PCI: endpoint: Add new pci_epc_ops to get EPC features

Add a new pci_epc_ops ->get_features() to get the features
supported by the EPC. Since EPC can provide different features to
different functions, the ->get_features() ops takes _func_no_ as
an argument.

Tested-by: Gustavo Pimentel <gustavo.pimentel@synopsys.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>

drivers/pci/endpoint/pci-epc-core.c

@@ -83,6 +83,36 @@ err:
 }
 EXPORT_SYMBOL_GPL(pci_epc_get);
 
+/**
+ * pci_epc_get_features() - get the features supported by EPC
+ * @epc: the features supported by *this* EPC device will be returned
+ * @func_no: the features supported by the EPC device specific to the
+ *	     endpoint function with func_no will be returned
+ *
+ * Invoke to get the features provided by the EPC which may be
+ * specific to an endpoint function. Returns pci_epc_features on success
+ * and NULL for any failures.
+ */
+const struct pci_epc_features *pci_epc_get_features(struct pci_epc *epc,
+						    u8 func_no)
+{
+	const struct pci_epc_features *epc_features;
+	unsigned long flags;
+
+	if (IS_ERR_OR_NULL(epc) || func_no >= epc->max_functions)
+		return NULL;
+
+	if (!epc->ops->get_features)
+		return NULL;
+
+	spin_lock_irqsave(&epc->lock, flags);
+	epc_features = epc->ops->get_features(epc, func_no);
+	spin_unlock_irqrestore(&epc->lock, flags);
+
+	return epc_features;
+}
+EXPORT_SYMBOL_GPL(pci_epc_get_features);
+
 /**
  * pci_epc_stop() - stop the PCI link
  * @epc: the link of the EPC device that has to be stopped