/**

* 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 to 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());
spin_lock(&pci_bus_lock);
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:
pci_dev_put(from);
dev = pci_dev_get(dev);
spin_unlock(&pci_bus_lock);
return dev;
}