drivers/xen/xen-pciback/conf_space.c - kernel/msm-4.9 - Gitiles

 /*
  * PCI Backend - Functions for creating a virtual configuration space for
  *               exported PCI Devices.
  *               It's dangerous to allow PCI Driver Domains to change their
  *               device's resources (memory, i/o ports, interrupts). We need to
  *               restrict changes to certain PCI Configuration registers:
  *               BARs, INTERRUPT_PIN, most registers in the header...
  *
  * Author: Ryan Wilson <hap9@epoch.ncsc.mil>
  */

 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/pci.h>
 #include "pciback.h"
 #include "conf_space.h"
 #include "conf_space_quirks.h"

 static bool permissive;
 module_param(permissive, bool, 0644);

 /* This is where xen_pcibk_read_config_byte, xen_pcibk_read_config_word,
  * xen_pcibk_write_config_word, and xen_pcibk_write_config_byte are created. */
 #define DEFINE_PCI_CONFIG(op, size, type)			\
 int xen_pcibk_##op##_config_##size				\
 (struct pci_dev *dev, int offset, type value, void *data)	\
 {								\
 	return pci_##op##_config_##size(dev, offset, value);	\
 }

 DEFINE_PCI_CONFIG(read, byte, u8 *)
 DEFINE_PCI_CONFIG(read, word, u16 *)
 DEFINE_PCI_CONFIG(read, dword, u32 *)

 DEFINE_PCI_CONFIG(write, byte, u8)
 DEFINE_PCI_CONFIG(write, word, u16)
 DEFINE_PCI_CONFIG(write, dword, u32)

 static int conf_space_read(struct pci_dev *dev,
 			   const struct config_field_entry *entry,
 			   int offset, u32 *value)
 {
 	int ret = 0;
 	const struct config_field *field = entry->field;

 	*value = 0;

 	switch (field->size) {
 	case 1:
 		if (field->u.b.read)
 			ret = field->u.b.read(dev, offset, (u8 *) value,
 					      entry->data);
 		break;
 	case 2:
 		if (field->u.w.read)
 			ret = field->u.w.read(dev, offset, (u16 *) value,
 					      entry->data);
 		break;
 	case 4:
 		if (field->u.dw.read)
 			ret = field->u.dw.read(dev, offset, value, entry->data);
 		break;
 	}
 	return ret;
 }

 static int conf_space_write(struct pci_dev *dev,
 			    const struct config_field_entry *entry,
 			    int offset, u32 value)
 {
 	int ret = 0;
 	const struct config_field *field = entry->field;

 	switch (field->size) {
 	case 1:
 		if (field->u.b.write)
 			ret = field->u.b.write(dev, offset, (u8) value,
 					       entry->data);
 		break;
 	case 2:
 		if (field->u.w.write)
 			ret = field->u.w.write(dev, offset, (u16) value,
 					       entry->data);
 		break;
 	case 4:
 		if (field->u.dw.write)
 			ret = field->u.dw.write(dev, offset, value,
 						entry->data);
 		break;
 	}
 	return ret;
 }

 static inline u32 get_mask(int size)
 {
 	if (size == 1)
 		return 0xff;
 	else if (size == 2)
 		return 0xffff;
 	else
 		return 0xffffffff;
 }

 static inline int valid_request(int offset, int size)
 {
 	/* Validate request (no un-aligned requests) */
 	if ((size == 1 || size == 2 || size == 4) && (offset % size) == 0)
 		return 1;
 	return 0;
 }

 static inline u32 merge_value(u32 val, u32 new_val, u32 new_val_mask,
 			      int offset)
 {
 	if (offset >= 0) {
 		new_val_mask <<= (offset * 8);
 		new_val <<= (offset * 8);
 	} else {
 		new_val_mask >>= (offset * -8);
 		new_val >>= (offset * -8);
 	}
 	val = (val & ~new_val_mask) | (new_val & new_val_mask);

 	return val;
 }

 static int xen_pcibios_err_to_errno(int err)
 {
 	switch (err) {
 	case PCIBIOS_SUCCESSFUL:
 		return XEN_PCI_ERR_success;
 	case PCIBIOS_DEVICE_NOT_FOUND:
 		return XEN_PCI_ERR_dev_not_found;
 	case PCIBIOS_BAD_REGISTER_NUMBER:
 		return XEN_PCI_ERR_invalid_offset;
 	case PCIBIOS_FUNC_NOT_SUPPORTED:
 		return XEN_PCI_ERR_not_implemented;
 	case PCIBIOS_SET_FAILED:
 		return XEN_PCI_ERR_access_denied;
 	}
 	return err;
 }

 int xen_pcibk_config_read(struct pci_dev *dev, int offset, int size,
 			  u32 *ret_val)
 {
 	int err = 0;
 	struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(dev);
 	const struct config_field_entry *cfg_entry;
 	const struct config_field *field;
 	int req_start, req_end, field_start, field_end;
 	/* if read fails for any reason, return 0
 	 * (as if device didn't respond) */
 	u32 value = 0, tmp_val;

 	if (unlikely(verbose_request))
 		printk(KERN_DEBUG DRV_NAME ": %s: read %d bytes at 0x%x\n",
 		       pci_name(dev), size, offset);

 	if (!valid_request(offset, size)) {
 		err = XEN_PCI_ERR_invalid_offset;
 		goto out;
 	}

 	/* Get the real value first, then modify as appropriate */
 	switch (size) {
 	case 1:
 		err = pci_read_config_byte(dev, offset, (u8 *) &value);
 		break;
 	case 2:
 		err = pci_read_config_word(dev, offset, (u16 *) &value);
 		break;
 	case 4:
 		err = pci_read_config_dword(dev, offset, &value);
 		break;
 	}

 	list_for_each_entry(cfg_entry, &dev_data->config_fields, list) {
 		field = cfg_entry->field;

 		req_start = offset;
 		req_end = offset + size;
 		field_start = OFFSET(cfg_entry);
 		field_end = OFFSET(cfg_entry) + field->size;

 		if ((req_start >= field_start && req_start < field_end)
 		    || (req_end > field_start && req_end <= field_end)) {
 			err = conf_space_read(dev, cfg_entry, field_start,
 					      &tmp_val);
 			if (err)
 				goto out;

 			value = merge_value(value, tmp_val,
 					    get_mask(field->size),
 					    field_start - req_start);
 		}
 	}

 out:
 	if (unlikely(verbose_request))
 		printk(KERN_DEBUG DRV_NAME ": %s: read %d bytes at 0x%x = %x\n",
 		       pci_name(dev), size, offset, value);

 	*ret_val = value;
 	return xen_pcibios_err_to_errno(err);
 }

 int xen_pcibk_config_write(struct pci_dev *dev, int offset, int size, u32 value)
 {
 	int err = 0, handled = 0;
 	struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(dev);
 	const struct config_field_entry *cfg_entry;
 	const struct config_field *field;
 	u32 tmp_val;
 	int req_start, req_end, field_start, field_end;

 	if (unlikely(verbose_request))
 		printk(KERN_DEBUG
 		       DRV_NAME ": %s: write request %d bytes at 0x%x = %x\n",
 		       pci_name(dev), size, offset, value);

 	if (!valid_request(offset, size))
 		return XEN_PCI_ERR_invalid_offset;

 	list_for_each_entry(cfg_entry, &dev_data->config_fields, list) {
 		field = cfg_entry->field;

 		req_start = offset;
 		req_end = offset + size;
 		field_start = OFFSET(cfg_entry);
 		field_end = OFFSET(cfg_entry) + field->size;

 		if ((req_start >= field_start && req_start < field_end)
 		    || (req_end > field_start && req_end <= field_end)) {
 			tmp_val = 0;

 			err = xen_pcibk_config_read(dev, field_start,
 						  field->size, &tmp_val);
 			if (err)
 				break;

 			tmp_val = merge_value(tmp_val, value, get_mask(size),
 					      req_start - field_start);

 			err = conf_space_write(dev, cfg_entry, field_start,
 					       tmp_val);

 			/* handled is set true here, but not every byte
 			 * may have been written! Properly detecting if
 			 * every byte is handled is unnecessary as the
 			 * flag is used to detect devices that need
 			 * special helpers to work correctly.
 			 */
 			handled = 1;
 		}
 	}

 	if (!handled && !err) {
 		/* By default, anything not specificially handled above is
 		 * read-only. The permissive flag changes this behavior so
 		 * that anything not specifically handled above is writable.
 		 * This means that some fields may still be read-only because
 		 * they have entries in the config_field list that intercept
 		 * the write and do nothing. */
 		if (dev_data->permissive || permissive) {
 			switch (size) {
 			case 1:
 				err = pci_write_config_byte(dev, offset,
 							    (u8) value);
 				break;
 			case 2:
 				err = pci_write_config_word(dev, offset,
 							    (u16) value);
 				break;
 			case 4:
 				err = pci_write_config_dword(dev, offset,
 							     (u32) value);
 				break;
 			}
 		} else if (!dev_data->warned_on_write) {
 			dev_data->warned_on_write = 1;
 			dev_warn(&dev->dev, "Driver tried to write to a "
 				 "read-only configuration space field at offset"
 				 " 0x%x, size %d. This may be harmless, but if "
 				 "you have problems with your device:\n"
 				 "1) see permissive attribute in sysfs\n"
 				 "2) report problems to the xen-devel "
 				 "mailing list along with details of your "
 				 "device obtained from lspci.\n", offset, size);
 		}
 	}

 	return xen_pcibios_err_to_errno(err);
 }

 void xen_pcibk_config_free_dyn_fields(struct pci_dev *dev)
 {
 	struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(dev);
 	struct config_field_entry *cfg_entry, *t;
 	const struct config_field *field;

 	dev_dbg(&dev->dev, "free-ing dynamically allocated virtual "
 			   "configuration space fields\n");
 	if (!dev_data)
 		return;

 	list_for_each_entry_safe(cfg_entry, t, &dev_data->config_fields, list) {
 		field = cfg_entry->field;

 		if (field->clean) {
 			field->clean((struct config_field *)field);

 			kfree(cfg_entry->data);

 			list_del(&cfg_entry->list);
 			kfree(cfg_entry);
 		}

 	}
 }

 void xen_pcibk_config_reset_dev(struct pci_dev *dev)
 {
 	struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(dev);
 	const struct config_field_entry *cfg_entry;
 	const struct config_field *field;

 	dev_dbg(&dev->dev, "resetting virtual configuration space\n");
 	if (!dev_data)
 		return;

 	list_for_each_entry(cfg_entry, &dev_data->config_fields, list) {
 		field = cfg_entry->field;

 		if (field->reset)
 			field->reset(dev, OFFSET(cfg_entry), cfg_entry->data);
 	}
 }

 void xen_pcibk_config_free_dev(struct pci_dev *dev)
 {
 	struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(dev);
 	struct config_field_entry *cfg_entry, *t;
 	const struct config_field *field;

 	dev_dbg(&dev->dev, "free-ing virtual configuration space fields\n");
 	if (!dev_data)
 		return;

 	list_for_each_entry_safe(cfg_entry, t, &dev_data->config_fields, list) {
 		list_del(&cfg_entry->list);

 		field = cfg_entry->field;

 		if (field->release)
 			field->release(dev, OFFSET(cfg_entry), cfg_entry->data);

 		kfree(cfg_entry);
 	}
 }

 int xen_pcibk_config_add_field_offset(struct pci_dev *dev,
 				    const struct config_field *field,
 				    unsigned int base_offset)
 {
 	int err = 0;
 	struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(dev);
 	struct config_field_entry *cfg_entry;
 	void *tmp;

 	cfg_entry = kmalloc(sizeof(*cfg_entry), GFP_KERNEL);
 	if (!cfg_entry) {
 		err = -ENOMEM;
 		goto out;
 	}

 	cfg_entry->data = NULL;
 	cfg_entry->field = field;
 	cfg_entry->base_offset = base_offset;

 	/* silently ignore duplicate fields */
 	err = xen_pcibk_field_is_dup(dev, OFFSET(cfg_entry));
 	if (err)
 		goto out;

 	if (field->init) {
 		tmp = field->init(dev, OFFSET(cfg_entry));

 		if (IS_ERR(tmp)) {
 			err = PTR_ERR(tmp);
 			goto out;
 		}

 		cfg_entry->data = tmp;
 	}

 	dev_dbg(&dev->dev, "added config field at offset 0x%02x\n",
 		OFFSET(cfg_entry));
 	list_add_tail(&cfg_entry->list, &dev_data->config_fields);

 out:
 	if (err)
 		kfree(cfg_entry);

 	return err;
 }

 /* This sets up the device's virtual configuration space to keep track of
  * certain registers (like the base address registers (BARs) so that we can
  * keep the client from manipulating them directly.
  */
 int xen_pcibk_config_init_dev(struct pci_dev *dev)
 {
 	int err = 0;
 	struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(dev);

 	dev_dbg(&dev->dev, "initializing virtual configuration space\n");

 	INIT_LIST_HEAD(&dev_data->config_fields);

 	err = xen_pcibk_config_header_add_fields(dev);
 	if (err)
 		goto out;

 	err = xen_pcibk_config_capability_add_fields(dev);
 	if (err)
 		goto out;

 	err = xen_pcibk_config_quirks_init(dev);

 out:
 	return err;
 }

 int xen_pcibk_config_init(void)
 {
 	return xen_pcibk_config_capability_init();
 }
	/*
	* PCI Backend - Functions for creating a virtual configuration space for
	* exported PCI Devices.
	* It's dangerous to allow PCI Driver Domains to change their
	* device's resources (memory, i/o ports, interrupts). We need to
	* restrict changes to certain PCI Configuration registers:
	* BARs, INTERRUPT_PIN, most registers in the header...
	*
	* Author: Ryan Wilson <hap9@epoch.ncsc.mil>
	*/

	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/pci.h>
	#include "pciback.h"
	#include "conf_space.h"
	#include "conf_space_quirks.h"

	static bool permissive;
	module_param(permissive, bool, 0644);

	/* This is where xen_pcibk_read_config_byte, xen_pcibk_read_config_word,
	* xen_pcibk_write_config_word, and xen_pcibk_write_config_byte are created. */
	#define DEFINE_PCI_CONFIG(op, size, type) \
	int xen_pcibk_##op##_config_##size \
	(struct pci_dev dev, int offset, type value, void data) \
	{ \
	return pci_##op##_config_##size(dev, offset, value); \
	}

	DEFINE_PCI_CONFIG(read, byte, u8 *)
	DEFINE_PCI_CONFIG(read, word, u16 *)
	DEFINE_PCI_CONFIG(read, dword, u32 *)

	DEFINE_PCI_CONFIG(write, byte, u8)
	DEFINE_PCI_CONFIG(write, word, u16)
	DEFINE_PCI_CONFIG(write, dword, u32)

	static int conf_space_read(struct pci_dev *dev,
	const struct config_field_entry *entry,
	int offset, u32 *value)
	{
	int ret = 0;
	const struct config_field *field = entry->field;

	*value = 0;

	switch (field->size) {
	case 1:
	if (field->u.b.read)
	ret = field->u.b.read(dev, offset, (u8 *) value,
	entry->data);
	break;
	case 2:
	if (field->u.w.read)
	ret = field->u.w.read(dev, offset, (u16 *) value,
	entry->data);
	break;
	case 4:
	if (field->u.dw.read)
	ret = field->u.dw.read(dev, offset, value, entry->data);
	break;
	}
	return ret;
	}

	static int conf_space_write(struct pci_dev *dev,
	const struct config_field_entry *entry,
	int offset, u32 value)
	{
	int ret = 0;
	const struct config_field *field = entry->field;

	switch (field->size) {
	case 1:
	if (field->u.b.write)
	ret = field->u.b.write(dev, offset, (u8) value,
	entry->data);
	break;
	case 2:
	if (field->u.w.write)
	ret = field->u.w.write(dev, offset, (u16) value,
	entry->data);
	break;
	case 4:
	if (field->u.dw.write)
	ret = field->u.dw.write(dev, offset, value,
	entry->data);
	break;
	}
	return ret;
	}

	static inline u32 get_mask(int size)
	{
	if (size == 1)
	return 0xff;
	else if (size == 2)
	return 0xffff;
	else
	return 0xffffffff;
	}

	static inline int valid_request(int offset, int size)
	{
	/* Validate request (no un-aligned requests) */
	if ((size == 1 \|\| size == 2 \|\| size == 4) && (offset % size) == 0)
	return 1;
	return 0;
	}

	static inline u32 merge_value(u32 val, u32 new_val, u32 new_val_mask,
	int offset)
	{
	if (offset >= 0) {
	new_val_mask <<= (offset * 8);
	new_val <<= (offset * 8);
	} else {
	new_val_mask >>= (offset * -8);
	new_val >>= (offset * -8);
	}
	val = (val & ~new_val_mask) \| (new_val & new_val_mask);

	return val;
	}

	static int xen_pcibios_err_to_errno(int err)
	{
	switch (err) {
	case PCIBIOS_SUCCESSFUL:
	return XEN_PCI_ERR_success;
	case PCIBIOS_DEVICE_NOT_FOUND:
	return XEN_PCI_ERR_dev_not_found;
	case PCIBIOS_BAD_REGISTER_NUMBER:
	return XEN_PCI_ERR_invalid_offset;
	case PCIBIOS_FUNC_NOT_SUPPORTED:
	return XEN_PCI_ERR_not_implemented;
	case PCIBIOS_SET_FAILED:
	return XEN_PCI_ERR_access_denied;
	}
	return err;
	}

	int xen_pcibk_config_read(struct pci_dev *dev, int offset, int size,
	u32 *ret_val)
	{
	int err = 0;
	struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(dev);
	const struct config_field_entry *cfg_entry;
	const struct config_field *field;
	int req_start, req_end, field_start, field_end;
	/* if read fails for any reason, return 0
	* (as if device didn't respond) */
	u32 value = 0, tmp_val;

	if (unlikely(verbose_request))
	printk(KERN_DEBUG DRV_NAME ": %s: read %d bytes at 0x%x\n",
	pci_name(dev), size, offset);

	if (!valid_request(offset, size)) {
	err = XEN_PCI_ERR_invalid_offset;
	goto out;
	}

	/* Get the real value first, then modify as appropriate */
	switch (size) {
	case 1:
	err = pci_read_config_byte(dev, offset, (u8 *) &value);
	break;
	case 2:
	err = pci_read_config_word(dev, offset, (u16 *) &value);
	break;
	case 4:
	err = pci_read_config_dword(dev, offset, &value);
	break;
	}

	list_for_each_entry(cfg_entry, &dev_data->config_fields, list) {
	field = cfg_entry->field;

	req_start = offset;
	req_end = offset + size;
	field_start = OFFSET(cfg_entry);
	field_end = OFFSET(cfg_entry) + field->size;

	if ((req_start >= field_start && req_start < field_end)
	\|\| (req_end > field_start && req_end <= field_end)) {
	err = conf_space_read(dev, cfg_entry, field_start,
	&tmp_val);
	if (err)
	goto out;

	value = merge_value(value, tmp_val,
	get_mask(field->size),
	field_start - req_start);
	}
	}

	out:
	if (unlikely(verbose_request))
	printk(KERN_DEBUG DRV_NAME ": %s: read %d bytes at 0x%x = %x\n",
	pci_name(dev), size, offset, value);

	*ret_val = value;
	return xen_pcibios_err_to_errno(err);
	}

	int xen_pcibk_config_write(struct pci_dev *dev, int offset, int size, u32 value)
	{
	int err = 0, handled = 0;
	struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(dev);
	const struct config_field_entry *cfg_entry;
	const struct config_field *field;
	u32 tmp_val;
	int req_start, req_end, field_start, field_end;

	if (unlikely(verbose_request))
	printk(KERN_DEBUG
	DRV_NAME ": %s: write request %d bytes at 0x%x = %x\n",
	pci_name(dev), size, offset, value);

	if (!valid_request(offset, size))
	return XEN_PCI_ERR_invalid_offset;

	list_for_each_entry(cfg_entry, &dev_data->config_fields, list) {
	field = cfg_entry->field;

	req_start = offset;
	req_end = offset + size;
	field_start = OFFSET(cfg_entry);
	field_end = OFFSET(cfg_entry) + field->size;

	if ((req_start >= field_start && req_start < field_end)
	\|\| (req_end > field_start && req_end <= field_end)) {
	tmp_val = 0;

	err = xen_pcibk_config_read(dev, field_start,
	field->size, &tmp_val);
	if (err)
	break;

	tmp_val = merge_value(tmp_val, value, get_mask(size),
	req_start - field_start);

	err = conf_space_write(dev, cfg_entry, field_start,
	tmp_val);

	/* handled is set true here, but not every byte
	* may have been written! Properly detecting if
	* every byte is handled is unnecessary as the
	* flag is used to detect devices that need
	* special helpers to work correctly.
	*/
	handled = 1;
	}
	}

	if (!handled && !err) {
	/* By default, anything not specificially handled above is
	* read-only. The permissive flag changes this behavior so
	* that anything not specifically handled above is writable.
	* This means that some fields may still be read-only because
	* they have entries in the config_field list that intercept
	* the write and do nothing. */
	if (dev_data->permissive \|\| permissive) {
	switch (size) {
	case 1:
	err = pci_write_config_byte(dev, offset,
	(u8) value);
	break;
	case 2:
	err = pci_write_config_word(dev, offset,
	(u16) value);
	break;
	case 4:
	err = pci_write_config_dword(dev, offset,
	(u32) value);
	break;
	}
	} else if (!dev_data->warned_on_write) {
	dev_data->warned_on_write = 1;
	dev_warn(&dev->dev, "Driver tried to write to a "
	"read-only configuration space field at offset"
	" 0x%x, size %d. This may be harmless, but if "
	"you have problems with your device:\n"
	"1) see permissive attribute in sysfs\n"
	"2) report problems to the xen-devel "
	"mailing list along with details of your "
	"device obtained from lspci.\n", offset, size);
	}
	}

	return xen_pcibios_err_to_errno(err);
	}

	void xen_pcibk_config_free_dyn_fields(struct pci_dev *dev)
	{
	struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(dev);
	struct config_field_entry cfg_entry, t;
	const struct config_field *field;

	dev_dbg(&dev->dev, "free-ing dynamically allocated virtual "
	"configuration space fields\n");
	if (!dev_data)
	return;

	list_for_each_entry_safe(cfg_entry, t, &dev_data->config_fields, list) {
	field = cfg_entry->field;

	if (field->clean) {
	field->clean((struct config_field *)field);

	kfree(cfg_entry->data);

	list_del(&cfg_entry->list);
	kfree(cfg_entry);
	}

	}
	}

	void xen_pcibk_config_reset_dev(struct pci_dev *dev)
	{
	struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(dev);
	const struct config_field_entry *cfg_entry;
	const struct config_field *field;

	dev_dbg(&dev->dev, "resetting virtual configuration space\n");
	if (!dev_data)
	return;

	list_for_each_entry(cfg_entry, &dev_data->config_fields, list) {
	field = cfg_entry->field;

	if (field->reset)
	field->reset(dev, OFFSET(cfg_entry), cfg_entry->data);
	}
	}

	void xen_pcibk_config_free_dev(struct pci_dev *dev)
	{
	struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(dev);
	struct config_field_entry cfg_entry, t;
	const struct config_field *field;

	dev_dbg(&dev->dev, "free-ing virtual configuration space fields\n");
	if (!dev_data)
	return;

	list_for_each_entry_safe(cfg_entry, t, &dev_data->config_fields, list) {
	list_del(&cfg_entry->list);

	field = cfg_entry->field;

	if (field->release)
	field->release(dev, OFFSET(cfg_entry), cfg_entry->data);

	kfree(cfg_entry);
	}
	}

	int xen_pcibk_config_add_field_offset(struct pci_dev *dev,
	const struct config_field *field,
	unsigned int base_offset)
	{
	int err = 0;
	struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(dev);
	struct config_field_entry *cfg_entry;
	void *tmp;

	cfg_entry = kmalloc(sizeof(*cfg_entry), GFP_KERNEL);
	if (!cfg_entry) {
	err = -ENOMEM;
	goto out;
	}

	cfg_entry->data = NULL;
	cfg_entry->field = field;
	cfg_entry->base_offset = base_offset;

	/* silently ignore duplicate fields */
	err = xen_pcibk_field_is_dup(dev, OFFSET(cfg_entry));
	if (err)
	goto out;

	if (field->init) {
	tmp = field->init(dev, OFFSET(cfg_entry));

	if (IS_ERR(tmp)) {
	err = PTR_ERR(tmp);
	goto out;
	}

	cfg_entry->data = tmp;
	}

	dev_dbg(&dev->dev, "added config field at offset 0x%02x\n",
	OFFSET(cfg_entry));
	list_add_tail(&cfg_entry->list, &dev_data->config_fields);

	out:
	if (err)
	kfree(cfg_entry);

	return err;
	}

	/* This sets up the device's virtual configuration space to keep track of
	* certain registers (like the base address registers (BARs) so that we can
	* keep the client from manipulating them directly.
	*/
	int xen_pcibk_config_init_dev(struct pci_dev *dev)
	{
	int err = 0;
	struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(dev);

	dev_dbg(&dev->dev, "initializing virtual configuration space\n");

	INIT_LIST_HEAD(&dev_data->config_fields);

	err = xen_pcibk_config_header_add_fields(dev);
	if (err)
	goto out;

	err = xen_pcibk_config_capability_add_fields(dev);
	if (err)
	goto out;

	err = xen_pcibk_config_quirks_init(dev);

	out:
	return err;
	}

	int xen_pcibk_config_init(void)
	{
	return xen_pcibk_config_capability_init();
	}