drivers/staging/comedi/drivers.c - linux/kernel/git/bpf/bpf-next - Git at Google

 /*
     module/drivers.c
     functions for manipulating drivers

     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.

     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.

 */

 #include <linux/device.h>
 #include <linux/module.h>
 #include <linux/errno.h>
 #include <linux/kconfig.h>
 #include <linux/kernel.h>
 #include <linux/sched.h>
 #include <linux/fcntl.h>
 #include <linux/delay.h>
 #include <linux/ioport.h>
 #include <linux/mm.h>
 #include <linux/slab.h>
 #include <linux/highmem.h>	/* for SuSE brokenness */
 #include <linux/vmalloc.h>
 #include <linux/cdev.h>
 #include <linux/dma-mapping.h>
 #include <linux/io.h>

 #include "comedidev.h"
 #include "comedi_internal.h"

 struct comedi_driver *comedi_drivers;

 int comedi_set_hw_dev(struct comedi_device *dev, struct device *hw_dev)
 {
 	if (hw_dev == dev->hw_dev)
 		return 0;
 	if (dev->hw_dev != NULL)
 		return -EEXIST;
 	dev->hw_dev = get_device(hw_dev);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(comedi_set_hw_dev);

 static void comedi_clear_hw_dev(struct comedi_device *dev)
 {
 	put_device(dev->hw_dev);
 	dev->hw_dev = NULL;
 }

 int comedi_alloc_subdevices(struct comedi_device *dev, int num_subdevices)
 {
 	struct comedi_subdevice *s;
 	int i;

 	if (num_subdevices < 1)
 		return -EINVAL;

 	s = kcalloc(num_subdevices, sizeof(*s), GFP_KERNEL);
 	if (!s)
 		return -ENOMEM;
 	dev->subdevices = s;
 	dev->n_subdevices = num_subdevices;

 	for (i = 0; i < num_subdevices; ++i) {
 		s = &dev->subdevices[i];
 		s->device = dev;
 		s->index = i;
 		s->async_dma_dir = DMA_NONE;
 		spin_lock_init(&s->spin_lock);
 		s->minor = -1;
 	}
 	return 0;
 }
 EXPORT_SYMBOL_GPL(comedi_alloc_subdevices);

 static void cleanup_device(struct comedi_device *dev)
 {
 	int i;
 	struct comedi_subdevice *s;

 	if (dev->subdevices) {
 		for (i = 0; i < dev->n_subdevices; i++) {
 			s = &dev->subdevices[i];
 			comedi_free_subdevice_minor(s);
 			if (s->async) {
 				comedi_buf_alloc(dev, s, 0);
 				kfree(s->async);
 			}
 		}
 		kfree(dev->subdevices);
 		dev->subdevices = NULL;
 		dev->n_subdevices = 0;
 	}
 	kfree(dev->private);
 	dev->private = NULL;
 	dev->driver = NULL;
 	dev->board_name = NULL;
 	dev->board_ptr = NULL;
 	dev->iobase = 0;
 	dev->irq = 0;
 	dev->read_subdev = NULL;
 	dev->write_subdev = NULL;
 	dev->open = NULL;
 	dev->close = NULL;
 	comedi_clear_hw_dev(dev);
 }

 static void __comedi_device_detach(struct comedi_device *dev)
 {
 	dev->attached = 0;
 	if (dev->driver)
 		dev->driver->detach(dev);
 	else
 		dev_warn(dev->class_dev,
 			 "BUG: dev->driver=NULL in comedi_device_detach()\n");
 	cleanup_device(dev);
 }

 void comedi_device_detach(struct comedi_device *dev)
 {
 	if (!dev->attached)
 		return;
 	__comedi_device_detach(dev);
 }

 static int poll_invalid(struct comedi_device *dev, struct comedi_subdevice *s)
 {
 	return -EINVAL;
 }

 int insn_inval(struct comedi_device *dev, struct comedi_subdevice *s,
 	       struct comedi_insn *insn, unsigned int *data)
 {
 	return -EINVAL;
 }

 static int insn_rw_emulate_bits(struct comedi_device *dev,
 				struct comedi_subdevice *s,
 				struct comedi_insn *insn, unsigned int *data)
 {
 	struct comedi_insn new_insn;
 	int ret;
 	static const unsigned channels_per_bitfield = 32;

 	unsigned chan = CR_CHAN(insn->chanspec);
 	const unsigned base_bitfield_channel =
 	    (chan < channels_per_bitfield) ? 0 : chan;
 	unsigned int new_data[2];
 	memset(new_data, 0, sizeof(new_data));
 	memset(&new_insn, 0, sizeof(new_insn));
 	new_insn.insn = INSN_BITS;
 	new_insn.chanspec = base_bitfield_channel;
 	new_insn.n = 2;
 	new_insn.subdev = insn->subdev;

 	if (insn->insn == INSN_WRITE) {
 		if (!(s->subdev_flags & SDF_WRITABLE))
 			return -EINVAL;
 		new_data[0] = 1 << (chan - base_bitfield_channel); /* mask */
 		new_data[1] = data[0] ? (1 << (chan - base_bitfield_channel))
 			      : 0; /* bits */
 	}

 	ret = s->insn_bits(dev, s, &new_insn, new_data);
 	if (ret < 0)
 		return ret;

 	if (insn->insn == INSN_READ)
 		data[0] = (new_data[1] >> (chan - base_bitfield_channel)) & 1;

 	return 1;
 }

 static int __comedi_device_postconfig_async(struct comedi_device *dev,
 					    struct comedi_subdevice *s)
 {
 	struct comedi_async *async;
 	unsigned int buf_size;
 	int ret;

 	if ((s->subdev_flags & (SDF_CMD_READ | SDF_CMD_WRITE)) == 0) {
 		dev_warn(dev->class_dev,
 			 "async subdevices must support SDF_CMD_READ or SDF_CMD_WRITE\n");
 		return -EINVAL;
 	}
 	if (!s->do_cmdtest) {
 		dev_warn(dev->class_dev,
 			 "async subdevices must have a do_cmdtest() function\n");
 		return -EINVAL;
 	}

 	async = kzalloc(sizeof(*async), GFP_KERNEL);
 	if (!async)
 		return -ENOMEM;

 	init_waitqueue_head(&async->wait_head);
 	async->subdevice = s;
 	s->async = async;

 	async->max_bufsize = comedi_default_buf_maxsize_kb * 1024;
 	buf_size = comedi_default_buf_size_kb * 1024;
 	if (buf_size > async->max_bufsize)
 		buf_size = async->max_bufsize;

 	if (comedi_buf_alloc(dev, s, buf_size) < 0) {
 		dev_warn(dev->class_dev, "Buffer allocation failed\n");
 		return -ENOMEM;
 	}
 	if (s->buf_change) {
 		ret = s->buf_change(dev, s, buf_size);
 		if (ret < 0)
 			return ret;
 	}

 	comedi_alloc_subdevice_minor(s);

 	return 0;
 }

 static int __comedi_device_postconfig(struct comedi_device *dev)
 {
 	struct comedi_subdevice *s;
 	int ret;
 	int i;

 	for (i = 0; i < dev->n_subdevices; i++) {
 		s = &dev->subdevices[i];

 		if (s->type == COMEDI_SUBD_UNUSED)
 			continue;

 		if (s->len_chanlist == 0)
 			s->len_chanlist = 1;

 		if (s->do_cmd) {
 			ret = __comedi_device_postconfig_async(dev, s);
 			if (ret)
 				return ret;
 		}

 		if (!s->range_table && !s->range_table_list)
 			s->range_table = &range_unknown;

 		if (!s->insn_read && s->insn_bits)
 			s->insn_read = insn_rw_emulate_bits;
 		if (!s->insn_write && s->insn_bits)
 			s->insn_write = insn_rw_emulate_bits;

 		if (!s->insn_read)
 			s->insn_read = insn_inval;
 		if (!s->insn_write)
 			s->insn_write = insn_inval;
 		if (!s->insn_bits)
 			s->insn_bits = insn_inval;
 		if (!s->insn_config)
 			s->insn_config = insn_inval;

 		if (!s->poll)
 			s->poll = poll_invalid;
 	}

 	return 0;
 }

 /* do a little post-config cleanup */
 /* called with module refcount incremented, decrements it */
 static int comedi_device_postconfig(struct comedi_device *dev)
 {
 	int ret = __comedi_device_postconfig(dev);
 	module_put(dev->driver->module);
 	if (ret < 0) {
 		__comedi_device_detach(dev);
 		return ret;
 	}
 	if (!dev->board_name) {
 		dev_warn(dev->class_dev, "BUG: dev->board_name=NULL\n");
 		dev->board_name = "BUG";
 	}
 	smp_wmb();
 	dev->attached = 1;
 	return 0;
 }

 /*
  * Generic recognize function for drivers that register their supported
  * board names.
  *
  * 'driv->board_name' points to a 'const char *' member within the
  * zeroth element of an array of some private board information
  * structure, say 'struct foo_board' containing a member 'const char
  * *board_name' that is initialized to point to a board name string that
  * is one of the candidates matched against this function's 'name'
  * parameter.
  *
  * 'driv->offset' is the size of the private board information
  * structure, say 'sizeof(struct foo_board)', and 'driv->num_names' is
  * the length of the array of private board information structures.
  *
  * If one of the board names in the array of private board information
  * structures matches the name supplied to this function, the function
  * returns a pointer to the pointer to the board name, otherwise it
  * returns NULL.  The return value ends up in the 'board_ptr' member of
  * a 'struct comedi_device' that the low-level comedi driver's
  * 'attach()' hook can convert to a point to a particular element of its
  * array of private board information structures by subtracting the
  * offset of the member that points to the board name.  (No subtraction
  * is required if the board name pointer is the first member of the
  * private board information structure, which is generally the case.)
  */
 static void *comedi_recognize(struct comedi_driver *driv, const char *name)
 {
 	char **name_ptr = (char **)driv->board_name;
 	int i;

 	for (i = 0; i < driv->num_names; i++) {
 		if (strcmp(*name_ptr, name) == 0)
 			return name_ptr;
 		name_ptr = (void *)name_ptr + driv->offset;
 	}

 	return NULL;
 }

 static void comedi_report_boards(struct comedi_driver *driv)
 {
 	unsigned int i;
 	const char *const *name_ptr;

 	pr_info("comedi: valid board names for %s driver are:\n",
 		driv->driver_name);

 	name_ptr = driv->board_name;
 	for (i = 0; i < driv->num_names; i++) {
 		pr_info(" %s\n", *name_ptr);
 		name_ptr = (const char **)((char *)name_ptr + driv->offset);
 	}

 	if (driv->num_names == 0)
 		pr_info(" %s\n", driv->driver_name);
 }

 int comedi_device_attach(struct comedi_device *dev, struct comedi_devconfig *it)
 {
 	struct comedi_driver *driv;
 	int ret;

 	if (dev->attached)
 		return -EBUSY;

 	for (driv = comedi_drivers; driv; driv = driv->next) {
 		if (!try_module_get(driv->module))
 			continue;
 		if (driv->num_names) {
 			dev->board_ptr = comedi_recognize(driv, it->board_name);
 			if (dev->board_ptr)
 				break;
 		} else if (strcmp(driv->driver_name, it->board_name) == 0)
 			break;
 		module_put(driv->module);
 	}
 	if (driv == NULL) {
 		/*  recognize has failed if we get here */
 		/*  report valid board names before returning error */
 		for (driv = comedi_drivers; driv; driv = driv->next) {
 			if (!try_module_get(driv->module))
 				continue;
 			comedi_report_boards(driv);
 			module_put(driv->module);
 		}
 		return -EIO;
 	}
 	if (driv->attach == NULL) {
 		/* driver does not support manual configuration */
 		dev_warn(dev->class_dev,
 			 "driver '%s' does not support attach using comedi_config\n",
 			 driv->driver_name);
 		module_put(driv->module);
 		return -ENOSYS;
 	}
 	/* initialize dev->driver here so
 	 * comedi_error() can be called from attach */
 	dev->driver = driv;
 	ret = driv->attach(dev, it);
 	if (ret < 0) {
 		module_put(dev->driver->module);
 		__comedi_device_detach(dev);
 		return ret;
 	}
 	return comedi_device_postconfig(dev);
 }

 int comedi_auto_config(struct device *hardware_device,
 		       struct comedi_driver *driver, unsigned long context)
 {
 	int minor;
 	struct comedi_device *comedi_dev;
 	int ret;

 	if (!driver->auto_attach) {
 		dev_warn(hardware_device,
 			 "BUG! comedi driver '%s' has no auto_attach handler\n",
 			 driver->driver_name);
 		return -EINVAL;
 	}

 	minor = comedi_alloc_board_minor(hardware_device);
 	if (minor < 0)
 		return minor;

 	comedi_dev = comedi_dev_from_minor(minor);

 	mutex_lock(&comedi_dev->mutex);
 	if (comedi_dev->attached)
 		ret = -EBUSY;
 	else if (!try_module_get(driver->module))
 		ret = -EIO;
 	else {
 		comedi_set_hw_dev(comedi_dev, hardware_device);
 		comedi_dev->driver = driver;
 		ret = driver->auto_attach(comedi_dev, context);
 		if (ret < 0) {
 			module_put(driver->module);
 			__comedi_device_detach(comedi_dev);
 		} else {
 			ret = comedi_device_postconfig(comedi_dev);
 		}
 	}
 	mutex_unlock(&comedi_dev->mutex);

 	if (ret < 0)
 		comedi_free_board_minor(minor);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(comedi_auto_config);

 void comedi_auto_unconfig(struct device *hardware_device)
 {
 	int minor;

 	if (hardware_device == NULL)
 		return;
 	minor = comedi_find_board_minor(hardware_device);
 	if (minor < 0)
 		return;
 	comedi_free_board_minor(minor);
 }
 EXPORT_SYMBOL_GPL(comedi_auto_unconfig);

 int comedi_driver_register(struct comedi_driver *driver)
 {
 	driver->next = comedi_drivers;
 	comedi_drivers = driver;

 	return 0;
 }
 EXPORT_SYMBOL(comedi_driver_register);

 int comedi_driver_unregister(struct comedi_driver *driver)
 {
 	struct comedi_driver *prev;
 	int i;

 	/* check for devices using this driver */
 	for (i = 0; i < COMEDI_NUM_BOARD_MINORS; i++) {
 		struct comedi_device *dev = comedi_dev_from_minor(i);

 		if (!dev)
 			continue;

 		mutex_lock(&dev->mutex);
 		if (dev->attached && dev->driver == driver) {
 			if (dev->use_count)
 				dev_warn(dev->class_dev,
 					 "BUG! detaching device with use_count=%d\n",
 					 dev->use_count);
 			comedi_device_detach(dev);
 		}
 		mutex_unlock(&dev->mutex);
 	}

 	if (comedi_drivers == driver) {
 		comedi_drivers = driver->next;
 		return 0;
 	}

 	for (prev = comedi_drivers; prev->next; prev = prev->next) {
 		if (prev->next == driver) {
 			prev->next = driver->next;
 			return 0;
 		}
 	}
 	return -EINVAL;
 }
 EXPORT_SYMBOL(comedi_driver_unregister);
	/*
	module/drivers.c
	functions for manipulating drivers

	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.

	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.

	*/

	#include <linux/device.h>
	#include <linux/module.h>
	#include <linux/errno.h>
	#include <linux/kconfig.h>
	#include <linux/kernel.h>
	#include <linux/sched.h>
	#include <linux/fcntl.h>
	#include <linux/delay.h>
	#include <linux/ioport.h>
	#include <linux/mm.h>
	#include <linux/slab.h>
	#include <linux/highmem.h> /* for SuSE brokenness */
	#include <linux/vmalloc.h>
	#include <linux/cdev.h>
	#include <linux/dma-mapping.h>
	#include <linux/io.h>

	#include "comedidev.h"
	#include "comedi_internal.h"

	struct comedi_driver *comedi_drivers;

	int comedi_set_hw_dev(struct comedi_device dev, struct device hw_dev)
	{
	if (hw_dev == dev->hw_dev)
	return 0;
	if (dev->hw_dev != NULL)
	return -EEXIST;
	dev->hw_dev = get_device(hw_dev);
	return 0;
	}
	EXPORT_SYMBOL_GPL(comedi_set_hw_dev);

	static void comedi_clear_hw_dev(struct comedi_device *dev)
	{
	put_device(dev->hw_dev);
	dev->hw_dev = NULL;
	}

	int comedi_alloc_subdevices(struct comedi_device *dev, int num_subdevices)
	{
	struct comedi_subdevice *s;
	int i;

	if (num_subdevices < 1)
	return -EINVAL;

	s = kcalloc(num_subdevices, sizeof(*s), GFP_KERNEL);
	if (!s)
	return -ENOMEM;
	dev->subdevices = s;
	dev->n_subdevices = num_subdevices;

	for (i = 0; i < num_subdevices; ++i) {
	s = &dev->subdevices[i];
	s->device = dev;
	s->index = i;
	s->async_dma_dir = DMA_NONE;
	spin_lock_init(&s->spin_lock);
	s->minor = -1;
	}
	return 0;
	}
	EXPORT_SYMBOL_GPL(comedi_alloc_subdevices);

	static void cleanup_device(struct comedi_device *dev)
	{
	int i;
	struct comedi_subdevice *s;

	if (dev->subdevices) {
	for (i = 0; i < dev->n_subdevices; i++) {
	s = &dev->subdevices[i];
	comedi_free_subdevice_minor(s);
	if (s->async) {
	comedi_buf_alloc(dev, s, 0);
	kfree(s->async);
	}
	}
	kfree(dev->subdevices);
	dev->subdevices = NULL;
	dev->n_subdevices = 0;
	}
	kfree(dev->private);
	dev->private = NULL;
	dev->driver = NULL;
	dev->board_name = NULL;
	dev->board_ptr = NULL;
	dev->iobase = 0;
	dev->irq = 0;
	dev->read_subdev = NULL;
	dev->write_subdev = NULL;
	dev->open = NULL;
	dev->close = NULL;
	comedi_clear_hw_dev(dev);
	}

	static void __comedi_device_detach(struct comedi_device *dev)
	{
	dev->attached = 0;
	if (dev->driver)
	dev->driver->detach(dev);
	else
	dev_warn(dev->class_dev,
	"BUG: dev->driver=NULL in comedi_device_detach()\n");
	cleanup_device(dev);
	}

	void comedi_device_detach(struct comedi_device *dev)
	{
	if (!dev->attached)
	return;
	__comedi_device_detach(dev);
	}

	static int poll_invalid(struct comedi_device dev, struct comedi_subdevice s)
	{
	return -EINVAL;
	}

	int insn_inval(struct comedi_device dev, struct comedi_subdevice s,
	struct comedi_insn insn, unsigned int data)
	{
	return -EINVAL;
	}

	static int insn_rw_emulate_bits(struct comedi_device *dev,
	struct comedi_subdevice *s,
	struct comedi_insn insn, unsigned int data)
	{
	struct comedi_insn new_insn;
	int ret;
	static const unsigned channels_per_bitfield = 32;

	unsigned chan = CR_CHAN(insn->chanspec);
	const unsigned base_bitfield_channel =
	(chan < channels_per_bitfield) ? 0 : chan;
	unsigned int new_data[2];
	memset(new_data, 0, sizeof(new_data));
	memset(&new_insn, 0, sizeof(new_insn));
	new_insn.insn = INSN_BITS;
	new_insn.chanspec = base_bitfield_channel;
	new_insn.n = 2;
	new_insn.subdev = insn->subdev;

	if (insn->insn == INSN_WRITE) {
	if (!(s->subdev_flags & SDF_WRITABLE))
	return -EINVAL;
	new_data[0] = 1 << (chan - base_bitfield_channel); /* mask */
	new_data[1] = data[0] ? (1 << (chan - base_bitfield_channel))
	: 0; /* bits */
	}

	ret = s->insn_bits(dev, s, &new_insn, new_data);
	if (ret < 0)
	return ret;

	if (insn->insn == INSN_READ)
	data[0] = (new_data[1] >> (chan - base_bitfield_channel)) & 1;

	return 1;
	}

	static int __comedi_device_postconfig_async(struct comedi_device *dev,
	struct comedi_subdevice *s)
	{
	struct comedi_async *async;
	unsigned int buf_size;
	int ret;

	if ((s->subdev_flags & (SDF_CMD_READ \| SDF_CMD_WRITE)) == 0) {
	dev_warn(dev->class_dev,
	"async subdevices must support SDF_CMD_READ or SDF_CMD_WRITE\n");
	return -EINVAL;
	}
	if (!s->do_cmdtest) {
	dev_warn(dev->class_dev,
	"async subdevices must have a do_cmdtest() function\n");
	return -EINVAL;
	}

	async = kzalloc(sizeof(*async), GFP_KERNEL);
	if (!async)
	return -ENOMEM;

	init_waitqueue_head(&async->wait_head);
	async->subdevice = s;
	s->async = async;

	async->max_bufsize = comedi_default_buf_maxsize_kb * 1024;
	buf_size = comedi_default_buf_size_kb * 1024;
	if (buf_size > async->max_bufsize)
	buf_size = async->max_bufsize;

	if (comedi_buf_alloc(dev, s, buf_size) < 0) {
	dev_warn(dev->class_dev, "Buffer allocation failed\n");
	return -ENOMEM;
	}
	if (s->buf_change) {
	ret = s->buf_change(dev, s, buf_size);
	if (ret < 0)
	return ret;
	}

	comedi_alloc_subdevice_minor(s);

	return 0;
	}

	static int __comedi_device_postconfig(struct comedi_device *dev)
	{
	struct comedi_subdevice *s;
	int ret;
	int i;

	for (i = 0; i < dev->n_subdevices; i++) {
	s = &dev->subdevices[i];

	if (s->type == COMEDI_SUBD_UNUSED)
	continue;

	if (s->len_chanlist == 0)
	s->len_chanlist = 1;

	if (s->do_cmd) {
	ret = __comedi_device_postconfig_async(dev, s);
	if (ret)
	return ret;
	}

	if (!s->range_table && !s->range_table_list)
	s->range_table = &range_unknown;

	if (!s->insn_read && s->insn_bits)
	s->insn_read = insn_rw_emulate_bits;
	if (!s->insn_write && s->insn_bits)
	s->insn_write = insn_rw_emulate_bits;

	if (!s->insn_read)
	s->insn_read = insn_inval;
	if (!s->insn_write)
	s->insn_write = insn_inval;
	if (!s->insn_bits)
	s->insn_bits = insn_inval;
	if (!s->insn_config)
	s->insn_config = insn_inval;

	if (!s->poll)
	s->poll = poll_invalid;
	}

	return 0;
	}

	/* do a little post-config cleanup */
	/* called with module refcount incremented, decrements it */
	static int comedi_device_postconfig(struct comedi_device *dev)
	{
	int ret = __comedi_device_postconfig(dev);
	module_put(dev->driver->module);
	if (ret < 0) {
	__comedi_device_detach(dev);
	return ret;
	}
	if (!dev->board_name) {
	dev_warn(dev->class_dev, "BUG: dev->board_name=NULL\n");
	dev->board_name = "BUG";
	}
	smp_wmb();
	dev->attached = 1;
	return 0;
	}

	/*
	* Generic recognize function for drivers that register their supported
	* board names.
	*
	* 'driv->board_name' points to a 'const char *' member within the
	* zeroth element of an array of some private board information
	* structure, say 'struct foo_board' containing a member 'const char
	* *board_name' that is initialized to point to a board name string that
	* is one of the candidates matched against this function's 'name'
	* parameter.
	*
	* 'driv->offset' is the size of the private board information
	* structure, say 'sizeof(struct foo_board)', and 'driv->num_names' is
	* the length of the array of private board information structures.
	*
	* If one of the board names in the array of private board information
	* structures matches the name supplied to this function, the function
	* returns a pointer to the pointer to the board name, otherwise it
	* returns NULL. The return value ends up in the 'board_ptr' member of
	* a 'struct comedi_device' that the low-level comedi driver's
	* 'attach()' hook can convert to a point to a particular element of its
	* array of private board information structures by subtracting the
	* offset of the member that points to the board name. (No subtraction
	* is required if the board name pointer is the first member of the
	* private board information structure, which is generally the case.)
	*/
	static void comedi_recognize(struct comedi_driver driv, const char *name)
	{
	char name_ptr = (char )driv->board_name;
	int i;

	for (i = 0; i < driv->num_names; i++) {
	if (strcmp(*name_ptr, name) == 0)
	return name_ptr;
	name_ptr = (void *)name_ptr + driv->offset;
	}

	return NULL;
	}

	static void comedi_report_boards(struct comedi_driver *driv)
	{
	unsigned int i;
	const char const name_ptr;

	pr_info("comedi: valid board names for %s driver are:\n",
	driv->driver_name);

	name_ptr = driv->board_name;
	for (i = 0; i < driv->num_names; i++) {
	pr_info(" %s\n", *name_ptr);
	name_ptr = (const char *)((char )name_ptr + driv->offset);
	}

	if (driv->num_names == 0)
	pr_info(" %s\n", driv->driver_name);
	}

	int comedi_device_attach(struct comedi_device dev, struct comedi_devconfig it)
	{
	struct comedi_driver *driv;
	int ret;

	if (dev->attached)
	return -EBUSY;

	for (driv = comedi_drivers; driv; driv = driv->next) {
	if (!try_module_get(driv->module))
	continue;
	if (driv->num_names) {
	dev->board_ptr = comedi_recognize(driv, it->board_name);
	if (dev->board_ptr)
	break;
	} else if (strcmp(driv->driver_name, it->board_name) == 0)
	break;
	module_put(driv->module);
	}
	if (driv == NULL) {
	/* recognize has failed if we get here */
	/* report valid board names before returning error */
	for (driv = comedi_drivers; driv; driv = driv->next) {
	if (!try_module_get(driv->module))
	continue;
	comedi_report_boards(driv);
	module_put(driv->module);
	}
	return -EIO;
	}
	if (driv->attach == NULL) {
	/* driver does not support manual configuration */
	dev_warn(dev->class_dev,
	"driver '%s' does not support attach using comedi_config\n",
	driv->driver_name);
	module_put(driv->module);
	return -ENOSYS;
	}
	/* initialize dev->driver here so
	* comedi_error() can be called from attach */
	dev->driver = driv;
	ret = driv->attach(dev, it);
	if (ret < 0) {
	module_put(dev->driver->module);
	__comedi_device_detach(dev);
	return ret;
	}
	return comedi_device_postconfig(dev);
	}

	int comedi_auto_config(struct device *hardware_device,
	struct comedi_driver *driver, unsigned long context)
	{
	int minor;
	struct comedi_device *comedi_dev;
	int ret;

	if (!driver->auto_attach) {
	dev_warn(hardware_device,
	"BUG! comedi driver '%s' has no auto_attach handler\n",
	driver->driver_name);
	return -EINVAL;
	}

	minor = comedi_alloc_board_minor(hardware_device);
	if (minor < 0)
	return minor;

	comedi_dev = comedi_dev_from_minor(minor);

	mutex_lock(&comedi_dev->mutex);
	if (comedi_dev->attached)
	ret = -EBUSY;
	else if (!try_module_get(driver->module))
	ret = -EIO;
	else {
	comedi_set_hw_dev(comedi_dev, hardware_device);
	comedi_dev->driver = driver;
	ret = driver->auto_attach(comedi_dev, context);
	if (ret < 0) {
	module_put(driver->module);
	__comedi_device_detach(comedi_dev);
	} else {
	ret = comedi_device_postconfig(comedi_dev);
	}
	}
	mutex_unlock(&comedi_dev->mutex);

	if (ret < 0)
	comedi_free_board_minor(minor);
	return ret;
	}
	EXPORT_SYMBOL_GPL(comedi_auto_config);

	void comedi_auto_unconfig(struct device *hardware_device)
	{
	int minor;

	if (hardware_device == NULL)
	return;
	minor = comedi_find_board_minor(hardware_device);
	if (minor < 0)
	return;
	comedi_free_board_minor(minor);
	}
	EXPORT_SYMBOL_GPL(comedi_auto_unconfig);

	int comedi_driver_register(struct comedi_driver *driver)
	{
	driver->next = comedi_drivers;
	comedi_drivers = driver;

	return 0;
	}
	EXPORT_SYMBOL(comedi_driver_register);

	int comedi_driver_unregister(struct comedi_driver *driver)
	{
	struct comedi_driver *prev;
	int i;

	/* check for devices using this driver */
	for (i = 0; i < COMEDI_NUM_BOARD_MINORS; i++) {
	struct comedi_device *dev = comedi_dev_from_minor(i);

	if (!dev)
	continue;

	mutex_lock(&dev->mutex);
	if (dev->attached && dev->driver == driver) {
	if (dev->use_count)
	dev_warn(dev->class_dev,
	"BUG! detaching device with use_count=%d\n",
	dev->use_count);
	comedi_device_detach(dev);
	}
	mutex_unlock(&dev->mutex);
	}

	if (comedi_drivers == driver) {
	comedi_drivers = driver->next;
	return 0;
	}

	for (prev = comedi_drivers; prev->next; prev = prev->next) {
	if (prev->next == driver) {
	prev->next = driver->next;
	return 0;
	}
	}
	return -EINVAL;
	}
	EXPORT_SYMBOL(comedi_driver_unregister);