI core and user application.  (Initialized by the low-level
   *	driver.)
   * @len_chanlist: Maximum length of a channel list if the subdevice supports
   *	asynchronous acquisition commands.  (Optionally initialized by the
   *	low-level driver, or changed from 0 to 1 during post-configuration.)
   * @private: Private data pointer which is either set by the low-level driver
   *	itself, or by a call to comedi_alloc_spriv() which allocates storage.
   *	In the latter case, the storage is automatically freed after the
   *	low-level driver's "detach" handler is called for the device.
   *	(Initialized by the low-level driver.)
   * @async: Pointer to &struct comedi_async id the subdevice supports
   *	asynchronous acquisition commands.  (Allocated and initialized during
   *	post-configuration if needed.)
   * @lock: Pointer to a file object that performed a %COMEDI_LOCK ioctl on the
   *	subdevice.  (Initially NULL.)
   * @busy: Pointer to a file object that is performing an asynchronous
   *	acquisition command on the subdevice.  (Initially NULL.)
   * @runflags: Internal flags for use by COMEDI core, mostly indicating whether
   *	an asynchronous acquisition command is running.
   * @spin_lock: Generic spin-lock for use by the COMEDI core and the low-level
   *	driver.  (Initialized by comedi_alloc_subdevices().)
   * @io_bits: Bit-mask indicating the channel directions for a DIO subdevice
   *	with no more than 32 channels.  A '1' at a bit position indicates the
   *	corresponding channel is configured as an output.  (Initialized by the
   *	low-level driver for a DIO subdevice.  Forced to all-outputs during
   *	post-configuration for a digital output subdevice.)
   * @maxdata: If non-zero, this is the maximum raw data value of each channel.
   *	If zero, the maximum data value is channel-specific.  (Initialized by
   *	the low-level driver.)
   * @maxdata_list: If the maximum data value is channel-specific, this points
   *	to an array of maximum data values indexed by channel index.
   *	(Initialized by the low-level driver.)
   * @range_table: If non-NULL, this points to a COMEDI range table for the
   *	subdevice.  If NULL, the range table is channel-specific.  (Initialized
   *	by the low-level driver, will be set to an "invalid" range table during
   *	post-configuration if @range_table and @range_table_list are both
   *	NULL.)
   * @range_table_list: If the COMEDI range table is channel-specific, this
   *	points to an array of pointers to COMEDI range tables indexed by
   *	channel number.  (Initialized by the low-level driver.)
   * @chanlist: Not used.
   * @insn_read: Optional pointer to a handler for the %INSN_READ instruction.
   *	(Initialized by the low-level driver, or set to a default handler
   *	during post-configuration.)
   * @insn_write: Optional pointer to a handler for the %INSN_WRITE instruction.
   *	(Initialized by the low-level driver, or set to a default handler
   *	during post-configuration.)
   * @insn_bits: Optional pointer to a handler for the %INSN_BITS instruction
   *	for a digital input, digital output or digital input/output subdevice.
   *	(Initialized by the low-level driver, or set to a default handler
   *	during post-configuration.)
   * @insn_config: Optional pointer to a handler for the %INSN_CONFIG
   *	instruction.  (Initialized by the low-level driver, or set to a default
   *	handler during post-configuration.)
   * @do_cmd: If the subdevice supports asynchronous acquisition commands, this
   *	points to a handler to set it up in hardware.  (Initialized by the
   *	low-level driver.)
   * @do_cmdtest: If the subdevice supports asynchronous acquisition commands,
   *	this points to a handler used to check and possibly tweak a prospective
   *	acquisition command without setting it up in hardware.  (Initialized by
   *	the low-level driver.)
   * @poll: If the subdevice supports asynchronous acquisition commands, this
   *	is an optional pointer to a handler for the %COMEDI_POLL ioctl which
   *	instructs the low-level driver to synchronize buffers.  (Initialized by
   *	the low-level driver if needed.)
   * @cancel: If the subdevice supports asynchronous acquisition commands, this
   *	points to a handler used to terminate a running command.  (Initialized
   *	by the low-level driver.)
   * @buf_change: If the subdevice supports asynchronous acquisition commands,
   *	this is an optional pointer to a handler that is called when the data
   *	buffer for handling asynchronous commands is allocated or reallocated.
   *	(Initialized by the low-level driver if needed.)
   * @munge: If the subdevice supports asynchronous acquisition commands and
   *	uses DMA to transfer data from the hardware to the acquisition buffer,
   *	this points to a function used to "munge" the data values from the
   *	hardware into the format expected by COMEDI.  (Initialized by the
   *	low-level driver if needed.)
   * @async_dma_dir: If the subdevice supports asynchronous acquisition commands
   *	and uses DMA to transfer data from the hardware to the acquisition
   *	buffer, this sets the DMA direction for the buffer. (initialized to
   *	%DMA_NONE by comedi_alloc_subdevices() and changed by the low-level
   *	driver if necessary.)
   * @state: Handy bit-mask indicating the output states for a DIO or digital
   *	output subdevice with no more than 32 channels. (Initialized by the
   *	low-level driver.)
   * @class_dev: If the subdevice supports asynchronous acquisition commands,
   *	this points to a sysfs comediX_subdY device where X is the minor device
   *	number of the COMEDI device and Y is the subdevice number.  The minor
   *	device number for the sysfs device is allocated dynamically in the
   *	range 48 to 255.  This is used to allow the COMEDI device to be opened
   *	with a different default read or write subdevice.  (Allocated during
   *	post-configuration if needed.)
   * @minor: If @class_dev is set, this is its dynamically allocated minor
   *	device number.  (Set during post-configuration if necessary.)
   * @readback: Optional pointer to memory allocated by
   *	comedi_alloc_subdev_readback() used to hold the values written to
   *	analog output channels so they can be read back.  The storage is
   *	automatically freed after the low-level driver's "detach" handler is
   *	called for the device.  (Initialized by the low-level driver.)
   *
   * This is the main control structure for a COMEDI subdevice.  If the subdevice
   * supports asynchronous acquisition commands, additional information is stored
   * in the &struct comedi_async pointed to by @async.
   *
   * Most of the subdevice is initialized by the low-level driver's "attach" or
   * "auto_attach" handlers but parts of it are initialized by
   * comedi_alloc_subdevices(), and other parts are initialized during
   * post-configuration on return from that handler.
   *
   * A low-level driver that sets @insn_bits for a digital input, digital output,
   * or DIO subdevice may leave @insn_read and @insn_write uninitialized, in
   * which case they will be set to a default handler during post-configuration
   * that uses @insn_bits to emulate the %INSN_READ and %INSN_WRITE instructions.
   */
  struct comedi_subdevice {
  	struct comedi_device *device;
  	int index;
  	int type;
  	int n_chan;
  	int subdev_flags;
  	int len_chanlist;	/* maximum length of channel/gain list */
  
  	void *private;
  
  	struct comedi_async *async;
  
  	void *lock;
  	void *busy;
  	unsigned int runflags;
  	spinlock_t spin_lock;	/* generic spin-lock for COMEDI and drivers */
  
  	unsigned int io_bits;
  
  	unsigned int maxdata;	/* if maxdata==0, use list */
  	const unsigned int *maxdata_list;	/* list is channel specific */
  
  	const struct comedi_lrange *range_table;
  	const struct comedi_lrange *const *range_table_list;
  
  	unsigned int *chanlist;	/* driver-owned chanlist (not used) */
  
  	int (*insn_read)(struct comedi_device *, struct comedi_subdevice *,
  			 struct comedi_insn *, unsigned int *);
  	int (*insn_write)(struct comedi_device *, struct comedi_subdevice *,
  			  struct comedi_insn *, unsigned int *);
  	int (*insn_bits)(struct comedi_device *, struct comedi_subdevice *,
  			 struct comedi_insn *, unsigned int *);
  	int (*insn_config)(struct comedi_device *, struct comedi_subdevice *,
  			   struct comedi_insn *, unsigned int *);
  
  	int (*do_cmd)(struct comedi_device *, struct comedi_subdevice *);
  	int (*do_cmdtest)(struct comedi_device *, struct comedi_subdevice *,
  			  struct comedi_cmd *);
  	int (*poll)(struct comedi_device *, struct comedi_subdevice *);
  	int (*cancel)(struct comedi_device *, struct comedi_subdevice *);
  
  	/* called when the buffer changes */
  	int (*buf_change)(struct comedi_device *, struct comedi_subdevice *);
  
  	void (*munge)(struct comedi_device *dev, struct comedi_subdevice *s,
  		      void *data, unsigned int num_bytes,
  		      unsigned int start_chan_index);
  	enum dma_data_direction async_dma_dir;
  
  	unsigned int state;
  
  	struct device *class_dev;
  	int minor;
  
  	unsigned int *readback;
  };
  
  /**
   * struct comedi_buf_page - Describe a page of a COMEDI buffer
   * @virt_addr: Kernel address of page.
   * @dma_addr: DMA address of page if in DMA coherent memory.
   */
  struct comedi_buf_page {
  	void *virt_addr;
  	dma_addr_t dma_addr;
  };
  
  /**
   * struct comedi_buf_map - Describe pages in a COMEDI buffer
   * @dma_hw_dev: Low-level hardware &struct device pointer copied from the
   *	COMEDI device's hw_dev member.
   * @page_list: Pointer to array of &struct comedi_buf_page, one for each
   *	page in the buffer.
   * @n_pages: Number of pages in the buffer.
   * @dma_dir: DMA direction used to allocate pages of DMA coherent memory,
   *	or %DMA_NONE if pages allocated from regular memory.
   * @refcount: &struct kref reference counter used to free the buffer.
   *
   * A COMEDI data buffer is allocated as individual pages, either in
   * conventional memory or DMA coherent memory, depending on the attached,
   * low-level hardware device.  (The buffer pages also get mapped into the
   * kernel's contiguous virtual address space pointed to by the 'prealloc_buf'
   * member of &struct comedi_async.)
   *
   * The buffer is normally freed when the COMEDI device is detached from the
   * low-level driver (which may happen due to device removal), but if it happens
   * to be mmapped at the time, the pages cannot be freed until the buffer has
   * been munmapped.  That is what the reference counter is for.  (The virtual
   * address space pointed by 'prealloc_buf' is freed when the COMEDI device is
   * detached.)
   */
  struct comedi_buf_map {
  	struct device *dma_hw_dev;
  	struct comedi_buf_page *page_list;
  	unsigned int n_pages;
  	enum dma_data_direction dma_dir;
  	struct kref refcount;
  };
  
  /**
   * struct comedi_async - Control data for asynchronous COMEDI commands
   * @prealloc_buf: Kernel virtual address of allocated acquisition buffer.
   * @prealloc_bufsz: Buffer size (in bytes).
   * @buf_map: Map of buffer pages.
   * @max_bufsize: Maximum allowed buffer size (in bytes).
   * @buf_write_count: "Write completed" count (in bytes, modulo 2**32).
   * @buf_write_alloc_count: "Allocated for writing" count (in bytes,
   *	modulo 2**32).
   * @buf_read_count: "Read completed" count (in bytes, modulo 2**32).
   * @buf_read_alloc_count: "Allocated for reading" count (in bytes,
   *	modulo 2**32).
   * @buf_write_ptr: Buffer position for writer.
   * @buf_read_ptr: Buffer position for reader.
   * @cur_chan: Current position in chanlist for scan (for those drivers that
   *	use it).
   * @scans_done: The number of scans completed.
   * @scan_progress: Amount received or sent for current scan (in bytes).
   * @munge_chan: Current position in chanlist for "munging".
   * @munge_count: "Munge" count (in bytes, modulo 2**32).
   * @munge_ptr: Buffer position for "munging".
   * @events: Bit-vector of events that have occurred.
   * @cmd: Details of comedi command in progress.
   * @wait_head: Task wait queue for file reader or writer.
   * @cb_mask: Bit-vector of events that should wake waiting tasks.
   * @inttrig: Software trigger function for command, or NULL.
   *
   * Note about the ..._count and ..._ptr members:
   *
   * Think of the _Count values being integers of unlimited size, indexing
   * into a buffer of infinite length (though only an advancing portion
   * of the buffer of fixed length prealloc_bufsz is accessible at any
   * time).  Then:
   *
   *   Buf_Read_Count <= Buf_Read_Alloc_Count <= Munge_Count <=
   *   Buf_Write_Count <= Buf_Write_Alloc_Count <=
   *   (Buf_Read_Count + prealloc_bufsz)
   *
   * (Those aren't the actual members, apart from prealloc_bufsz.) When the
   * buffer is reset, those _Count values start at 0 and only increase in value,
   * maintaining the above inequalities until the next time the buffer is
   * reset.  The buffer is divided into the following regions by the inequalities:
   *
   *   [0, Buf_Read_Count):
   *     old region no longer accessible
   *
   *   [Buf_Read_Count, Buf_Read_Alloc_Count):
   *     filled and munged region allocated for reading but not yet read
   *
   *   [Buf_Read_Alloc_Count, Munge_Count):
   *     filled and munged region not yet allocated for reading
   *
   *   [Munge_Count, Buf_Write_Count):
   *     filled region not yet munged
   *
   *   [Buf_Write_Count, Buf_Write_Alloc_Count):
   *     unfilled region allocated for writing but not yet written
   *
   *   [Buf_Write_Alloc_Count, Buf_Read_Count + prealloc_bufsz):
   *     unfilled region not yet allocated for writing
   *
   *   [Buf_Read_Count + prealloc_bufsz, infinity):
   *     unfilled region not yet accessible
   *
   * Data needs to be written into the buffer before it can be read out,
   * and may need to be converted (or "munged") between the two
   * operations.  Extra unfilled buffer space may need to allocated for
   * writing (advancing Buf_Write_Alloc_Count) before new data is written.
   * After writing new data, the newly filled space needs to be released
   * (advancing Buf_Write_Count).  This also results in the new data being
   * "munged" (advancing Munge_Count).  Before data is read out of the
   * buffer, extra space may need to be allocated for reading (advancing
   * Buf_Read_Alloc_Count).  After the data has been read out, the space
   * needs to be released (advancing Buf_Read_Count).
   *
   * The actual members, buf_read_count, buf_read_alloc_count,
   * munge_count, buf_write_count, and buf_write_alloc_count take the
   * value of the corresponding capitalized _Count values modulo 2^32
   * (UINT_MAX+1).  Subtracting a "higher" _count value from a "lower"
   * _count value gives the same answer as subtracting a "higher" _Count
   * value from a lower _Count value because prealloc_bufsz < UINT_MAX+1.
   * The modulo operation is done implicitly.
   *
   * The buf_read_ptr, munge_ptr, and buf_write_ptr members take the value
   * of the corresponding capitalized _Count values modulo prealloc_bufsz.
   * These correspond to byte indices in the physical buffer.  The modulo
   * operation is done by subtracting prealloc_bufsz when the value
   * exceeds prealloc_bufsz (assuming prealloc_bufsz plus the increment is
   * less than or equal to UINT_MAX).
   */
  struct comedi_async {
  	void *prealloc_buf;
  	unsigned int prealloc_bufsz;
  	struct comedi_buf_map *buf_map;
  	unsigned int max_bufsize;
  	unsigned int buf_write_count;
  	unsigned int buf_write_alloc_count;
  	unsigned int buf_read_count;
  	unsigned int buf_read_alloc_count;
  	unsigned int buf_write_ptr;
  	unsigned int buf_read_ptr;
  	unsigned int cur_chan;
  	unsigned int scans_done;
  	unsigned int scan_progress;
  	unsigned int munge_chan;
  	unsigned int munge_count;
  	unsigned int munge_ptr;
  	unsigned int events;
  	struct comedi_cmd cmd;
  	wait_queue_head_t wait_head;
  	unsigned int cb_mask;
  	int (*inttrig)(struct comedi_device *dev, struct comedi_subdevice *s,
  		       unsigned int x);
  };
  
  /**
   * enum comedi_cb - &struct comedi_async callback "events"
   * @COMEDI_CB_EOS:		end-of-scan
   * @COMEDI_CB_EOA:		end-of-acquisition/output
   * @COMEDI_CB_BLOCK:		data has arrived, wakes up read() / write()
   * @COMEDI_CB_EOBUF:		DEPRECATED: end of buffer
   * @COMEDI_CB_ERROR:		card error during acquisition
   * @COMEDI_CB_OVERFLOW:		buffer overflow/underflow
   * @COMEDI_CB_ERROR_MASK:	events that indicate an error has occurred
   * @COMEDI_CB_CANCEL_MASK:	events that will cancel an async command
   */
  enum comedi_cb {
  	COMEDI_CB_EOS		= BIT(0),
  	COMEDI_CB_EOA		= BIT(1),
  	COMEDI_CB_BLOCK		= BIT(2),
  	COMEDI_CB_EOBUF		= BIT(3),
  	COMEDI_CB_ERROR		= BIT(4),
  	COMEDI_CB_OVERFLOW	= BIT(5),
  	/* masks */
  	COMEDI_CB_ERROR_MASK	= (COMEDI_CB_ERROR | COMEDI_CB_OVERFLOW),
  	COMEDI_CB_CANCEL_MASK	= (COMEDI_CB_EOA | COMEDI_CB_ERROR_MASK)
  };
  
  /**
   * struct comedi_driver - COMEDI driver registration
   * @driver_name: Name of driver.
   * @module: Owning module.
   * @attach: The optional "attach" handler for manually configured COMEDI
   *	devices.
   * @detach: The "detach" handler for deconfiguring COMEDI devices.
   * @auto_attach: The optional "auto_attach" handler for automatically
   *	configured COMEDI devices.
   * @num_names: Optional number of "board names" supported.
   * @board_name: Optional pointer to a pointer to a board name.  The pointer
   *	to a board name is embedded in an element of a driver-defined array
   *	of static, read-only board type information.
   * @offset: Optional size of each element of the driver-defined array of
   *	static, read-only board type information, i.e. the offset between each
   *	pointer to a board name.
   *
   * This is used with comedi_driver_register() and comedi_driver_unregister() to
   * register and unregister a low-level COMEDI driver with the COMEDI core.
   *
   * If @num_names is non-zero, @board_name should be non-NULL, and @offset
   * should be at least sizeof(*board_name).  These are used by the handler for
   * the %COMEDI_DEVCONFIG ioctl to match a hardware device and its driver by
   * board name.  If @num_names is zero, the %COMEDI_DEVCONFIG ioctl matches a
   * hardware device and its driver by driver name.  This is only useful if the
   * @attach handler is set.  If @num_names is non-zero, the driver's @attach
   * handler will be called with the COMEDI device structure's board_ptr member
   * pointing to the matched pointer to a board name within the driver's private
   * array of static, read-only board type information.
   */
  struct comedi_driver {
  	/* private: */
  	struct comedi_driver *next;	/* Next in list of COMEDI drivers. */
  	/* public: */
  	const char *driver_name;
  	struct module *module;
  	int (*attach)(struct comedi_device *, struct comedi_devconfig *);
  	void (*detach)(struct comedi_device *);
  	int (*auto_attach)(struct comedi_device *, unsigned long);
  	unsigned int num_names;
  	const char *const *board_name;
  	int offset;
  };
  
  /**
   * struct comedi_device - Working data for a COMEDI device
   * @use_count: Number of open file objects.
   * @driver: Low-level COMEDI driver attached to this COMEDI device.
   * @pacer: Optional pointer to a dynamically allocated acquisition pacer
   *	control.  It is freed automatically after the COMEDI device is
   *	detached from the low-level driver.
   * @private: Optional pointer to private data allocated by the low-level
   *	driver.  It is freed automatically after the COMEDI device is
   *	detached from the low-level driver.
   * @class_dev: Sysfs comediX device.
   * @minor: Minor device number of COMEDI char device (0-47).
   * @detach_count: Counter incremented every time the COMEDI device is detached.
   *	Used for checking a previous attachment is still valid.
   * @hw_dev: Optional pointer to the low-level hardware &struct device.  It is
   *	required for automatically configured COMEDI devices and optional for
   *	COMEDI devices configured by the %COMEDI_DEVCONFIG ioctl, although
   *	the bus-specific COMEDI functions only work if it is set correctly.
   *	It is also passed to dma_alloc_coherent() for COMEDI subdevices that
   *	have their 'async_dma_dir' member set to something other than
   *	%DMA_NONE.
   * @board_name: Pointer to a COMEDI board name or a COMEDI driver name.  When
   *	the low-level driver's "attach" handler is called by the handler for
   *	the %COMEDI_DEVCONFIG ioctl, it either points to a matched board name
   *	string if the 'num_names' member of the &struct comedi_driver is
   *	non-zero, otherwise it points to the low-level driver name string.
   *	When the low-lever driver's "auto_attach" handler is called for an
   *	automatically configured COMEDI device, it points to the low-level
   *	driver name string.  The low-level driver is free to change it in its
   *	"attach" or "auto_attach" handler if it wishes.
   * @board_ptr: Optional pointer to private, read-only board type information in
   *	the low-level driver.  If the 'num_names' member of the &struct
   *	comedi_driver is non-zero, the handler for the %COMEDI_DEVCONFIG ioctl
   *	will point it to a pointer to a matched board name string within the
   *	driver's private array of static, read-only board type information when
   *	calling the driver's "attach" handler.  The low-level driver is free to
   *	change it.
   * @attached: Flag indicating that the COMEDI device is attached to a low-level
   *	driver.
   * @ioenabled: Flag used to indicate that a PCI device has been enabled and
   *	its regions requested.
   * @spinlock: Generic spin-lock for use by the low-level driver.
   * @mutex: Generic mutex for use by the COMEDI core module.
   * @attach_lock: &struct rw_semaphore used to guard against the COMEDI device
   *	being detached while an operation is in progress.  The down_write()
   *	operation is only allowed while @mutex is held and is used when
   *	changing @attached and @detach_count and calling the low-level driver's
   *	"detach" handler.  The down_read() operation is generally used without
   *	holding @mutex.
   * @refcount: &struct kref reference counter for freeing COMEDI device.
   * @n_subdevices: Number of COMEDI subdevices allocated by the low-level
   *	driver for this device.
   * @subdevices: Dynamically allocated array of COMEDI subdevices.
   * @mmio: Optional pointer to a remapped MMIO region set by the low-level
   *	driver.
   * @iobase: Optional base of an I/O port region requested by the low-level
   *	driver.
   * @iolen: Length of I/O port region requested at @iobase.
   * @irq: Optional IRQ number requested by the low-level driver.
   * @read_subdev: Optional pointer to a default COMEDI subdevice operated on by
   *	the read() file operation.  Set by the low-level driver.
   * @write_subdev: Optional pointer to a default COMEDI subdevice operated on by
   *	the write() file operation.  Set by the low-level driver.
   * @async_queue: Storage for fasync_helper().
   * @open: Optional pointer to a function set by the low-level driver to be
   *	called when @use_count changes from 0 to 1.
   * @close: Optional pointer to a function set by the low-level driver to be
   *	called when @use_count changed from 1 to 0.
   *
   * This is the main control data structure for a COMEDI device (as far as the
   * COMEDI core is concerned).  There are two groups of COMEDI devices -
   * "legacy" devices that are configured by the handler for the
   * %COMEDI_DEVCONFIG ioctl, and automatically configured devices resulting
   * from a call to comedi_auto_config() as a result of a bus driver probe in
   * a low-level COMEDI driver.  The "legacy" COMEDI devices are allocated
   * during module initialization if the "comedi_num_legacy_minors" module
   * parameter is non-zero and use minor device numbers from 0 to
   * comedi_num_legacy_minors minus one.  The automatically configured COMEDI
   * devices are allocated on demand and use minor device numbers from
   * comedi_num_legacy_minors to 47.
   */
  struct comedi_device {
  	int use_count;
  	struct comedi_driver *driver;
  	struct comedi_8254 *pacer;
  	void *private;
  
  	struct device *class_dev;
  	int minor;
  	unsigned int detach_count;
  	struct device *hw_dev;
  
  	const char *board_name;
  	const void *board_ptr;
  	bool attached:1;
  	bool ioenabled:1;
  	spinlock_t spinlock;	/* generic spin-lock for low-level driver */
  	struct mutex mutex;	/* generic mutex for COMEDI core */
  	struct rw_semaphore attach_lock;
  	struct kref refcount;
  
  	int n_subdevices;
  	struct comedi_subdevice *subdevices;
  
  	/* dumb */
  	void __iomem *mmio;
  	unsigned long iobase;
  	unsigned long iolen;
  	unsigned int irq;
  
  	struct comedi_subdevice *read_subdev;
  	struct comedi_subdevice *write_subdev;
  
  	struct fasync_struct *async_queue;
  
  	int (*open)(struct comedi_device *dev);
  	void (*close)(struct comedi_device *dev);
  };
  
  /*
   * function prototypes
   */
  
  void comedi_event(struct comedi_device *dev, struct comedi_subdevice *s);
  
  struct comedi_device *comedi_dev_get_from_minor(unsigned int minor);
  int comedi_dev_put(struct comedi_device *dev);
  
  bool comedi_is_subdevice_running(struct comedi_subdevice *s);
  
  void *comedi_alloc_spriv(struct comedi_subdevice *s, size_t size);
  void comedi_set_spriv_auto_free(struct comedi_subdevice *s);
  
  int comedi_check_chanlist(struct comedi_subdevice *s,
  			  int n,
  			  unsigned int *chanlist);
  
  /* range stuff */
  
  #define RANGE(a, b)		{(a) * 1e6, (b) * 1e6, 0}
  #define RANGE_ext(a, b)		{(a) * 1e6, (b) * 1e6, RF_EXTERNAL}
  #define RANGE_mA(a, b)		{(a) * 1e6, (b) * 1e6, UNIT_mA}
  #define RANGE_unitless(a, b)	{(a) * 1e6, (b) * 1e6, 0}
  #define BIP_RANGE(a)		{-(a) * 1e6, (a) * 1e6, 0}
  #define UNI_RANGE(a)		{0, (a) * 1e6, 0}
  
  extern const struct comedi_lrange range_bipolar10;
  extern const struct comedi_lrange range_bipolar5;
  extern const struct comedi_lrange range_bipolar2_5;
  extern const struct comedi_lrange range_unipolar10;
  extern const struct comedi_lrange range_unipolar5;
  extern const struct comedi_lrange range_unipolar2_5;
  extern const struct comedi_lrange range_0_20mA;
  extern const struct comedi_lrange range_4_20mA;
  extern const struct comedi_lrange range_0_32mA;
  extern const struct comedi_lrange range_unknown;
  
  #define range_digital		range_unipolar5
  
  #if __GNUC__ >= 3
  #define GCC_ZERO_LENGTH_ARRAY
  #else
  #define GCC_ZERO_LENGTH_ARRAY 0
  #endif
  
  /**
   * struct comedi_lrange - Describes a COMEDI range table
   * @length: Number of entries in the range table.
   * @range: Array of &struct comedi_krange, one for each range.
   *
   * Each element of @range[] describes the minimum and maximum physical range
   * range and the type of units.  Typically, the type of unit is %UNIT_volt
   * (i.e. volts) and the minimum and maximum are in millionths of a volt.
   * There may also be a flag that indicates the minimum and maximum are merely
   * scale factors for an unknown, external reference.
   */
  struct comedi_lrange {
  	int length;
  	struct comedi_krange range[GCC_ZERO_LENGTH_ARRAY];
  };
  
  /**
   * comedi_range_is_bipolar() - Test if subdevice range is bipolar
   * @s: COMEDI subdevice.
   * @range: Index of range within a range table.
   *
   * Tests whether a range is bipolar by checking whether its minimum value
   * is negative.
   *
   * Assumes @range is valid.  Does not work for subdevices using a
   * channel-specific range table list.
   *
   * Return:
   *	%true if the range is bipolar.
   *	%false if the range is unipolar.
   */
  static inline bool comedi_range_is_bipolar(struct comedi_subdevice *s,
  					   unsigned int range)
  {
  	return s->range_table->range[range].min < 0;
  }
  
  /**
   * comedi_range_is_unipolar() - Test if subdevice range is unipolar
   * @s: COMEDI subdevice.
   * @range: Index of range within a range table.
   *
   * Tests whether a range is unipolar by checking whether its minimum value
   * is at least 0.
   *
   * Assumes @range is valid.  Does not work for subdevices using a
   * channel-specific range table list.
   *
   * Return:
   *	%true if the range is unipolar.
   *	%false if the range is bipolar.
   */
  static inline bool comedi_range_is_unipolar(struct comedi_subdevice *s,
  					    unsigned int range)
  {
  	return s->range_table->range[range].min >= 0;
  }
  
  /**
   * comedi_range_is_external() - Test if subdevice range is external
   * @s: COMEDI subdevice.
   * @range: Index of range within a range table.
   *
   * Tests whether a range is externally reference by checking whether its
   * %RF_EXTERNAL flag is set.
   *
   * Assumes @range is valid.  Does not work for subdevices using a
   * channel-specific range table list.
   *
   * Return:
   *	%true if the range is external.
   *	%false if the range is internal.
   */
  static inline bool comedi_range_is_external(struct comedi_subdevice *s,
  					    unsigned int range)
  {
  	return !!(s->range_table->range[range].flags & RF_EXTERNAL);
  }
  
  /**
   * comedi_chan_range_is_bipolar() - Test if channel-specific range is bipolar
   * @s: COMEDI subdevice.
   * @chan: The channel number.
   * @range: Index of range within a range table.
   *
   * Tests whether a range is bipolar by checking whether its minimum value
   * is negative.
   *
   * Assumes @chan and @range are valid.  Only works for subdevices with a
   * channel-specific range table list.
   *
   * Return:
   *	%true if the range is bipolar.
   *	%false if the range is unipolar.
   */
  static inline bool comedi_chan_range_is_bipolar(struct comedi_subdevice *s,
  						unsigned int chan,
  						unsigned int range)
  {
  	return s->range_table_list[chan]->range[range].min < 0;
  }
  
  /**
   * comedi_chan_range_is_unipolar() - Test if channel-specific range is unipolar
   * @s: COMEDI subdevice.
   * @chan: The channel number.
   * @range: Index of range within a range table.
   *
   * Tests whether a range is unipolar by checking whether its minimum value
   * is at least 0.
   *
   * Assumes @chan and @range are valid.  Only works for subdevices with a
   * channel-specific range table list.
   *
   * Return:
   *	%true if the range is unipolar.
   *	%false if the range is bipolar.
   */
  static inline bool comedi_chan_range_is_unipolar(struct comedi_subdevice *s,
  						 unsigned int chan,
  						 unsigned int range)
  {
  	return s->range_table_list[chan]->range[range].min >= 0;
  }
  
  /**
   * comedi_chan_range_is_external() - Test if channel-specific range is external
   * @s: COMEDI subdevice.
   * @chan: The channel number.
   * @range: Index of range within a range table.
   *
   * Tests whether a range is externally reference by checking whether its
   * %RF_EXTERNAL flag is set.
   *
   * Assumes @chan and @range are valid.  Only works for subdevices with a
   * channel-specific range table list.
   *
   * Return:
   *	%true if the range is bipolar.
   *	%false if the range is unipolar.
   */
  static inline bool comedi_chan_range_is_external(struct comedi_subdevice *s,
  						 unsigned int chan,
  						 unsigned int range)
  {
  	return !!(s->range_table_list[chan]->range[range].flags & RF_EXTERNAL);
  }
  
  /**
   * comedi_offset_munge() - Convert between offset binary and 2's complement
   * @s: COMEDI subdevice.
   * @val: Value to be converted.
   *
   * Toggles the highest bit of a sample value to toggle between offset binary
   * and 2's complement.  Assumes that @s->maxdata is a power of 2 minus 1.
   *
   * Return: The converted value.
   */
  static inline unsigned int comedi_offset_munge(struct comedi_subdevice *s,
  					       unsigned int val)
  {
  	return val ^ s->maxdata ^ (s->maxdata >> 1);
  }
  
  /**
   * comedi_bytes_per_sample() - Determine subdevice sample size
   * @s: COMEDI subdevice.
   *
   * The sample size will be 4 (sizeof int) or 2 (sizeof short) depending on
   * whether the %SDF_LSAMPL subdevice flag is set or not.
   *
   * Return: The subdevice sample size.
   */
  static inline unsigned int comedi_bytes_per_sample(struct comedi_subdevice *s)
  {
  	return s->subdev_flags & SDF_LSAMPL ? sizeof(int) : sizeof(short);
  }
  
  /**
   * comedi_sample_shift() - Determine log2 of subdevice sample size
   * @s: COMEDI subdevice.
   *
   * The sample size will be 4 (sizeof int) or 2 (sizeof short) depending on
   * whether the %SDF_LSAMPL subdevice flag is set or not.  The log2 of the
   * sample size will be 2 or 1 and can be used as the right operand of a
   * bit-shift operator to multiply or divide something by the sample size.
   *
   * Return: log2 of the subdevice sample size.
   */
  static inline unsigned int comedi_sample_shift(struct comedi_subdevice *s)
  {
  	return s->subdev_flags & SDF_LSAMPL ? 2 : 1;
  }
  
  /**
   * comedi_bytes_to_samples() - Convert a number of bytes to a number of samples
   * @s: COMEDI subdevice.
   * @nbytes: Number of bytes
   *
   * Return: The number of bytes divided by the subdevice sample size.
   */
  static inline unsigned int comedi_bytes_to_samples(struct comedi_subdevice *s,
  						   unsigned int nbytes)
  {
  	return nbytes >> comedi_sample_shift(s);
  }
  
  /**
   * comedi_samples_to_bytes() - Convert a number of samples to a number of bytes
   * @s: COMEDI subdevice.
   * @nsamples: Number of samples.
   *
   * Return: The number of samples multiplied by the subdevice sample size.
   * (Does not check for arithmetic overflow.)
   */
  static inline unsigned int comedi_samples_to_bytes(struct comedi_subdevice *s,
  						   unsigned int nsamples)
  {
  	return nsamples << comedi_sample_shift(s);
  }
  
  /**
   * comedi_check_trigger_src() - Trivially validate a comedi_cmd trigger source
   * @src: Pointer to the trigger source to validate.
   * @flags: Bitmask of valid %TRIG_* for the trigger.
   *
   * This is used in "step 1" of the do_cmdtest functions of comedi drivers
   * to validate the comedi_cmd triggers. The mask of the @src against the
   * @flags allows the userspace comedilib to pass all the comedi_cmd
   * triggers as %TRIG_ANY and get back a bitmask of the valid trigger sources.
   *
   * Return:
   *	0 if trigger sources in *@src are all supported.
   *	-EINVAL if any trigger source in *@src is unsupported.
   */
  static inline int comedi_check_trigger_src(unsigned int *src,
  					   unsigned int flags)
  {
  	unsigned int orig_src = *src;
  
  	*src = orig_src & flags;
  	if (*src == TRIG_INVALID || *src != orig_src)
  		return -EINVAL;
  	return 0;
  }
  
  /**
   * comedi_check_trigger_is_unique() - Make sure a trigger source is unique
   * @src: The trigger source to check.
   *
   * Return:
   *	0 if no more than one trigger source is set.
   *	-EINVAL if more than one trigger source is set.
   */
  static inline int comedi_check_trigger_is_unique(unsigned int src)
  {
  	/* this test is true if more than one _src bit is set */
  	if ((src & (src - 1)) != 0)
  		return -EINVAL;
  	return 0;
  }
  
  /**
   * comedi_check_trigger_arg_is() - Trivially validate a trigger argument
   * @arg: Pointer to the trigger arg to validate.
   * @val: The value the argument should be.
   *
   * Forces *@arg to be @val.
   *
   * Return:
   *	0 if *@arg was already @val.
   *	-EINVAL if *@arg differed from @val.
   */
  static inline int comedi_check_trigger_arg_is(unsigned int *arg,
  					      unsigned int val)
  {
  	if (*arg != val) {
  		*arg = val;
  		return -EINVAL;
  	}
  	return 0;
  }
  
  /**
   * comedi_check_trigger_arg_min() - Trivially validate a trigger argument min
   * @arg: Pointer to the trigger arg to validate.
   * @val: The minimum value the argument should be.
   *
   * Forces *@arg to be at least @val, setting it to @val if necessary.
   *
   * Return:
   *	0 if *@arg was already at least @val.
   *	-EINVAL if *@arg was less than @val.
   */
  static inline int comedi_check_trigger_arg_min(unsigned int *arg,
  					       unsigned int val)
  {
  	if (*arg < val) {
  		*arg = val;
  		return -EINVAL;
  	}
  	return 0;
  }
  
  /**
   * comedi_check_trigger_arg_max() - Trivially validate a trigger argument max
   * @arg: Pointer to the trigger arg to validate.
   * @val: The maximum value the argument should be.
   *
   * Forces *@arg to be no more than @val, setting it to @val if necessary.
   *
   * Return:
   *	0 if*@arg was already no more than @val.
   *	-EINVAL if *@arg was greater than @val.
   */
  static inline int comedi_check_trigger_arg_max(unsigned int *arg,
  					       unsigned int val)
  {
  	if (*arg > val) {
  		*arg = val;
  		return -EINVAL;
  	}
  	return 0;
  }
  
  /*
   * Must set dev->hw_dev if you wish to dma directly into comedi's buffer.
   * Also useful for retrieving a previously configured hardware device of
   * known bus type.  Set automatically for auto-configured devices.
   * Automatically set to NULL when detaching hardware device.
   */
  int comedi_set_hw_dev(struct comedi_device *dev, struct device *hw_dev);
  
  /**
   * comedi_buf_n_bytes_ready - Determine amount of unread data in buffer
   * @s: COMEDI subdevice.
   *
   * Determines the number of bytes of unread data in the asynchronous
   * acquisition data buffer for a subdevice.  The data in question might not
   * have been fully "munged" yet.
   *
   * Returns: The amount of unread data in bytes.
   */
  static inline unsigned int comedi_buf_n_bytes_ready(struct comedi_subdevice *s)
  {
  	return s->async->buf_write_count - s->async->buf_read_count;
  }
  
  unsigned int comedi_buf_write_alloc(struct comedi_subdevice *s, unsigned int n);
  unsigned int comedi_buf_write_free(struct comedi_subdevice *s, unsigned int n);
  
  unsigned int comedi_buf_read_n_available(struct comedi_subdevice *s);
  unsigned int comedi_buf_read_alloc(struct comedi_subdevice *s, unsigned int n);
  unsigned int comedi_buf_read_free(struct comedi_subdevice *s, unsigned int n);
  
  unsigned int comedi_buf_write_samples(struct comedi_subdevice *s,
  				      const void *data, unsigned int nsamples);
  unsigned int comedi_buf_read_samples(struct comedi_subdevice *s,
  				     void *data, unsigned int nsamples);
  
  /* drivers.c - general comedi driver functions */
  
  #define COMEDI_TIMEOUT_MS	1000
  
  int comedi_timeout(struct comedi_device *, struct comedi_subdevice *,
  		   struct comedi_insn *,
  		   int (*cb)(struct comedi_device *, struct comedi_subdevice *,
  			     struct comedi_insn *, unsigned long context),
  		   unsigned long context);
  
  unsigned int comedi_handle_events(struct comedi_device *dev,
  				  struct comedi_subdevice *s);
  
  int comedi_dio_insn_config(struct comedi_device *, struct comedi_subdevice *,
  			   struct comedi_insn *, unsigned int *data,
  			   unsigned int mask);
  unsigned int comedi_dio_update_state(struct comedi_subdevice *,
  				     unsigned int *data);
  unsigned int comedi_bytes_per_scan_cmd(struct comedi_subdevice *s,
  				       struct comedi_cmd *cmd);
  unsigned int comedi_bytes_per_scan(struct comedi_subdevice *s);
  unsigned int comedi_nscans_left(struct comedi_subdevice *s,
  				unsigned int nscans);
  unsigned int comedi_nsamples_left(struct comedi_subdevice *s,
  				  unsigned int nsamples);
  void comedi_inc_scan_progress(struct comedi_subdevice *s,
  			      unsigned int num_bytes);
  
  void *comedi_alloc_devpriv(struct comedi_device *, size_t);
  int comedi_alloc_subdevices(struct comedi_device *, int);
  int comedi_alloc_subdev_readback(struct comedi_subdevice *);
  
  int comedi_readback_insn_read(struct comedi_device *, struct comedi_subdevice *,
  			      struct comedi_insn *, unsigned int *data);
  
  int comedi_load_firmware(struct comedi_device *, struct device *,
  			 const char *name,
  			 int (*cb)(struct comedi_device *,
  				   const u8 *data, size_t size,
  				   unsigned long context),
  			 unsigned long context);
  
  int __comedi_request_region(struct comedi_device *,
  			    unsigned long start, unsigned long len);
  int comedi_request_region(struct comedi_device *,
  			  unsigned long start, unsigned long len);
  void comedi_legacy_detach(struct comedi_device *);
  
  int comedi_auto_config(struct device *, struct comedi_driver *,
  		       unsigned long context);
  void comedi_auto_unconfig(struct device *);
  
  int comedi_driver_register(struct comedi_driver *);
  void comedi_driver_unregister(struct comedi_driver *);
  
  /**
   * module_comedi_driver() - Helper macro for registering a comedi driver
   * @__comedi_driver: comedi_driver struct
   *
   * Helper macro for comedi drivers which do not do anything special in module
   * init/exit. This eliminates a lot of boilerplate. Each module may only use
   * this macro once, and calling it replaces module_init() and module_exit().
   */
  #define module_comedi_driver(__comedi_driver) \
  	module_driver(__comedi_driver, comedi_driver_register, \
  			comedi_driver_unregister)
  
  #endif /* _COMEDIDEV_H */
  