/*
    cb_pcidda.c
    This intends to be a driver for the ComputerBoards / MeasurementComputing
    PCI-DDA series.

	 Copyright (C) 2001 Ivan Martinez <ivanmr@altavista.com>
    Copyright (C) 2001 Frank Mori Hess <fmhess@uiuc.edu>

    COMEDI - Linux Control and Measurement Device Interface
    Copyright (C) 1997-8 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.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

*/
/*
Driver: cb_pcidda.o
Description: ComputerBoards/MeasurementComputing PCI-DDA series
Author: Ivan Martinez <ivanmr@altavista.com>, Frank Mori Hess <fmhess@users.sourceforge.net>
Status: Supports 08/16, 04/16, 02/16, 08/12, 04/12, and 02/12
Devices: [Measurement Computing] PCI-DDA08/12 (cb_pcidda), PCI-DDA04/12,
  PCI-DDA02/12, PCI-DDA08/16, PCI-DDA04/16, PCI-DDA02/16

Configuration options:
  [0] - PCI bus of device (optional)
  [1] - PCI slot of device (optional)
  If bus/slot is not specified, the first available PCI
  device will be used.

Only simple analog output writing is supported.

So far it has only been tested with:
  - PCI-DDA08/12
Please report sucess/failure with other different cards to
<comedi@comedi.org>.
*/

#include <linux/comedidev.h>
#include <linux/pci.h>

#include "8255.h"

#define PCI_VENDOR_ID_CB	0x1307	// PCI vendor number of ComputerBoards
#define N_BOARDS	10	// Number of boards in cb_pcidda_boards
#define EEPROM_SIZE	128	// number of entries in eeprom
#define MAX_AO_CHANNELS 8	// maximum number of ao channels for supported boards

/* PCI-DDA base addresses */
#define DIGITALIO_BADRINDEX	2
	// DIGITAL I/O is pci_dev->resource[2]
#define DIGITALIO_SIZE 8
	// DIGITAL I/O uses 8 I/O port addresses
#define DAC_BADRINDEX	3
	// DAC is pci_dev->resource[3]

/* Digital I/O registers */
#define PORT1A 0	// PORT 1A DATA

#define PORT1B 1	// PORT 1B DATA

#define PORT1C 2	// PORT 1C DATA

#define CONTROL1 3	// CONTROL REGISTER 1

#define PORT2A 4	// PORT 2A DATA

#define PORT2B 5	// PORT 2B DATA

#define PORT2C 6	// PORT 2C DATA

#define CONTROL2 7	// CONTROL REGISTER 2

/* DAC registers */
#define DACONTROL	0	// D/A CONTROL REGISTER
#define	SU	0000001	// Simultaneous update enabled
#define NOSU	0000000	// Simultaneous update disabled
#define	ENABLEDAC	0000002	// Enable specified DAC
#define	DISABLEDAC	0000000	// Disable specified DAC
#define RANGE2V5	0000000	// 2.5V
#define RANGE5V	0000200	// 5V
#define RANGE10V	0000300	// 10V
#define UNIP	0000400	// Unipolar outputs
#define BIP	0000000	// Bipolar outputs

#define DACALIBRATION1	4	// D/A CALIBRATION REGISTER 1
//write bits
#define	SERIAL_IN_BIT	0x1	// serial data input for eeprom, caldacs, reference dac
#define	CAL_CHANNEL_MASK	(0x7 << 1)
#define	CAL_CHANNEL_BITS(channel)	(((channel) << 1) & CAL_CHANNEL_MASK)
//read bits
#define	CAL_COUNTER_MASK	0x1f
#define	CAL_COUNTER_OVERFLOW_BIT	0x20	// calibration counter overflow status bit
#define	AO_BELOW_REF_BIT	0x40	// analog output is less than reference dac voltage
#define	SERIAL_OUT_BIT	0x80	// serial data out, for reading from eeprom

#define DACALIBRATION2	6 // D/A CALIBRATION REGISTER 2
#define	SELECT_EEPROM_BIT	0x1	// send serial data in to eeprom
#define	DESELECT_REF_DAC_BIT	0x2	// don't send serial data to MAX542 reference dac
#define	DESELECT_CALDAC_BIT(n)	(0x4 << (n))	// don't send serial data to caldac n
#define	DUMMY_BIT	0x40	// manual says to set this bit with no explanation

#define DADATA	8	// FIRST D/A DATA REGISTER (0)

static comedi_lrange cb_pcidda_ranges =
{
	6,
	{
		BIP_RANGE(10),
		BIP_RANGE(5),
		BIP_RANGE(2.5),
		UNI_RANGE(10),
		UNI_RANGE(5),
		UNI_RANGE(2.5),
	}
};

/*
 * Board descriptions for two imaginary boards.  Describing the
 * boards in this way is optional, and completely driver-dependent.
 * Some drivers use arrays such as this, other do not.
 */
typedef struct cb_pcidda_board_struct
{
	char *name;
	char status;		// Driver status:
				// 0 - tested
				// 1 - manual read, not tested
				// 2 - manual not read
	unsigned short device_id;
	int ao_chans;
	int ao_bits;
	comedi_lrange *ranges;
} cb_pcidda_board;
static cb_pcidda_board cb_pcidda_boards[] =
{
	{
		name:		"pci-dda02/12",
		status:		1,
		device_id:	0x20,
		ao_chans:	2,
		ao_bits:	12,
		ranges:	&cb_pcidda_ranges,
	},
	{
		name:		"pci-dda04/12",
		status:		1,
		device_id:	0x21,
		ao_chans:	4,
		ao_bits:	12,
		ranges:	&cb_pcidda_ranges,
	},
	{
		name:		"pci-dda08/12",
		status:		0,
		device_id:	0x22,
		ao_chans:	8,
		ao_bits:	12,
		ranges:	&cb_pcidda_ranges,
	},
	{
		name:		"pci-dda02/16",
		status:		2,
		device_id:	0x23,
		ao_chans:	2,
		ao_bits:	16,
		ranges:	&cb_pcidda_ranges,
	},
	{
		name:		"pci-dda04/16",
		status:		2,
		device_id:	0x24,
		ao_chans:	4,
		ao_bits:	16,
		ranges:	&cb_pcidda_ranges,
	},
	{
		name:		"pci-dda08/16",
		status:		0,
		device_id:	0x25,
		ao_chans:	8,
		ao_bits:	16,
		ranges:	&cb_pcidda_ranges,
	},
};

static struct pci_device_id cb_pcidda_pci_table[] __devinitdata = {
	{ PCI_VENDOR_ID_CB, 0x0020, PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0 },
	{ PCI_VENDOR_ID_CB, 0x0021, PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0 },
	{ PCI_VENDOR_ID_CB, 0x0022, PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0 },
	{ PCI_VENDOR_ID_CB, 0x0023, PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0 },
	{ PCI_VENDOR_ID_CB, 0x0024, PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0 },
	{ PCI_VENDOR_ID_CB, 0x0025, PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0 },
	{ 0 }
};
MODULE_DEVICE_TABLE(pci, cb_pcidda_pci_table);

/*
 * Useful for shorthand access to the particular board structure
 */
#define thisboard ((cb_pcidda_board *)dev->board_ptr)

/* this structure is for data unique to this hardware driver.  If
   several hardware drivers keep similar information in this structure,
   feel free to suggest moving the variable to the comedi_device struct.  */
typedef struct
{
	int data;

	/* would be useful for a PCI device */
	struct pci_dev *pci_dev;

	unsigned long digitalio;
	unsigned long dac;
	//unsigned long control_status;
	//unsigned long adc_fifo;
	unsigned int dac_cal1_bits;	// bits last written to da calibration register 1
	unsigned int ao_range[MAX_AO_CHANNELS];	// current range settings for output channels
	u16 eeprom_data[EEPROM_SIZE];	// software copy of board's eeprom
} cb_pcidda_private;

/*
 * most drivers define the following macro to make it easy to
 * access the private structure.
 */
#define devpriv ((cb_pcidda_private *)dev->private)

static int cb_pcidda_attach(comedi_device *dev,comedi_devconfig *it);
static int cb_pcidda_detach(comedi_device *dev);
//static int cb_pcidda_ai_rinsn(comedi_device *dev,comedi_subdevice *s,comedi_insn *insn,lsampl_t *data);
static int cb_pcidda_ao_winsn(comedi_device *dev,comedi_subdevice *s,comedi_insn *insn,lsampl_t *data);
//static int cb_pcidda_ai_cmd(comedi_device *dev,comedi_subdevice *s);
static int cb_pcidda_ai_cmdtest(comedi_device *dev,comedi_subdevice *s,
	comedi_cmd *cmd);
static int cb_pcidda_ns_to_timer(unsigned int *ns,int round);
static unsigned int cb_pcidda_serial_in(comedi_device *dev);
static void cb_pcidda_serial_out(comedi_device *dev, unsigned int value, unsigned int num_bits);
static unsigned int cb_pcidda_read_eeprom(comedi_device *dev, unsigned int address);
static void cb_pcidda_calibrate(comedi_device *dev, unsigned int channel, unsigned int range);

/*
 * The comedi_driver structure tells the Comedi core module
 * which functions to call to configure/deconfigure (attach/detach)
 * the board, and also about the kernel module that contains
 * the device code.
 */
static comedi_driver driver_cb_pcidda={
	driver_name:	"cb_pcidda",
	module:		THIS_MODULE,
	attach:		cb_pcidda_attach,
	detach:		cb_pcidda_detach,
};

/*
 * Attach is called by the Comedi core to configure the driver
 * for a particular board.
 */
static int cb_pcidda_attach(comedi_device *dev, comedi_devconfig *it)
{
	comedi_subdevice *s;
	struct pci_dev* pcidev;
	int index;
	unsigned int dac, digitalio;

	printk("comedi%d: cb_pcidda: ",dev->minor);

/*
 * Allocate the private structure area.
 */
	if(alloc_private(dev,sizeof(cb_pcidda_private))<0)
		return -ENOMEM;

/*
 * Probe the device to determine what device in the series it is.
 */
	printk("\n");

	pci_for_each_dev(pcidev){
		if(pcidev->vendor==PCI_VENDOR_ID_CB){
			if(it->options[0] || it->options[1]){
				if(pcidev->bus->number==it->options[0] &&
				   PCI_SLOT(pcidev->devfn)==it->options[1]){
					break;
				}
			}else{
				break;
			}
		}
	}

	if(!pcidev){
		printk("Not a ComputerBoards/MeasurementComputing card on requested position\n");
		return -EIO;
	}

	for(index=0;index<N_BOARDS;index++){
		if(cb_pcidda_boards[index].device_id == pcidev->device){
			goto found;
		}
	}
	printk("Not a supported ComputerBoards/MeasurementComputing card on "
		"requested position\n");			
	return -EIO;

found:
	devpriv->pci_dev = pcidev;
	dev->board_ptr = cb_pcidda_boards+index;
	// "thisboard" macro can be used from here.
	printk("Found %s at requested position\n",thisboard->name);

	/*
	 * Initialize devpriv->control_status and devpriv->adc_fifo to point to
	 * their base address.
	 */
	if(pci_enable_device(devpriv->pci_dev))
		return -EIO;
	digitalio = pci_resource_start(devpriv->pci_dev, DIGITALIO_BADRINDEX); 
	dac = pci_resource_start(devpriv->pci_dev, DAC_BADRINDEX); 

/*
 * Allocate the I/O ports.
 */
	if (check_region(digitalio, DIGITALIO_SIZE) < 0)
	{
		printk("I/O port conflict: failed to allocate ports 0x%x to 0x%x\n",
			digitalio, digitalio + DIGITALIO_SIZE - 1);
		return -EIO;
	}
	if (check_region(dac, 8 + thisboard->ao_chans*2) < 0)
	{
		printk("I/O port conflict: failed to allocate ports 0x%x to 0x%x\n",
			dac, dac + 7 + thisboard->ao_chans*2);
		return -EIO;
	}
	request_region(digitalio, DIGITALIO_SIZE, thisboard->name);
	devpriv->digitalio = digitalio;
	request_region(dac, 8 + thisboard->ao_chans*2,
		thisboard->name);
	devpriv->dac = dac;

/*
 * Warn about the status of the driver.
 */
	if (thisboard->status == 2)
		printk("WARNING: DRIVER FOR THIS BOARD NOT CHECKED WITH MANUAL. "
			"WORKS ASSUMING FULL COMPATIBILITY WITH PCI-DDA08/12. "
			"PLEASE REPORT USAGE TO <ivanmr@altavista.com>.\n");

/*
 * Initialize dev->board_name.
 */
	dev->board_name = thisboard->name;

/*
 * Allocate the subdevice structures.
 */
	dev->n_subdevices = 3;
	if(alloc_subdevices(dev) < 0)
		return -ENOMEM;

	s = dev->subdevices + 0;
	/* analog output subdevice */
	s->type = COMEDI_SUBD_AO;
	s->subdev_flags = SDF_WRITABLE;
	s->n_chan = thisboard->ao_chans;
	s->maxdata = (1 << thisboard->ao_bits) - 1;
	s->range_table = thisboard->ranges;
	s->insn_write = cb_pcidda_ao_winsn;
//	s->do_cmd = cb_pcidda_ai_cmd;
	s->do_cmdtest = cb_pcidda_ai_cmdtest;

	// two 8255 digital io subdevices
	s = dev->subdevices + 1;
	subdev_8255_init(dev, s, NULL, (unsigned long)(devpriv->digitalio));
	s = dev->subdevices + 2;
	subdev_8255_init(dev, s, NULL,
		(unsigned long)(devpriv->digitalio + PORT2A));

	printk(" eeprom:");
	for(index = 0; index < EEPROM_SIZE; index++)
	{
		devpriv->eeprom_data[index] = cb_pcidda_read_eeprom(dev, index);
		printk(" %i:0x%x ", index, devpriv->eeprom_data[index]);
	}
	printk("\n");

	// set calibrations dacs
	for(index = 0; index < thisboard->ao_chans; index++)
		cb_pcidda_calibrate(dev, index, devpriv->ao_range[index]);

	return 1;
}


/*
 * _detach is called to deconfigure a device.  It should deallocate
 * resources.
 * This function is also called when _attach() fails, so it should be
 * careful not to release resources that were not necessarily
 * allocated by _attach().  dev->private and dev->subdevices are
 * deallocated automatically by the core.
 */
static int cb_pcidda_detach(comedi_device *dev)
{
/*
 * Deallocate the I/O ports.
 */
	if(devpriv)
	{
		if(devpriv->digitalio)
			release_region(devpriv->digitalio, DIGITALIO_SIZE);
		if(devpriv->dac)
			release_region(devpriv->dac, 8 + thisboard->ao_chans*2);
	}
	// cleanup 8255
	if(dev->subdevices)
	{
		subdev_8255_cleanup(dev, dev->subdevices + 1);
		subdev_8255_cleanup(dev, dev->subdevices + 2);
	}

	printk("comedi%d: cb_pcidda: remove\n",dev->minor);

	return 0;
}


/*
 * I will program this later... ;-)
 *
static int cb_pcidda_ai_cmd(comedi_device *dev,comedi_subdevice *s)
{
	printk("cb_pcidda_ai_cmd\n");
	printk("subdev: %d\n", cmd->subdev);
	printk("flags: %d\n", cmd->flags);
	printk("start_src: %d\n", cmd->start_src);
	printk("start_arg: %d\n", cmd->start_arg);
	printk("scan_begin_src: %d\n", cmd->scan_begin_src);
	printk("convert_src: %d\n", cmd->convert_src);
	printk("convert_arg: %d\n", cmd->convert_arg);
	printk("scan_end_src: %d\n", cmd->scan_end_src);
	printk("scan_end_arg: %d\n", cmd->scan_end_arg);
	printk("stop_src: %d\n", cmd->stop_src);
	printk("stop_arg: %d\n", cmd->stop_arg);
	printk("chanlist_len: %d\n", cmd->chanlist_len);
}
*/

static int cb_pcidda_ai_cmdtest(comedi_device *dev,comedi_subdevice *s,
	comedi_cmd *cmd)
{
	int err=0;
	int tmp;

	/* cmdtest tests a particular command to see if it is valid.
	 * Using the cmdtest ioctl, a user can create a valid cmd
	 * and then have it executes by the cmd ioctl.
	 *
	 * cmdtest returns 1,2,3,4 or 0, depending on which tests
	 * the command passes. */

	/* step 1: make sure trigger sources are trivially valid */

	tmp = cmd->start_src;
	cmd->start_src &= TRIG_NOW;
	if(!cmd->start_src || tmp != cmd->start_src)
		err++;

	tmp = cmd->scan_begin_src;
	cmd->scan_begin_src &= TRIG_TIMER | TRIG_EXT;
	if(!cmd->scan_begin_src || tmp != cmd->scan_begin_src)
		err++;

	tmp = cmd->convert_src;
	cmd->convert_src &= TRIG_TIMER | TRIG_EXT;
	if(!cmd->convert_src || tmp != cmd->convert_src)
		err++;

	tmp = cmd->scan_end_src;
	cmd->scan_end_src &= TRIG_COUNT;
	if(!cmd->scan_end_src || tmp != cmd->scan_end_src)
		err++;

	tmp = cmd->stop_src;
	cmd->stop_src &= TRIG_COUNT | TRIG_NONE;
	if(!cmd->stop_src || tmp != cmd->stop_src)
		err++;

	if(err)return 1;

	/* step 2: make sure trigger sources are unique and mutually compatible */

	/* note that mutual compatiblity is not an issue here */
	if(cmd->scan_begin_src != TRIG_TIMER && cmd->scan_begin_src != TRIG_EXT)
		err++;
	if(cmd->convert_src != TRIG_TIMER && cmd->convert_src != TRIG_EXT)
		err++;
	if(cmd->stop_src != TRIG_TIMER && cmd->stop_src != TRIG_EXT)
		err++;

	if(err) return 2;

	/* step 3: make sure arguments are trivially compatible */

	if(cmd->start_arg!=0)
	{
		cmd->start_arg=0;
		err++;
	}

#define MAX_SPEED	10000		/* in nanoseconds */
#define MIN_SPEED	1000000000	/* in nanoseconds */

	if (cmd->scan_begin_src == TRIG_TIMER)
	{
		if (cmd->scan_begin_arg < MAX_SPEED)
		{
			cmd->scan_begin_arg = MAX_SPEED;
			err++;
		}
		if (cmd->scan_begin_arg > MIN_SPEED)
		{
			cmd->scan_begin_arg = MIN_SPEED;
			err++;
		}
	}
	else
	{
		/* external trigger */
		/* should be level/edge, hi/lo specification here */
		/* should specify multiple external triggers */
		if (cmd->scan_begin_arg > 9)
		{
			cmd->scan_begin_arg = 9;
			err++;
		}
	}
	if (cmd->convert_src == TRIG_TIMER)
	{
		if (cmd->convert_arg < MAX_SPEED)
		{
			cmd->convert_arg = MAX_SPEED;
			err++;
		}
		if (cmd->convert_arg>MIN_SPEED)
		{
			cmd->convert_arg = MIN_SPEED;
			err++;
		}
	}
	else
	{
		/* external trigger */
		/* see above */
		if (cmd->convert_arg > 9)
		{
			cmd->convert_arg = 9;
			err++;
		}
	}

	if(cmd->scan_end_arg != cmd->chanlist_len)
	{
		cmd->scan_end_arg = cmd->chanlist_len;
		err++;
	}
	if(cmd->stop_src == TRIG_COUNT)
	{
		if(cmd->stop_arg > 0x00ffffff)
		{
			cmd->stop_arg = 0x00ffffff;
			err++;
		}
	}
	else
	{
		/* TRIG_NONE */
		if (cmd->stop_arg != 0)
		{
			cmd->stop_arg=0;
			err++;
		}
	}

	if(err)return 3;

	/* step 4: fix up any arguments */

	if(cmd->scan_begin_src == TRIG_TIMER)
	{
		tmp = cmd->scan_begin_arg;
		cb_pcidda_ns_to_timer(&cmd->scan_begin_arg, cmd->flags & TRIG_ROUND_MASK);
		if(tmp != cmd->scan_begin_arg)
			err++;
	}
	if(cmd->convert_src == TRIG_TIMER)
	{
		tmp=cmd->convert_arg;
		cb_pcidda_ns_to_timer(&cmd->convert_arg, cmd->flags & TRIG_ROUND_MASK);
		if(tmp != cmd->convert_arg)
			err++;
		if(cmd->scan_begin_src == TRIG_TIMER &&
		  cmd->scan_begin_arg < cmd->convert_arg * cmd->scan_end_arg)
		{
			cmd->scan_begin_arg = cmd->convert_arg * cmd->scan_end_arg;
			err++;
		}
	}

	if(err) return 4;

	return 0;
}

/* This function doesn't require a particular form, this is just
 * what happens to be used in some of the drivers.  It should
 * convert ns nanoseconds to a counter value suitable for programming
 * the device.  Also, it should adjust ns so that it cooresponds to
 * the actual time that the device will use. */
static int cb_pcidda_ns_to_timer(unsigned int *ns,int round)
{
	/* trivial timer */
	return *ns;
}

static int cb_pcidda_ao_winsn(comedi_device *dev,comedi_subdevice *s,comedi_insn *insn,lsampl_t *data)
{
	unsigned int command;
	unsigned int channel, range;

	channel = CR_CHAN(insn->chanspec);
	range = CR_RANGE(insn->chanspec);

	// adjust calibration dacs if range has changed
	if(range != devpriv->ao_range[channel])
		cb_pcidda_calibrate(dev, channel, range);

	/* output channel configuration */
	command = NOSU | ENABLEDAC;

	/* output channel range */
	switch (range)
	{
		case 0:
			command |= BIP | RANGE10V;
			break;
		case 1:
			command |= BIP | RANGE5V;
			break;
		case 2:
			command |= BIP | RANGE2V5;
			break;
		case 3:
			command |= UNIP | RANGE10V;
			break;
		case 4:
			command |= UNIP | RANGE5V;
			break;
		case 5:
			command |= UNIP | RANGE2V5;
			break;
	};

	/* output channel specification */
	command |= channel << 2;
	outw(command, devpriv->dac + DACONTROL);

	/* write data */
	outw(data[0], devpriv->dac + DADATA + channel * 2);

	/* return the number of samples read/written */
	return 1;
}

// lowlevel read from eeprom
static unsigned int cb_pcidda_serial_in(comedi_device *dev)
{
	unsigned int value = 0;
	int i;
	const int value_width = 16;	// number of bits wide values are

	for(i = 1; i <= value_width; i++)
	{
		// read bits most significant bit first
		if(inw_p(devpriv->dac + DACALIBRATION1) & SERIAL_OUT_BIT)
		{
			value |= 1 << (value_width - i);
		}
	}

	return value;
}

// lowlevel write to eeprom/dac
static void cb_pcidda_serial_out(comedi_device *dev, unsigned int value, unsigned int num_bits)
{
	int i;

	for(i = 1; i <= num_bits; i++)
	{
		// send bits most significant bit first
		if(value & (1 << (num_bits - i)))
			devpriv->dac_cal1_bits |= SERIAL_IN_BIT;
		else
			devpriv->dac_cal1_bits &= ~SERIAL_IN_BIT;
		outw_p(devpriv->dac_cal1_bits, devpriv->dac + DACALIBRATION1);
	}
}


// reads a 16 bit value from board's eeprom
static unsigned int cb_pcidda_read_eeprom(comedi_device *dev, unsigned int address)
{
	unsigned int i;
	unsigned int cal2_bits;
	unsigned int value;
	const int max_num_caldacs = 4;	// one caldac for every two dac channels
	const int read_instruction = 0x6;	// bits to send to tell eeprom we want to read
	const int instruction_length = 3;
	const int address_length = 8;

	// send serial output stream to eeprom
	cal2_bits = SELECT_EEPROM_BIT | DESELECT_REF_DAC_BIT;
	// deactivate caldacs (one caldac for every two channels)
	for(i = 0; i < max_num_caldacs; i++)
	{
		cal2_bits |= DESELECT_CALDAC_BIT(i);
	}
	outw_p(cal2_bits, devpriv->dac + DACALIBRATION2);

	// tell eeprom we want to read
	cb_pcidda_serial_out(dev, read_instruction, instruction_length);
	// send address we want to read from
	cb_pcidda_serial_out(dev, address, address_length);

	value = cb_pcidda_serial_in(dev);

	// deactivate eeprom
	cal2_bits &= ~SELECT_EEPROM_BIT;
	outw_p(cal2_bits, devpriv->dac + DACALIBRATION2);

	return value;
}

// writes to 8 bit calibration dacs
static void cb_pcidda_write_caldac(comedi_device *dev, unsigned int caldac,
	unsigned int channel, unsigned int value)
{
	unsigned int cal2_bits;
	unsigned int i;
	const int num_channel_bits = 3;	// caldacs use 3 bit channel specification
	const int num_caldac_bits = 8;	// 8 bit calibration dacs
	const int max_num_caldacs = 4;	// one caldac for every two dac channels

	/* write 3 bit channel */
	cb_pcidda_serial_out(dev, channel, num_channel_bits);
	// write 8 bit caldac value
	cb_pcidda_serial_out(dev, value, num_caldac_bits);

	// latch stream into appropriate caldac
	// deselect reference dac
	cal2_bits = DESELECT_REF_DAC_BIT;
	// deactivate caldacs (one caldac for every two channels)
	for(i = 0; i < max_num_caldacs; i++)
	{
		cal2_bits |= DESELECT_CALDAC_BIT(i);
	}
	// activate the caldac we want
	cal2_bits &= ~DESELECT_CALDAC_BIT(caldac);
	outw_p(cal2_bits, devpriv->dac + DACALIBRATION2);
	// deactivate caldac
	cal2_bits |= DESELECT_CALDAC_BIT(caldac);
	outw_p(cal2_bits, devpriv->dac + DACALIBRATION2);
}

// returns caldac that calibrates given analog out channel
static unsigned int caldac_number(unsigned int channel)
{
	return channel / 2;
}

// returns caldac channel that provides fine gain for given ao channel
static unsigned int fine_gain_channel(unsigned int ao_channel)
{
	return 4 * (ao_channel % 2);
}
// returns caldac channel that provides coarse gain for given ao channel
static unsigned int coarse_gain_channel(unsigned int ao_channel)
{
	return 1 + 4 * (ao_channel % 2);
}

// returns caldac channel that provides coarse offset for given ao channel
static unsigned int coarse_offset_channel(unsigned int ao_channel)
{
	return 2 + 4 * (ao_channel % 2);
}

// returns caldac channel that provides fine offset for given ao channel
static unsigned int fine_offset_channel(unsigned int ao_channel)
{
	return 3 + 4 * (ao_channel % 2);
}

// returns eeprom address that provides offset for given ao channel and range
static unsigned int offset_eeprom_address(unsigned int ao_channel, unsigned int range)
{
	return 0x7 + 2 * range + 12 * ao_channel;
}

// returns eeprom address that provides gain calibration for given ao channel and range
static unsigned int gain_eeprom_address(unsigned int ao_channel, unsigned int range)
{
	return 0x8 + 2 * range + 12 * ao_channel;
}

// returns upper byte of eeprom entry, which gives the coarse adjustment values
static unsigned int eeprom_coarse_byte(unsigned int word)
{
	return (word >> 8) & 0xff;
}

// returns lower byte of eeprom entry, which gives the fine adjustment values
static unsigned int eeprom_fine_byte(unsigned int word)
{
	return word & 0xff;
}

// set caldacs to eeprom values for given channel and range
static void cb_pcidda_calibrate(comedi_device *dev, unsigned int channel, unsigned int range)
{
	unsigned int coarse_offset, fine_offset, coarse_gain, fine_gain;

	// remember range so we can tell when we need to readjust calibration
	devpriv->ao_range[channel] = range;

	// get values from eeprom data
	coarse_offset = eeprom_coarse_byte(devpriv->eeprom_data[offset_eeprom_address(channel, range)]);
	fine_offset = eeprom_fine_byte(devpriv->eeprom_data[offset_eeprom_address(channel, range)]);
	coarse_gain = eeprom_coarse_byte(devpriv->eeprom_data[gain_eeprom_address(channel, range)]);
	fine_gain = eeprom_fine_byte(devpriv->eeprom_data[gain_eeprom_address(channel, range)]);

	// set caldacs
	cb_pcidda_write_caldac(dev, caldac_number(channel), coarse_offset_channel(channel), coarse_offset);
	cb_pcidda_write_caldac(dev, caldac_number(channel), fine_offset_channel(channel), fine_offset);
	cb_pcidda_write_caldac(dev, caldac_number(channel), coarse_gain_channel(channel), coarse_gain);
	cb_pcidda_write_caldac(dev, caldac_number(channel), fine_gain_channel(channel), fine_gain);
}

/*
 * A convenient macro that defines init_module() and cleanup_module(),
 * as necessary.
 */
COMEDI_INITCLEANUP(driver_cb_pcidda);