search.c

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	n = from ? from->global_list.next : pci_devices.next;

	while (n && (n != &pci_devices)) {
		dev = pci_dev_g(n);
		if ((vendor == PCI_ANY_ID || dev->vendor == vendor) &&
		    (device == PCI_ANY_ID || dev->device == device) &&
		    (ss_vendor == PCI_ANY_ID || dev->subsystem_vendor == ss_vendor) &&
		    (ss_device == PCI_ANY_ID || dev->subsystem_device == ss_device))
			goto exit;
		n = n->next;
	}
	dev = NULL;
exit:
	up_read(&pci_bus_sem);
	return dev;
}

/**
 * pci_find_device - begin or continue searching for a PCI device by vendor/device id
 * @vendor: PCI vendor id to match, or %PCI_ANY_ID to match all vendor ids
 * @device: PCI device id to match, or %PCI_ANY_ID to match all device ids
 * @from: Previous PCI device found in search, or %NULL for new search.
 *
 * Iterates through the list of known PCI devices.  If a PCI device is found
 * with a matching @vendor and @device, a pointer to its device structure is
 * returned.  Otherwise, %NULL is returned.
 * A new search is initiated by passing %NULL as the @from argument.
 * Otherwise if @from is not %NULL, searches continue from next device
 * on the global list.
 * 
 * NOTE: Do not use this function any more; use pci_get_device() instead, as
 * the PCI device returned by this function can disappear at any moment in
 * time.
 */
struct pci_dev *
pci_find_device(unsigned int vendor, unsigned int device, const struct pci_dev *from)
{
	return pci_find_subsys(vendor, device, PCI_ANY_ID, PCI_ANY_ID, from);
}
#endif /* CONFIG_PCI_LEGACY */

/**
 * pci_get_subsys - begin or continue searching for a PCI device by vendor/subvendor/device/subdevice id
 * @vendor: PCI vendor id to match, or %PCI_ANY_ID to match all vendor ids
 * @device: PCI device id to match, or %PCI_ANY_ID to match all device ids
 * @ss_vendor: PCI subsystem vendor id to match, or %PCI_ANY_ID to match all vendor ids
 * @ss_device: PCI subsystem device id to match, or %PCI_ANY_ID to match all device ids
 * @from: Previous PCI device found in search, or %NULL for new search.
 *
 * Iterates through the list of known PCI devices.  If a PCI device is found
 * with a matching @vendor, @device, @ss_vendor and @ss_device, a pointer to its
 * device structure is returned, and the reference count to the device is
 * incremented.  Otherwise, %NULL is returned.  A new search is initiated by
 * passing %NULL as the @from argument.  Otherwise if @from is not %NULL,
 * searches continue from next device on the global list.
 * The reference count for @from is always decremented if it is not %NULL.
 */
struct pci_dev * 
pci_get_subsys(unsigned int vendor, unsigned int device,
	       unsigned int ss_vendor, unsigned int ss_device,
	       struct pci_dev *from)
{
	struct list_head *n;
	struct pci_dev *dev;

	WARN_ON(in_interrupt());

	/*
	 * pci_get_subsys() can potentially be called by drivers super-early
	 * in boot.  But the down_read() will enable local interrupts, which
	 * can cause some machines to crash.  So here we detect and flag that
	 * situation and bail out early.
	 */
	if (unlikely(no_pci_devices()))
		return NULL;
	down_read(&pci_bus_sem);
	n = from ? from->global_list.next : pci_devices.next;

	while (n && (n != &pci_devices)) {
		dev = pci_dev_g(n);
		if ((vendor == PCI_ANY_ID || dev->vendor == vendor) &&
		    (device == PCI_ANY_ID || dev->device == device) &&
		    (ss_vendor == PCI_ANY_ID || dev->subsystem_vendor == ss_vendor) &&
		    (ss_device == PCI_ANY_ID || dev->subsystem_device == ss_device))
			goto exit;
		n = n->next;
	}
	dev = NULL;
exit:
	dev = pci_dev_get(dev);
	up_read(&pci_bus_sem);
	pci_dev_put(from);
	return dev;
}

/**
 * pci_get_device - begin or continue searching for a PCI device by vendor/device id
 * @vendor: PCI vendor id to match, or %PCI_ANY_ID to match all vendor ids
 * @device: PCI device id to match, or %PCI_ANY_ID to match all device ids
 * @from: Previous PCI device found in search, or %NULL for new search.
 *
 * Iterates through the list of known PCI devices.  If a PCI device is
 * found with a matching @vendor and @device, the reference count to the
 * device is incremented and a pointer to its device structure is returned.
 * Otherwise, %NULL is returned.  A new search is initiated by passing %NULL
 * as the @from argument.  Otherwise if @from is not %NULL, searches continue
 * from next device on the global list.  The reference count for @from is
 * always decremented if it is not %NULL.
 */
struct pci_dev *
pci_get_device(unsigned int vendor, unsigned int device, struct pci_dev *from)
{
	return pci_get_subsys(vendor, device, PCI_ANY_ID, PCI_ANY_ID, from);
}

/**
 * pci_get_device_reverse - begin or continue searching for a PCI device by vendor/device id
 * @vendor: PCI vendor id to match, or %PCI_ANY_ID to match all vendor ids
 * @device: PCI device id to match, or %PCI_ANY_ID to match all device ids
 * @from: Previous PCI device found in search, or %NULL for new search.
 *
 * Iterates through the list of known PCI devices in the reverse order of
 * pci_get_device.
 * If a PCI device is found with a matching @vendor and @device, the reference
 * count to the  device is incremented and a pointer to its device structure
 * is returned Otherwise, %NULL is returned.  A new search is initiated by
 * passing %NULL as the @from argument.  Otherwise if @from is not %NULL,
 * searches continue from next device on the global list.  The reference
 * count for @from is always decremented if it is not %NULL.
 */
struct pci_dev *
pci_get_device_reverse(unsigned int vendor, unsigned int device, struct pci_dev *from)
{
	struct list_head *n;
	struct pci_dev *dev;

	WARN_ON(in_interrupt());
	down_read(&pci_bus_sem);
	n = from ? from->global_list.prev : pci_devices.prev;

	while (n && (n != &pci_devices)) {
		dev = pci_dev_g(n);
		if ((vendor == PCI_ANY_ID || dev->vendor == vendor) &&
		    (device == PCI_ANY_ID || dev->device == device))
			goto exit;
		n = n->prev;
	}
	dev = NULL;
exit:
	dev = pci_dev_get(dev);
	up_read(&pci_bus_sem);
	pci_dev_put(from);
	return dev;
}

/**
 * pci_get_class - begin or continue searching for a PCI device by class
 * @class: search for a PCI device with this class designation
 * @from: Previous PCI device found in search, or %NULL for new search.
 *
 * Iterates through the list of known PCI devices.  If a PCI device is
 * found with a matching @class, the reference count to the device is
 * incremented and a pointer to its device structure is returned.
 * Otherwise, %NULL is returned.
 * A new search is initiated by passing %NULL as the @from argument.
 * Otherwise if @from is not %NULL, searches continue from next device
 * on the global list.  The reference count for @from is always decremented
 * if it is not %NULL.
 */
struct pci_dev *pci_get_class(unsigned int class, struct pci_dev *from)
{
	struct list_head *n;
	struct pci_dev *dev;

	WARN_ON(in_interrupt());
	down_read(&pci_bus_sem);
	n = from ? from->global_list.next : pci_devices.next;

	while (n && (n != &pci_devices)) {
		dev = pci_dev_g(n);
		if (dev->class == class)
			goto exit;
		n = n->next;
	}
	dev = NULL;
exit:
	dev = pci_dev_get(dev);
	up_read(&pci_bus_sem);
	pci_dev_put(from);
	return dev;
}

const struct pci_device_id *pci_find_present(const struct pci_device_id *ids)
{
	struct pci_dev *dev;
	const struct pci_device_id *found = NULL;

	WARN_ON(in_interrupt());
	down_read(&pci_bus_sem);
	while (ids->vendor || ids->subvendor || ids->class_mask) {
		list_for_each_entry(dev, &pci_devices, global_list) {
			if ((found = pci_match_one_device(ids, dev)) != NULL)
				goto exit;
		}
		ids++;
	}
exit:
	up_read(&pci_bus_sem);
	return found;
}

/**
 * pci_dev_present - Returns 1 if device matching the device list is present, 0 if not.
 * @ids: A pointer to a null terminated list of struct pci_device_id structures
 * that describe the type of PCI device the caller is trying to find.
 *
 * Obvious fact: You do not have a reference to any device that might be found
 * by this function, so if that device is removed from the system right after
 * this function is finished, the value will be stale.  Use this function to
 * find devices that are usually built into a system, or for a general hint as
 * to if another device happens to be present at this specific moment in time.
 */
int pci_dev_present(const struct pci_device_id *ids)
{
	return pci_find_present(ids) == NULL ? 0 : 1;
}

EXPORT_SYMBOL(pci_dev_present);
EXPORT_SYMBOL(pci_find_present);

#ifdef CONFIG_PCI_LEGACY
EXPORT_SYMBOL(pci_find_device);
EXPORT_SYMBOL(pci_find_slot);
#endif /* CONFIG_PCI_LEGACY */

/* For boot time work */
EXPORT_SYMBOL(pci_find_bus);
EXPORT_SYMBOL(pci_find_next_bus);
/* For everyone */
EXPORT_SYMBOL(pci_get_device);
EXPORT_SYMBOL(pci_get_device_reverse);
EXPORT_SYMBOL(pci_get_subsys);
EXPORT_SYMBOL(pci_get_slot);
EXPORT_SYMBOL(pci_get_bus_and_slot);
EXPORT_SYMBOL(pci_get_class);