Staging: comedi: fix read past end of array in cb_pcidda_attach()

[net-next-2.6.git] / drivers / staging / comedi / drivers / cb_pcidda.c

/*
    comedi/drivers/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@users.sourceforge.net>

    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
Description: 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 success/failure with other different cards to
<comedi@comedi.org>.
*/

#include "../comedidev.h"

#include "comedi_pci.h"
#include "8255.h"

#define PCI_VENDOR_ID_CB	0x1307	/*  PCI vendor number of ComputerBoards */
#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 const struct 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.
 */
struct cb_pcidda_board {
	const 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;
	const struct comedi_lrange *ranges;
};

static const struct 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 DEFINE_PCI_DEVICE_TABLE(cb_pcidda_pci_table) = {
	{
	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 ((const struct 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 struct comedi_device struct.  */
struct cb_pcidda_private {
	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 */
};

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

static int cb_pcidda_attach(struct comedi_device *dev,
			    struct comedi_devconfig *it);
static int cb_pcidda_detach(struct comedi_device *dev);
/* static int cb_pcidda_ai_rinsn(struct comedi_device *dev,struct comedi_subdevice *s,struct comedi_insn *insn,unsigned int *data); */
static int cb_pcidda_ao_winsn(struct comedi_device *dev,
			      struct comedi_subdevice *s,
			      struct comedi_insn *insn, unsigned int *data);

/* static int cb_pcidda_ai_cmd(struct comedi_device *dev, struct *comedi_subdevice *s);*/
/* static int cb_pcidda_ai_cmdtest(struct comedi_device *dev, struct comedi_subdevice *s, struct comedi_cmd *cmd); */
/* static int cb_pcidda_ns_to_timer(unsigned int *ns,int *round); */

static unsigned int cb_pcidda_serial_in(struct comedi_device *dev);
static void cb_pcidda_serial_out(struct comedi_device *dev, unsigned int value,
				 unsigned int num_bits);
static unsigned int cb_pcidda_read_eeprom(struct comedi_device *dev,
					  unsigned int address);
static void cb_pcidda_calibrate(struct comedi_device *dev, unsigned int channel,
				unsigned int range);

/*
 * The struct 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 struct 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(struct comedi_device *dev,
			    struct comedi_devconfig *it)
{
	struct comedi_subdevice *s;
	struct pci_dev *pcidev;
	int index;

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

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

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

	for (pcidev = pci_get_device(PCI_ANY_ID, PCI_ANY_ID, NULL);
	     pcidev != NULL;
	     pcidev = pci_get_device(PCI_ANY_ID, PCI_ANY_ID, 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]) {
					continue;
				}
			}
			for (index = 0; index < ARRAY_SIZE(cb_pcidda_boards); index++) {
				if (cb_pcidda_boards[index].device_id ==
				    pcidev->device) {
					goto found;
				}
			}
		}
	}
	if (!pcidev) {
		printk
		    ("Not a 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);

	/*
	 * Enable PCI device and request regions.
	 */
	if (comedi_pci_enable(pcidev, thisboard->name)) {
		printk
		    ("cb_pcidda: failed to enable PCI device and request regions\n");
		return -EIO;
	}

/*
 * Allocate the I/O ports.
 */
	devpriv->digitalio =
	    pci_resource_start(devpriv->pci_dev, DIGITALIO_BADRINDEX);
	devpriv->dac = pci_resource_start(devpriv->pci_dev, DAC_BADRINDEX);

/*
 * 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.
 */
	if (alloc_subdevices(dev, 3) < 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->subdev_flags |= SDF_CMD_READ; */
	/* 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, devpriv->digitalio);
	s = dev->subdevices + 2;
	subdev_8255_init(dev, s, NULL, 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(struct comedi_device *dev)
{
/*
 * Deallocate the I/O ports.
 */
	if (devpriv) {
		if (devpriv->pci_dev) {
			if (devpriv->dac)
				comedi_pci_disable(devpriv->pci_dev);
			pci_dev_put(devpriv->pci_dev);
		}
	}
	/*  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... ;-)
 */
#if 0
static int cb_pcidda_ai_cmd(struct comedi_device *dev,
			    struct 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);
}
#endif

#if 0
static int cb_pcidda_ai_cmdtest(struct comedi_device *dev,
				struct comedi_subdevice *s,
				struct 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 compatibility 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;
}
#endif

/* 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. */
#if 0
static int cb_pcidda_ns_to_timer(unsigned int *ns, int round)
{
	/* trivial timer */
	return *ns;
}
#endif

static int cb_pcidda_ao_winsn(struct comedi_device *dev,
			      struct comedi_subdevice *s,
			      struct comedi_insn *insn, unsigned int *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(struct 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(struct 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(struct 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 | DUMMY_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(struct 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 | DUMMY_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(struct 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_PCI_INITCLEANUP(driver_cb_pcidda, cb_pcidda_pci_table);