PCI: generic: Add pci_host_common_probe(), based on gen_pci_probe()

Factor gen_pci_probe(), moving most of it into pci_host_common_probe()
where it can be shared with other drivers that have slightly different
config accessors.  No functional change intended.

[bhelgaas: split into separate patch, changelog]
Signed-off-by: David Daney <david.daney@cavium.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Will Deacon <will.deacon@arm.com>

drivers/pci/host/pci-host-generic.c

@@ -182,19 +182,15 @@ static int gen_pci_parse_map_cfg_windows(struct gen_pci *pci)
 	return 0;
 }
 
-static int gen_pci_probe(struct platform_device *pdev)
+static int pci_host_common_probe(struct platform_device *pdev,
+				 struct gen_pci *pci)
 {
 	int err;
 	const char *type;
-	const struct of_device_id *of_id;
 	struct device *dev = &pdev->dev;
 	struct device_node *np = dev->of_node;
-	struct gen_pci *pci = devm_kzalloc(dev, sizeof(*pci), GFP_KERNEL);
 	struct pci_bus *bus, *child;
 
-	if (!pci)
-		return -ENOMEM;
-
 	type = of_get_property(np, "device_type", NULL);
 	if (!type || strcmp(type, "pci")) {
 		dev_err(dev, "invalid \"device_type\" %s\n", type);
@@ -203,8 +199,6 @@ static int gen_pci_probe(struct platform_device *pdev)
 
 	of_pci_check_probe_only();
 
-	of_id = of_match_node(gen_pci_of_match, np);
-	pci->cfg.ops = (struct gen_pci_cfg_bus_ops *)of_id->data;
 	pci->host.dev.parent = dev;
 	INIT_LIST_HEAD(&pci->host.windows);
 	INIT_LIST_HEAD(&pci->resources);
@@ -247,6 +241,21 @@ static int gen_pci_probe(struct platform_device *pdev)
 	return 0;
 }
 
+static int gen_pci_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	const struct of_device_id *of_id;
+	struct gen_pci *pci = devm_kzalloc(dev, sizeof(*pci), GFP_KERNEL);
+
+	if (!pci)
+		return -ENOMEM;
+
+	of_id = of_match_node(gen_pci_of_match, dev->of_node);
+	pci->cfg.ops = (struct gen_pci_cfg_bus_ops *)of_id->data;
+
+	return pci_host_common_probe(pdev, pci);
+}
+
 static struct platform_driver gen_pci_driver = {
 	.driver = {
 		.name = "pci-host-generic",