path: root/drivers/staging/comedi/comedidev.h

/*
 * 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 {
	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 runflags;
	spinlock_t spin_lock;

	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 {
	void *virt_addr;
	dma_addr_t dma_addr;
};

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:	preallocated buffer
 * @prealloc_bufsz:	buffer size (in bytes)
 * @buf_map:		map of buffer pages
 * @max_bufsize:	maximum 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 (COMEDI_CB_EOS)
 * @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;
	struct mutex mutex;
	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 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 {
	int length;
	struct comedi_krange range[GCC_ZERO_LENGTH_ARRAY];
};

static inline bool comedi_range_is_bipolar(struct comedi_subdevice *s,
					   unsigned int range)
{
	return s->range_table->range[range].min < 0;
}

static inline bool comedi_range_is_unipolar(struct comedi_subdevice *s,
					    unsigned int range)
{
	return s->range_table->range[range].min >= 0;
}

static inline bool comedi_range_is_external(struct comedi_subdevice *s,
					    unsigned int range)
{
	return !!(s->range_table->range[range].flags & RF_EXTERNAL);
}

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;
}

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;
}

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);
}

/* munge between offset binary and two's complement values */
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 struct
 *
 * The sample size will be 4 (sizeof int) or 2 (sizeof short) depending on
 * whether the SDF_LSAMPL subdevice flag is set or not.
 *
 * Returns 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 struct
 *
 * 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.
 *
 * Returns 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 - converts a number of bytes to a number of samples
 * @s:		comedi_subdevice struct
 * @nbytes:	number of bytes
 *
 * Returns 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 - converts a number of samples to a number of bytes
 * @s:		comedi_subdevice struct
 * @nsamples:	number of samples
 *
 * Returns 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 vaildate 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.
 */
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
 */
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
 */
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
 * @arg: pointer to the trigger arg to validate
 * @val: the minimum value the argument should be
 */
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
 * @arg: pointer to the trigger arg to validate
 * @val: the maximum value the argument should be
 */
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);

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(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 */