drivers/staging/comedi/drivers/cb_pcimdda.c - kernel/skids - Git at Google

 /*
     comedi/drivers/cb_pcimdda.c
     Computer Boards PCIM-DDA06-16 Comedi driver
     Author: Calin Culianu <calin@ajvar.org>

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

     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_pcimdda
 Description: Measurement Computing PCIM-DDA06-16
 Devices: [Measurement Computing] PCIM-DDA06-16 (cb_pcimdda)
 Author: Calin Culianu <calin@ajvar.org>
 Updated: Mon, 14 Apr 2008 15:15:51 +0100
 Status: works

 All features of the PCIM-DDA06-16 board are supported.  This board
 has 6 16-bit AO channels, and the usual 8255 DIO setup.  (24 channels,
 configurable in banks of 8 and 4, etc.).  This board does not support commands.

 The board has a peculiar way of specifying AO gain/range settings -- You have
 1 jumper bank on the card, which either makes all 6 AO channels either
 5 Volt unipolar, 5V bipolar, 10 Volt unipolar or 10V bipolar.

 Since there is absolutely _no_ way to tell in software how this jumper is set
 (well, at least according  to the rather thin spec. from Measurement Computing
  that comes with the board), the driver assumes the jumper is at its factory
 default setting of +/-5V.

 Also of note is the fact that this board features another jumper, whose
 state is also completely invisible to software.  It toggles two possible AO
 output modes on the board:

   - Update Mode: Writing to an AO channel instantaneously updates the actual
     signal output by the DAC on the board (this is the factory default).
   - Simultaneous XFER Mode: Writing to an AO channel has no effect until
     you read from any one of the AO channels.  This is useful for loading
     all 6 AO values, and then reading from any one of the AO channels on the
     device to instantly update all 6 AO values in unison.  Useful for some
     control apps, I would assume?  If your jumper is in this setting, then you
     need to issue your comedi_data_write()s to load all the values you want,
     then issue one comedi_data_read() on any channel on the AO subdevice
     to initiate the simultaneous XFER.

 Configuration Options:
   [0] PCI bus (optional)
   [1] PCI slot (optional)
   [2] analog output range jumper setting
       0 == +/- 5 V
       1 == +/- 10 V
 */

 /*
     This is a driver for the Computer Boards PCIM-DDA06-16 Analog Output
     card.  This board has a unique register layout and as such probably
     deserves its own driver file.

     It is theoretically possible to integrate this board into the cb_pcidda
     file, but since that isn't my code, I didn't want to significantly
     modify that file to support this board (I thought it impolite to do so).

     At any rate, if you feel ambitious, please feel free to take
     the code out of this file and combine it with a more unified driver
     file.

     I would like to thank Timothy Curry <Timothy.Curry@rdec.redstone.army.mil>
     for lending me a board so that I could write this driver.

     -Calin Culianu <calin@ajvar.org>
  */

 #include "../comedidev.h"

 #include "comedi_pci.h"

 #include "8255.h"

 /* device ids of the cards we support -- currently only 1 card supported */
 #define PCI_VENDOR_ID_COMPUTERBOARDS	0x1307
 #define PCI_ID_PCIM_DDA06_16		0x0053

 /*
  * This is straight from skel.c -- I did this in case this source file
  * will someday support more than 1 board...
  */
 struct board_struct {
 	const char *name;
 	unsigned short device_id;
 	int ao_chans;
 	int ao_bits;
 	int dio_chans;
 	int dio_method;
 	int dio_offset;		/* how many bytes into the BADR are the DIO ports */
 	int regs_badrindex;	/* IO Region for the control, analog output,
 				   and DIO registers */
 	int reg_sz;		/* number of bytes of registers in io region */
 };

 enum DIO_METHODS {
 	DIO_NONE = 0,
 	DIO_8255,
 	DIO_INTERNAL		/* unimplemented */
 };

 static const struct board_struct boards[] = {
 	{
 	 .name = "cb_pcimdda06-16",
 	 .device_id = PCI_ID_PCIM_DDA06_16,
 	 .ao_chans = 6,
 	 .ao_bits = 16,
 	 .dio_chans = 24,
 	 .dio_method = DIO_8255,
 	 .dio_offset = 12,
 	 .regs_badrindex = 3,
 	 .reg_sz = 16,
 	 }
 };

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

 #define REG_SZ (thisboard->reg_sz)
 #define REGS_BADRINDEX (thisboard->regs_badrindex)

 /* This is used by modprobe to translate PCI IDs to drivers.  Should
  * only be used for PCI and ISA-PnP devices */
 /* Please add your PCI vendor ID to comedidev.h, and it will be forwarded
  * upstream. */
 static DEFINE_PCI_DEVICE_TABLE(pci_table) = {
 	{
 	PCI_VENDOR_ID_COMPUTERBOARDS, PCI_ID_PCIM_DDA06_16, PCI_ANY_ID,
 		    PCI_ANY_ID, 0, 0, 0}, {
 	0}
 };

 MODULE_DEVICE_TABLE(pci, pci_table);

 /* 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 board_private_struct {
 	unsigned long registers;	/* set by probe */
 	unsigned long dio_registers;
 	char attached_to_8255;	/* boolean */
 	char attached_successfully;	/* boolean */
 	/* would be useful for a PCI device */
 	struct pci_dev *pci_dev;

 #define MAX_AO_READBACK_CHANNELS 6
 	/* Used for AO readback */
 	unsigned int ao_readback[MAX_AO_READBACK_CHANNELS];

 };

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

 /*
  * 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 int attach(struct comedi_device *dev, struct comedi_devconfig *it);
 static int detach(struct comedi_device *dev);
 static struct comedi_driver cb_pcimdda_driver = {
 	.driver_name = "cb_pcimdda",
 	.module = THIS_MODULE,
 	.attach = attach,
 	.detach = detach,
 };

 MODULE_AUTHOR("Calin A. Culianu <calin@rtlab.org>");
 MODULE_DESCRIPTION("Comedi low-level driver for the Computerboards PCIM-DDA "
 		   "series.  Currently only supports PCIM-DDA06-16 (which "
 		   "also happens to be the only board in this series. :) ) ");
 MODULE_LICENSE("GPL");
 COMEDI_PCI_INITCLEANUP_NOMODULE(cb_pcimdda_driver, pci_table);

 static int ao_winsn(struct comedi_device *dev, struct comedi_subdevice *s,
 		    struct comedi_insn *insn, unsigned int *data);
 static int ao_rinsn(struct comedi_device *dev, struct comedi_subdevice *s,
 		    struct comedi_insn *insn, unsigned int *data);

 /*---------------------------------------------------------------------------
   HELPER FUNCTION DECLARATIONS
 -----------------------------------------------------------------------------*/

 /* returns a maxdata value for a given n_bits */
 static inline unsigned int figure_out_maxdata(int bits)
 {
 	return ((unsigned int)1 << bits) - 1;
 }

 /*
  *  Probes for a supported device.
  *
  *  Prerequisite: private be allocated already inside dev
  *
  *  If the device is found, it returns 0 and has the following side effects:
  *
  *  o  assigns a struct pci_dev * to dev->private->pci_dev
  *  o  assigns a struct board * to dev->board_ptr
  *  o  sets dev->private->registers
  *  o  sets dev->private->dio_registers
  *
  *  Otherwise, returns a -errno on error
  */
 static int probe(struct comedi_device *dev, const struct comedi_devconfig *it);

 /*---------------------------------------------------------------------------
   FUNCTION DEFINITIONS
 -----------------------------------------------------------------------------*/

 /*
  * Attach is called by the Comedi core to configure the driver
  * for a particular board.  If you specified a board_name array
  * in the driver structure, dev->board_ptr contains that
  * address.
  */
 static int attach(struct comedi_device *dev, struct comedi_devconfig *it)
 {
 	struct comedi_subdevice *s;
 	int err;

 /*
  * Allocate the private structure area.  alloc_private() is a
  * convenient macro defined in comedidev.h.
  * if this function fails (returns negative) then the private area is
  * kfree'd by comedi
  */
 	if (alloc_private(dev, sizeof(struct board_private_struct)) < 0)
 		return -ENOMEM;

 /*
  * If you can probe the device to determine what device in a series
  * it is, this is the place to do it.  Otherwise, dev->board_ptr
  * should already be initialized.
  */
 	err = probe(dev, it);
 	if (err)
 		return err;

 /* Output some info */
 	printk("comedi%d: %s: ", dev->minor, thisboard->name);

 /*
  * Initialize dev->board_name.  Note that we can use the "thisboard"
  * macro now, since we just initialized it in the last line.
  */
 	dev->board_name = thisboard->name;

 /*
  * Allocate the subdevice structures.  alloc_subdevice() is a
  * convenient macro defined in comedidev.h.
  */
 	if (alloc_subdevices(dev, 2) < 0)
 		return -ENOMEM;

 	s = dev->subdevices + 0;

 	/* analog output subdevice */
 	s->type = COMEDI_SUBD_AO;
 	s->subdev_flags = SDF_WRITABLE | SDF_READABLE;
 	s->n_chan = thisboard->ao_chans;
 	s->maxdata = figure_out_maxdata(thisboard->ao_bits);
 	/* this is hard-coded here */
 	if (it->options[2])
 		s->range_table = &range_bipolar10;
 	else
 		s->range_table = &range_bipolar5;
 	s->insn_write = &ao_winsn;
 	s->insn_read = &ao_rinsn;

 	s = dev->subdevices + 1;
 	/* digital i/o subdevice */
 	if (thisboard->dio_chans) {
 		switch (thisboard->dio_method) {
 		case DIO_8255:
 			/* this is a straight 8255, so register us with the 8255 driver */
 			subdev_8255_init(dev, s, NULL, devpriv->dio_registers);
 			devpriv->attached_to_8255 = 1;
 			break;
 		case DIO_INTERNAL:
 		default:
 			printk("DIO_INTERNAL not implemented yet!\n");
 			return -ENXIO;
 			break;
 		}
 	} else {
 		s->type = COMEDI_SUBD_UNUSED;
 	}

 	devpriv->attached_successfully = 1;

 	printk("attached\n");

 	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 detach(struct comedi_device *dev)
 {
 	if (devpriv) {

 		if (dev->subdevices && devpriv->attached_to_8255) {
 			/* de-register us from the 8255 driver */
 			subdev_8255_cleanup(dev, dev->subdevices + 2);
 			devpriv->attached_to_8255 = 0;
 		}

 		if (devpriv->pci_dev) {
 			if (devpriv->registers)
 				comedi_pci_disable(devpriv->pci_dev);
 			pci_dev_put(devpriv->pci_dev);
 		}

 		if (devpriv->attached_successfully && thisboard)
 			printk("comedi%d: %s: detached\n", dev->minor,
 			       thisboard->name);

 	}

 	return 0;
 }

 static int ao_winsn(struct comedi_device *dev, struct comedi_subdevice *s,
 		    struct comedi_insn *insn, unsigned int *data)
 {
 	int i;
 	int chan = CR_CHAN(insn->chanspec);
 	unsigned long offset = devpriv->registers + chan * 2;

 	/* Writing a list of values to an AO channel is probably not
 	 * very useful, but that's how the interface is defined. */
 	for (i = 0; i < insn->n; i++) {
 		/*  first, load the low byte */
 		outb((char)(data[i] & 0x00ff), offset);
 		/*  next, write the high byte -- only after this is written is
 		   the channel voltage updated in the DAC, unless
 		   we're in simultaneous xfer mode (jumper on card)
 		   then a rinsn is necessary to actually update the DAC --
 		   see ao_rinsn() below... */
 		outb((char)(data[i] >> 8 & 0x00ff), offset + 1);

 		/* for testing only.. the actual rinsn SHOULD do an inw!
 		   (see the stuff about simultaneous XFER mode on this board) */
 		devpriv->ao_readback[chan] = data[i];
 	}

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

 /* AO subdevices should have a read insn as well as a write insn.

    Usually this means copying a value stored in devpriv->ao_readback.
    However, since this board has this jumper setting called "Simultaneous
    Xfer mode" (off by default), we will support it.  Simultaneaous xfer
    mode is accomplished by loading ALL the values you want for AO in all the
    channels, then READing off one of the AO registers to initiate the
    instantaneous simultaneous update of all DAC outputs, which makes
    all AO channels update simultaneously.  This is useful for some control
    applications, I would imagine.
 */
 static int ao_rinsn(struct comedi_device *dev, struct comedi_subdevice *s,
 		    struct comedi_insn *insn, unsigned int *data)
 {
 	int i;
 	int chan = CR_CHAN(insn->chanspec);

 	for (i = 0; i < insn->n; i++) {
 		inw(devpriv->registers + chan * 2);
 		/* should I set data[i] to the result of the actual read on the register
 		   or the cached unsigned int in devpriv->ao_readback[]? */
 		data[i] = devpriv->ao_readback[chan];
 	}

 	return i;
 }

 /*---------------------------------------------------------------------------
   HELPER FUNCTION DEFINITIONS
 -----------------------------------------------------------------------------*/

 /*
  *  Probes for a supported device.
  *
  *  Prerequisite: private be allocated already inside dev
  *
  *  If the device is found, it returns 0 and has the following side effects:
  *
  *  o  assigns a struct pci_dev * to dev->private->pci_dev
  *  o  assigns a struct board * to dev->board_ptr
  *  o  sets dev->private->registers
  *  o  sets dev->private->dio_registers
  *
  *  Otherwise, returns a -errno on error
  */
 static int probe(struct comedi_device *dev, const struct comedi_devconfig *it)
 {
 	struct pci_dev *pcidev;
 	int index;
 	unsigned long registers;

 	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)) {
 		/*  is it not a computer boards card? */
 		if (pcidev->vendor != PCI_VENDOR_ID_COMPUTERBOARDS)
 			continue;
 		/*  loop through cards supported by this driver */
 		for (index = 0; index < ARRAY_SIZE(boards); index++) {
 			if (boards[index].device_id != pcidev->device)
 				continue;
 			/*  was a particular bus/slot requested? */
 			if (it->options[0] || it->options[1]) {
 				/*  are we on the wrong bus/slot? */
 				if (pcidev->bus->number != it->options[0] ||
 				    PCI_SLOT(pcidev->devfn) != it->options[1]) {
 					continue;
 				}
 			}
 			/* found ! */

 			devpriv->pci_dev = pcidev;
 			dev->board_ptr = boards + index;
 			if (comedi_pci_enable(pcidev, thisboard->name)) {
 				printk
 				    ("cb_pcimdda: Failed to enable PCI device and request regions\n");
 				return -EIO;
 			}
 			registers =
 			    pci_resource_start(devpriv->pci_dev,
 					       REGS_BADRINDEX);
 			devpriv->registers = registers;
 			devpriv->dio_registers
 			    = devpriv->registers + thisboard->dio_offset;
 			return 0;
 		}
 	}

 	printk("cb_pcimdda: No supported ComputerBoards/MeasurementComputing "
 	       "card found at the requested position\n");
 	return -ENODEV;
 }
	/*
	comedi/drivers/cb_pcimdda.c
	Computer Boards PCIM-DDA06-16 Comedi driver
	Author: Calin Culianu <calin@ajvar.org>

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

	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_pcimdda
	Description: Measurement Computing PCIM-DDA06-16
	Devices: [Measurement Computing] PCIM-DDA06-16 (cb_pcimdda)
	Author: Calin Culianu <calin@ajvar.org>
	Updated: Mon, 14 Apr 2008 15:15:51 +0100
	Status: works

	All features of the PCIM-DDA06-16 board are supported. This board
	has 6 16-bit AO channels, and the usual 8255 DIO setup. (24 channels,
	configurable in banks of 8 and 4, etc.). This board does not support commands.

	The board has a peculiar way of specifying AO gain/range settings -- You have
	1 jumper bank on the card, which either makes all 6 AO channels either
	5 Volt unipolar, 5V bipolar, 10 Volt unipolar or 10V bipolar.

	Since there is absolutely _no_ way to tell in software how this jumper is set
	(well, at least according to the rather thin spec. from Measurement Computing
	that comes with the board), the driver assumes the jumper is at its factory
	default setting of +/-5V.

	Also of note is the fact that this board features another jumper, whose
	state is also completely invisible to software. It toggles two possible AO
	output modes on the board:

	- Update Mode: Writing to an AO channel instantaneously updates the actual
	signal output by the DAC on the board (this is the factory default).
	- Simultaneous XFER Mode: Writing to an AO channel has no effect until
	you read from any one of the AO channels. This is useful for loading
	all 6 AO values, and then reading from any one of the AO channels on the
	device to instantly update all 6 AO values in unison. Useful for some
	control apps, I would assume? If your jumper is in this setting, then you
	need to issue your comedi_data_write()s to load all the values you want,
	then issue one comedi_data_read() on any channel on the AO subdevice
	to initiate the simultaneous XFER.

	Configuration Options:
	[0] PCI bus (optional)
	[1] PCI slot (optional)
	[2] analog output range jumper setting
	0 == +/- 5 V
	1 == +/- 10 V
	*/

	/*
	This is a driver for the Computer Boards PCIM-DDA06-16 Analog Output
	card. This board has a unique register layout and as such probably
	deserves its own driver file.

	It is theoretically possible to integrate this board into the cb_pcidda
	file, but since that isn't my code, I didn't want to significantly
	modify that file to support this board (I thought it impolite to do so).

	At any rate, if you feel ambitious, please feel free to take
	the code out of this file and combine it with a more unified driver
	file.

	I would like to thank Timothy Curry <Timothy.Curry@rdec.redstone.army.mil>
	for lending me a board so that I could write this driver.

	-Calin Culianu <calin@ajvar.org>
	*/

	#include "../comedidev.h"

	#include "comedi_pci.h"

	#include "8255.h"

	/* device ids of the cards we support -- currently only 1 card supported */
	#define PCI_VENDOR_ID_COMPUTERBOARDS 0x1307
	#define PCI_ID_PCIM_DDA06_16 0x0053

	/*
	* This is straight from skel.c -- I did this in case this source file
	* will someday support more than 1 board...
	*/
	struct board_struct {
	const char *name;
	unsigned short device_id;
	int ao_chans;
	int ao_bits;
	int dio_chans;
	int dio_method;
	int dio_offset; /* how many bytes into the BADR are the DIO ports */
	int regs_badrindex; /* IO Region for the control, analog output,
	and DIO registers */
	int reg_sz; /* number of bytes of registers in io region */
	};

	enum DIO_METHODS {
	DIO_NONE = 0,
	DIO_8255,
	DIO_INTERNAL /* unimplemented */
	};

	static const struct board_struct boards[] = {
	{
	.name = "cb_pcimdda06-16",
	.device_id = PCI_ID_PCIM_DDA06_16,
	.ao_chans = 6,
	.ao_bits = 16,
	.dio_chans = 24,
	.dio_method = DIO_8255,
	.dio_offset = 12,
	.regs_badrindex = 3,
	.reg_sz = 16,
	}
	};

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

	#define REG_SZ (thisboard->reg_sz)
	#define REGS_BADRINDEX (thisboard->regs_badrindex)

	/* This is used by modprobe to translate PCI IDs to drivers. Should
	* only be used for PCI and ISA-PnP devices */
	/* Please add your PCI vendor ID to comedidev.h, and it will be forwarded
	* upstream. */
	static DEFINE_PCI_DEVICE_TABLE(pci_table) = {
	{
	PCI_VENDOR_ID_COMPUTERBOARDS, PCI_ID_PCIM_DDA06_16, PCI_ANY_ID,
	PCI_ANY_ID, 0, 0, 0}, {
	0}
	};

	MODULE_DEVICE_TABLE(pci, pci_table);

	/* 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 board_private_struct {
	unsigned long registers; /* set by probe */
	unsigned long dio_registers;
	char attached_to_8255; /* boolean */
	char attached_successfully; /* boolean */
	/* would be useful for a PCI device */
	struct pci_dev *pci_dev;

	#define MAX_AO_READBACK_CHANNELS 6
	/* Used for AO readback */
	unsigned int ao_readback[MAX_AO_READBACK_CHANNELS];

	};

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

	/*
	* 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 int attach(struct comedi_device dev, struct comedi_devconfig it);
	static int detach(struct comedi_device *dev);
	static struct comedi_driver cb_pcimdda_driver = {
	.driver_name = "cb_pcimdda",
	.module = THIS_MODULE,
	.attach = attach,
	.detach = detach,
	};

	MODULE_AUTHOR("Calin A. Culianu <calin@rtlab.org>");
	MODULE_DESCRIPTION("Comedi low-level driver for the Computerboards PCIM-DDA "
	"series. Currently only supports PCIM-DDA06-16 (which "
	"also happens to be the only board in this series. :) ) ");
	MODULE_LICENSE("GPL");
	COMEDI_PCI_INITCLEANUP_NOMODULE(cb_pcimdda_driver, pci_table);

	static int ao_winsn(struct comedi_device dev, struct comedi_subdevice s,
	struct comedi_insn insn, unsigned int data);
	static int ao_rinsn(struct comedi_device dev, struct comedi_subdevice s,
	struct comedi_insn insn, unsigned int data);

	/*---------------------------------------------------------------------------
	HELPER FUNCTION DECLARATIONS
	-----------------------------------------------------------------------------*/

	/* returns a maxdata value for a given n_bits */
	static inline unsigned int figure_out_maxdata(int bits)
	{
	return ((unsigned int)1 << bits) - 1;
	}

	/*
	* Probes for a supported device.
	*
	* Prerequisite: private be allocated already inside dev
	*
	* If the device is found, it returns 0 and has the following side effects:
	*
	* o assigns a struct pci_dev * to dev->private->pci_dev
	* o assigns a struct board * to dev->board_ptr
	* o sets dev->private->registers
	* o sets dev->private->dio_registers
	*
	* Otherwise, returns a -errno on error
	*/
	static int probe(struct comedi_device dev, const struct comedi_devconfig it);

	/*---------------------------------------------------------------------------
	FUNCTION DEFINITIONS
	-----------------------------------------------------------------------------*/

	/*
	* Attach is called by the Comedi core to configure the driver
	* for a particular board. If you specified a board_name array
	* in the driver structure, dev->board_ptr contains that
	* address.
	*/
	static int attach(struct comedi_device dev, struct comedi_devconfig it)
	{
	struct comedi_subdevice *s;
	int err;

	/*
	* Allocate the private structure area. alloc_private() is a
	* convenient macro defined in comedidev.h.
	* if this function fails (returns negative) then the private area is
	* kfree'd by comedi
	*/
	if (alloc_private(dev, sizeof(struct board_private_struct)) < 0)
	return -ENOMEM;

	/*
	* If you can probe the device to determine what device in a series
	* it is, this is the place to do it. Otherwise, dev->board_ptr
	* should already be initialized.
	*/
	err = probe(dev, it);
	if (err)
	return err;

	/* Output some info */
	printk("comedi%d: %s: ", dev->minor, thisboard->name);

	/*
	* Initialize dev->board_name. Note that we can use the "thisboard"
	* macro now, since we just initialized it in the last line.
	*/
	dev->board_name = thisboard->name;

	/*
	* Allocate the subdevice structures. alloc_subdevice() is a
	* convenient macro defined in comedidev.h.
	*/
	if (alloc_subdevices(dev, 2) < 0)
	return -ENOMEM;

	s = dev->subdevices + 0;

	/* analog output subdevice */
	s->type = COMEDI_SUBD_AO;
	s->subdev_flags = SDF_WRITABLE \| SDF_READABLE;
	s->n_chan = thisboard->ao_chans;
	s->maxdata = figure_out_maxdata(thisboard->ao_bits);
	/* this is hard-coded here */
	if (it->options[2])
	s->range_table = &range_bipolar10;
	else
	s->range_table = &range_bipolar5;
	s->insn_write = &ao_winsn;
	s->insn_read = &ao_rinsn;

	s = dev->subdevices + 1;
	/* digital i/o subdevice */
	if (thisboard->dio_chans) {
	switch (thisboard->dio_method) {
	case DIO_8255:
	/* this is a straight 8255, so register us with the 8255 driver */
	subdev_8255_init(dev, s, NULL, devpriv->dio_registers);
	devpriv->attached_to_8255 = 1;
	break;
	case DIO_INTERNAL:
	default:
	printk("DIO_INTERNAL not implemented yet!\n");
	return -ENXIO;
	break;
	}
	} else {
	s->type = COMEDI_SUBD_UNUSED;
	}

	devpriv->attached_successfully = 1;

	printk("attached\n");

	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 detach(struct comedi_device *dev)
	{
	if (devpriv) {

	if (dev->subdevices && devpriv->attached_to_8255) {
	/* de-register us from the 8255 driver */
	subdev_8255_cleanup(dev, dev->subdevices + 2);
	devpriv->attached_to_8255 = 0;
	}

	if (devpriv->pci_dev) {
	if (devpriv->registers)
	comedi_pci_disable(devpriv->pci_dev);
	pci_dev_put(devpriv->pci_dev);
	}

	if (devpriv->attached_successfully && thisboard)
	printk("comedi%d: %s: detached\n", dev->minor,
	thisboard->name);

	}

	return 0;
	}

	static int ao_winsn(struct comedi_device dev, struct comedi_subdevice s,
	struct comedi_insn insn, unsigned int data)
	{
	int i;
	int chan = CR_CHAN(insn->chanspec);
	unsigned long offset = devpriv->registers + chan * 2;

	/* Writing a list of values to an AO channel is probably not
	* very useful, but that's how the interface is defined. */
	for (i = 0; i < insn->n; i++) {
	/* first, load the low byte */
	outb((char)(data[i] & 0x00ff), offset);
	/* next, write the high byte -- only after this is written is
	the channel voltage updated in the DAC, unless
	we're in simultaneous xfer mode (jumper on card)
	then a rinsn is necessary to actually update the DAC --
	see ao_rinsn() below... */
	outb((char)(data[i] >> 8 & 0x00ff), offset + 1);

	/* for testing only.. the actual rinsn SHOULD do an inw!
	(see the stuff about simultaneous XFER mode on this board) */
	devpriv->ao_readback[chan] = data[i];
	}

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

	/* AO subdevices should have a read insn as well as a write insn.

	Usually this means copying a value stored in devpriv->ao_readback.
	However, since this board has this jumper setting called "Simultaneous
	Xfer mode" (off by default), we will support it. Simultaneaous xfer
	mode is accomplished by loading ALL the values you want for AO in all the
	channels, then READing off one of the AO registers to initiate the
	instantaneous simultaneous update of all DAC outputs, which makes
	all AO channels update simultaneously. This is useful for some control
	applications, I would imagine.
	*/
	static int ao_rinsn(struct comedi_device dev, struct comedi_subdevice s,
	struct comedi_insn insn, unsigned int data)
	{
	int i;
	int chan = CR_CHAN(insn->chanspec);

	for (i = 0; i < insn->n; i++) {
	inw(devpriv->registers + chan * 2);
	/* should I set data[i] to the result of the actual read on the register
	or the cached unsigned int in devpriv->ao_readback[]? */
	data[i] = devpriv->ao_readback[chan];
	}

	return i;
	}

	/*---------------------------------------------------------------------------
	HELPER FUNCTION DEFINITIONS
	-----------------------------------------------------------------------------*/

	/*
	* Probes for a supported device.
	*
	* Prerequisite: private be allocated already inside dev
	*
	* If the device is found, it returns 0 and has the following side effects:
	*
	* o assigns a struct pci_dev * to dev->private->pci_dev
	* o assigns a struct board * to dev->board_ptr
	* o sets dev->private->registers
	* o sets dev->private->dio_registers
	*
	* Otherwise, returns a -errno on error
	*/
	static int probe(struct comedi_device dev, const struct comedi_devconfig it)
	{
	struct pci_dev *pcidev;
	int index;
	unsigned long registers;

	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)) {
	/* is it not a computer boards card? */
	if (pcidev->vendor != PCI_VENDOR_ID_COMPUTERBOARDS)
	continue;
	/* loop through cards supported by this driver */
	for (index = 0; index < ARRAY_SIZE(boards); index++) {
	if (boards[index].device_id != pcidev->device)
	continue;
	/* was a particular bus/slot requested? */
	if (it->options[0] \|\| it->options[1]) {
	/* are we on the wrong bus/slot? */
	if (pcidev->bus->number != it->options[0] \|\|
	PCI_SLOT(pcidev->devfn) != it->options[1]) {
	continue;
	}
	}
	/* found ! */

	devpriv->pci_dev = pcidev;
	dev->board_ptr = boards + index;
	if (comedi_pci_enable(pcidev, thisboard->name)) {
	printk
	("cb_pcimdda: Failed to enable PCI device and request regions\n");
	return -EIO;
	}
	registers =
	pci_resource_start(devpriv->pci_dev,
	REGS_BADRINDEX);
	devpriv->registers = registers;
	devpriv->dio_registers
	= devpriv->registers + thisboard->dio_offset;
	return 0;
	}
	}

	printk("cb_pcimdda: No supported ComputerBoards/MeasurementComputing "
	"card found at the requested position\n");
	return -ENODEV;
	}