PCI: endpoint: Assign function number for each PF in EPC core

The PCIe endpoint core relies on the drivers that invoke the
pci_epc_add_epf() API to allocate and assign a function number
to each physical function (PF). Since endpoint function device can
be created by multiple mechanisms (configfs, devicetree, etc..),
allowing each of these mechanisms to assign a function number
would result in mutliple endpoint function devices having the
same function number. In order to avoid this, let EPC core assign
a function number to the endpoint device.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>

include/linux/pci-epc.h

@@ -92,6 +92,7 @@ struct pci_epc_mem {
  * @max_functions: max number of functions that can be configured in this EPC
  * @group: configfs group representing the PCI EPC device
  * @lock: mutex to protect pci_epc ops
+ * @function_num_map: bitmap to manage physical function number
  * @notifier: used to notify EPF of any EPC events (like linkup)
  */
 struct pci_epc {
@@ -103,6 +104,7 @@ struct pci_epc {
 	struct config_group		*group;
 	/* mutex to protect against concurrent access of EP controller */
 	struct mutex			lock;
+	unsigned long			function_num_map;
 	struct atomic_notifier_head	notifier;
 };