[RFC/RFT PATCH 03/18] PCI: Introduce pci_scan_root_bus_bridge()

[Lorenzo Pieralisi]

Current pci_scan_root_bus() interface is made up of two main
code paths:

- pci_create_root_bus()
- pci_scan_child_bus()

pci_create_root_bus() is a wrapper function that allows to create
a struct pci_host_bridge structure, initialize it with the passed
parameters and register it with the kernel.

As the struct pci_host_bridge require additional struct members,
pci_create_root_bus() parameters list has grown in time, making
it unwieldy to add further parameters to it in case the struct
pci_host_bridge gains more members fields to augment its functionality.

Since PCI core code provides functions to allocate struct
pci_host_bridge, instead of forcing the pci_create_root_bus() interface
to add new parameters to cater for new struct pci_host_bridge
functionality, it is more suitable to add an interface in PCI
core code to scan a PCI bus straight from a struct pci_host_bridge
created and customized by each specific PCI host controller driver.

Add a pci_scan_root_bus_bridge() function to allow PCI host controller
drivers to create and initialize struct pci_host_bridge and scan
the resulting bus.

Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
Cc: Arnd Bergmann <arnd at arndb.de>
Cc: Bjorn Helgaas <bhelgaas at google.com>
---
 drivers/pci/probe.c | 38 ++++++++++++++++++++++++++++++++++++++
 include/linux/pci.h |  1 +
 2 files changed, 39 insertions(+)

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 7e4ffc4..c7a7f72 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2412,6 +2412,44 @@ void pci_bus_release_busn_res(struct pci_bus *b)
 			res, ret ? "can not be" : "is");
 }
 
+int pci_scan_root_bus_bridge(struct pci_host_bridge *bridge)
+{
+	struct resource_entry *window;
+	bool found = false;
+	struct pci_bus *b;
+	int max, bus, ret;
+
+	if (!bridge)
+		return -EINVAL;
+
+	resource_list_for_each_entry(window, &bridge->windows)
+		if (window->res->flags & IORESOURCE_BUS) {
+			found = true;
+			break;
+		}
+
+	ret = pci_register_host_bridge(bridge);
+	if (ret < 0)
+		return ret;
+
+	b = bridge->bus;
+	bus = bridge->busnr;
+
+	if (!found) {
+		dev_info(&b->dev,
+		 "No busn resource found for root bus, will use [bus %02x-ff]\n",
+			bus);
+		pci_bus_insert_busn_res(b, bus, 255);
+	}
+
+	max = pci_scan_child_bus(b);
+
+	if (!found)
+		pci_bus_update_busn_res_end(b, max);
+
+	return 0;
+}
+
 struct pci_bus *pci_scan_root_bus_msi(struct device *parent, int bus,
 		struct pci_ops *ops, void *sysdata,
 		struct list_head *resources, struct msi_controller *msi)
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 99878a9..757779a 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -847,6 +847,7 @@ struct pci_bus *pci_scan_root_bus_msi(struct device *parent, int bus,
 struct pci_bus *pci_scan_root_bus(struct device *parent, int bus,
 					     struct pci_ops *ops, void *sysdata,
 					     struct list_head *resources);
+int pci_scan_root_bus_bridge(struct pci_host_bridge *bridge);
 struct pci_bus *pci_add_new_bus(struct pci_bus *parent, struct pci_dev *dev,
 				int busnr);
 void pcie_update_link_speed(struct pci_bus *bus, u16 link_status);
-- 
2.10.0